Search

Mendelian randomization (MR) is a method of studying the causal effects of modifiable exposures (i.e., potential risk factors) on health, social, and economic outcomes using genetic variants associated with the specific exposures of interest. MR provides a more robust understanding of the influence of these exposures on outcomes because germline genetic variants are randomly inherited from parents to offspring and, as a result, should not be related to potential confounding factors that influence exposure-outcome associations. The genetic variant can therefore be used as a tool to link the proposed risk factor and outcome, and to estimate this effect with less confounding and bias than conventional epidemiological approaches. We describe the scope of MR, highlighting the range of applications being made possible as genetic data sets and resources become larger and more freely available. We outline the MR approach in detail, covering concepts, assumptions, and estimation methods. We cover some common misconceptions, provide strategies for overcoming violation of assumptions, and discuss future prospects for extending the clinical applicability, methodological innovations, robustness, and generalizability of MR findings.

In this study we examine the instrument selection strategies currently used throughout the type 2 diabetes and HbA1c Mendelian randomization (MR) literature. We then argue for a more integrated and thorough approach, providing a framework to do this in the context of HbA1c and diabetes. We conducted a literature search for MR studies that have instrumented diabetes and/or HbA1c. We also used data from the UK Biobank (UKB) (N = 349,326) to calculate instrument strength metrics that are key in MR studies (the F statistic for average strength and R2 for total strength) with two different methods (“individual-level data regression” and Cragg-Donald formula). We used a 157–single nucleotide polymorphism (SNP) instrument for diabetes and a 51-SNP instrument (with partition into glycemic and erythrocytic as well) for HbA1c. Our literature search yielded 48 studies for diabetes and 22 for HbA1c. Our UKB empirical examples showed that irrespective of the method used to calculate metrics of strength and whether the instrument was the main one or included partition by function, the HbA1c genetic instrument is strong in terms of both average and total strength. For diabetes, a 157-SNP instrument was shown to have good average strength and total strength, but these were both substantially lesser than those of the HbA1c instrument. We provide a careful set of five recommendations to researchers who wish to genetically instrument type 2 diabetes and/or HbA1c. In MR studies of glycemia, investigators should take a more integrated approach when selecting genetic instruments, and we give specific guidance on how to do this.

There is a pressing need for novel drug targets for psychiatric disorders. Circulating proteins are potential candidates because they are relatively easy to measure and modulate and play important roles in signaling.We performed two-sample Mendelian randomization analyses to estimate the associations between circulating protein abundances and risk of 10 psychiatric disorders. Genetic variants associated with 1611 circulating protein abundances identified in 6 large-scale proteomic studies were used as genetic instruments. Effects of the circulating proteins on psychiatric disorders were estimated by Wald ratio or inverse variance-weighted ratio tests. Horizontal pleiotropy, colocalization, and protein-altering effects were examined to validate the assumptions of Mendelian randomization.Nine circulating protein-to-disease associations withstood multiple sensitivity analyses. Among them, 2 circulating proteins had associations replicated in 3 proteomic studies. A 1 standard deviation increase in the genetically predicted circulating TIMP4 level was associated with a reduced risk of anorexia nervosa (minimum odds ratio [OR] = 0.83; 95% CI, 0.76-0.91) and bipolar disorder (minimum OR = 0.88; 95% CI, 0.82-0.94). A 1 standard deviation increase in the genetically predicted circulating ESAM level was associated with an increased risk of schizophrenia (maximum OR = 1.32; 95% CI, 1.22-1.43). In addition, 58 suggestive protein-to-disease associations warrant validation with observational or experimental evidence. For instance, a 1 standard deviation increase in the ERLEC1-201-to-ERLEC1-202 splice variant ratio was associated with a reduced risk of schizophrenia (OR = 0.94; 95% CI, 0.90-0.97).Prioritized circulating proteins appear to influence the risk of psychiatric disease and may be explored as intervention targets.

Background: In a genome-wide association study of intracranial aneurysms (IA), enrichment was found between genes associated with IA and genes encoding targets of effective anti-epileptic drugs. Our aim was to assess if this pleiotropy is driven by shared disease mechanisms that could potentially highlight a treatment strategy for IA. Methods: Using 2-sample inverse-variance weighted Mendelian randomization and genetic colocalization analyses we assessed: (1) if epilepsy liability in general affects IA risk, and (2) whether changes in gene- and protein-expression levels of anti-epileptic drug targets in blood and arterial tissue may causally affect IA risk. Results: We found no overall effect of epilepsy liability on IA. Expression of 21 genes and 13 proteins corresponding to anti-epileptic drug targets supported a causal effect ( P CNNM2 levels showed strong evidence for colocalization with IA risk (posterior probability>70%). Higher CNNM2 levels in arterial tissue were associated with increased IA risk (odds ratio, 3.02; [95% CI, 2.32–3.94]; P =3.39×10 − 16 ). CNNM2 expression was best proxied by rs11191580. The magnitude of the effect of this variant was greater than would be expected if systemic blood pressure was the sole IA-causing mechanism in this locus. Conclusions: CNNM2 is a driver of the pleiotropy between IA and anti-epileptic drug targets. Administration of the anti-epileptic drugs phenytoin, valproic acid, or carbamazepine may be expected to decrease CNNM2 levels and therefore subsequently decrease IA risk. CNNM2 is therefore an important target to investigate further for its role in the pathogenesis of IA.

Alzheimer's disease (AD) is a progressive and fatal neurodegenerative disease caused by a combination of genetic and environmental risk factors. The serum metabolome refers to a set of small-molecules which are an important determinant of cellular health. We obtained genome-wide association study (GWAS) summary statistics for serum concentrations of 376 metabolites which were population matched with 2 GWAS studies of AD. For each metabolite we performed 2-sample MR (2SMR) using an inverse variance weighted (IVW) estimate for significance testing. After Bonferroni multiple testing correction one metabolite was causally linked to AD in both GWAS: serum urate. This result was supported by robust 2SMR measures and sensitivity analyses. We applied 2SMR to test for a causal relationship between serum urate and other neurodegenerative diseases: Parkinson disease (PD) and Amyotrophic lateral sclerosis (ALS). In ALS but not PD we identified a nominally significant link between serum urate and disease-risk, although in this case increased serum urate was protective. We conclude that serum urate is a modulator of risk for neurodegeneration. Our work has implications for the design of preventative interventions.

Previous studies have suggested a potential association between sleep and telomere length (TL), but its genetic basis remains unclear. In this study, we aimed to explore the genetic correlation and potential causal association between TL and insomnia.The genome-wide association study (GWAS) datasets of TL and insomnia-related traits were used, including insomnia, snoring, daytime dozing and napping. Based on the polygenic risk scores (PRS) of TL, linear regression and linkage disequilibrium score (LDSC) regression were used to preliminarily explore the association between TL and insomnia parameters in the UK Biobank cohort. Then, we investigated the causal association between TL and insomnia by mendelian randomization (MR) analysis and colocalization analysis.In the UK Biobank cohort, the association between TL and insomnia was observed in the female samples (t = 2.968, P = 3.00 × 10Our study found no evidence for causal association between insomnia and TL in individuals of European ancestry. We detected a candidate gene associated with both insomnia and TL, providing novel clues for understanding the roles of this association.

We investigated whether alcohol intake has a causal relationship with type 2 diabetes mellitus (T2DM) risk in adults of the Korean Genomic Epidemiology Study using two-sample Mendelian randomization (MR) analysis.Daily alcohol intake was calculated based on the type, average amount, and frequency of alcohol consumption for six months before the interview. The participants were divided into low- and high-alcohol intake of 20 g/day. After adjusting for the covariates related to T2DM, the independent genetic variants (instrumental variables) related to alcohol intake were explored by GWAS analysis in a city hospital-based cohort (n = 58,701). SNPs with a significant level of p-value5 × 10This study supports that heavy alcohol intake appears to be causally associated with T2DM risk.

Background: Inflammation is thought to be a risk factor for kidney disease. However, whether inflammatory status is either a cause or an outcome of chronic kidney disease remains controversial. We aimed to investigate the causal relationship between high-sensitivity C-reactive protein (hs-CRP) and estimated glomerular filtration rate (eGFR) using Mendelian randomization (MR) approaches. Methods: A total of 10,521 participants of the Japan Multi-institutional Collaborative Cohort Study was analyzed in this study. We used two-sample MR approaches (the inverse-variance weighted (IVW), the weighted median (WM), and the MR-Egger method) to estimate the effect of genetically determined hs-CRP on kidney function. We selected four and three hs-CRP associated single nucleotide polymorphisms (SNPs) as two instrumental variables (IV): IVCRP and IVAsian, based on SNPs previously identified in European and Asian populations. IVCRP and IVAsian explained 3.4% and 3.9% of the variation in hs-CRP, respectively. Results: Using the IVCRP, genetically determined hs-CRP was not significantly associated with eGFR in the IVW and the WM methods (estimate per 1 unit increase in ln(hs-CRP), 0.000; 95% confidence interval [CI], −0.019 to 0.020 and −0.003; 95% CI, −0.019 to 0.014, respectively). For IVAsian, we found similar results using the IVW and the WM methods (estimate, 0.005; 95% CI, −0.020 to 0.010 and −0.004; 95% CI, −0.020 to 0.012, respectively). The MR-Egger method also showed no causal relationships between hs-CRP and eGFR (IVCRP: −0.008; 95% CI, −0.058 to 0.042; IVAsian: 0.001; 95% CI, −0.036 to 0.036). Conclusion: Our two-sample MR analyses with different IVs did not support a causal effect of hs-CRP on eGFR.

Whether impaired kidney function is associated with increased risk of developing dementia is unclear. We investigated the association between estimated glomerular filtration rate (eGFR) and dementia. Using a triangulation approach, we performed (1) a prospective study in 90,369 Danes from the Copenhagen General Population Study (CGPS), (2) a meta-analysis in 468,699 Scandinavians (including CGPS) and (3) a two-sample Mendelian randomization study in 218,792-1,004,040 Europeans using summary data from largest publicly available genome wide association studies (GWASs). During up to 15 years of follow-up (CGPS), 2,468 individuals developed dementia. Age and sex standardized percentile of eGFR below versus above the median conferred a multifactorially adjusted hazard ratio of 1.09 (95% confidence interval: 1.01–1.18). In meta-analysis, random-effects risk of dementia was 1.14 (1.06–1.22) for mildly decreased eGFR (60–90 mL/min/1.73 m 2), 1.31 (0.92–1.87) for moderately decreased eGFR (30–59 mL/min/1.73 m 2) and 1.91 (1.21–3.01) for severely decreased eGFR (< 30 mL/min/1.73 m 2), compared to reference eGFR (> 90 mL/min/1.73 m 2). Using directly comparable eGFR measures (log[eGFR] scaled to one standard deviation, as well as eGFR below versus above 60 mL/min/1.73 m 2), we found no association with risk of dementia in observational CGPS or in Mendelian randomization analyses. In conclusion, impaired kidney function was associated with modestly increased risk of developing dementia. This was not supported by causal, genetic analyses using a Mendelian randomization approach. However, future stronger genetic instruments for kidney function and larger GWASs with more dementia cases, particularly for the vascular dementia subtype, warrant a re-evaluation of the causal hypothesis.

Observational studies have indicated that sedentary behavior is associated with myocardial infarction (MI), heart failure (HF), and atrial fibrillation (AF). Nevertheless, whether these associations are causal remain controversial, due to confounding factors (e.g., physical activity) and reverse causality.Instrumental variables were obtained from the largest genome-wide association studies of sedentary behavior (408,815 individuals) to date. We obtained summary statistics of MI from the CARDIoGRAMplusC4D consortium (171,875 individuals), HF from the HERMES Consortium (977,323 individuals), and AF from the Atrial Fibrillation Consortium (588,190 individuals). The inverse-variance weighted method was applied to obtain Mendelian randomization (MR) estimates, and other statistical methods were conducted in the sensitivity analyses. The main analyses were repeated using data from the FinnGen study. Multivariable MR analysis and mediation analysis were performed to evaluate the role of physical activity and other confounders. Genetically determined television watching was associated with MI (odds ratio [OR], 1.38; 95% CI, 1.19-1.59; p = 1.9 × 10Genetic liability to prolonged television watching is associated with higher risks of MI and HF. Interventions for reducing television watching time, such as public education and awareness campaigns, should be further investigated.

Lung cancer is a malignant tumor with a high incidence, it is vital to identify modifiable and avoidable risk factors for primary prevention, which can significantly lower the risk of cancer by preventing exposure to hazards and altering risky behavior. Some observational studies suggest that an increase in docosahexaenoic acid (DHA) consumption can reduce lung cancer risk. However, interpretation of these observational findings is difficult due to residual confounding or reverse causality. To evaluate the link between DHA and lung cancer, we have undertaken this analysis to examine the causal association between DHA and the risk of lung cancer using a two-sample Mendelian randomization (MR) framework.We performed a two-sample MR analysis to evaluate the causal effect of plasma DHA levels on lung cancer risk. For the exposure data, we extracted genetic variants as instrumental variables (IVs) that are strongly associated with DHA from a large-scale genome-wide association study (GWAS). We obtained the corresponding effect estimates for IVs on the risk of lung cancer with 11,348 cases and 15,861 controls. Finally, we applied Mendelian randomization analysis to obtain preliminary MR results and performed sensitivity analyses to verify the robustness of our results.According to the primary MR estimates and further sensitivity analyses, a higher serum DHA level was associated with a higher risk of lung cancer [OR = 1.159, 95% CI (1.04-1.30), P = 0.01]. For lung adenocarcinoma, the results also showed a close correlation between the DHA level and lung adenocarcinoma [OR = 1.277, 95% CI (1.09-1.50), P = 0.003], but it was not statistically significant for squamous cell carcinoma [OR = 1.071, 95% CI (0.89-1.29), P = 0.467].Our study revealed that plasma DHA is positively associated with the risk of lung cancer overall, especially for lung adenocarcinoma. This study provides new information to develop dietary guidelines for primary lung cancer prevention.

Alzheimer's disease (AD) is predicted to affect 132 million people by 2050. Targeting modifiable lifestyle risk factors that are associated with an increased risk of AD could prevent a large proportion of dementia cases, allowing people to reach the end of their life dementia free. However, evidence obtained from the observational studies does not take into account how risk factors are correlated with one another, and whether they causally contribute to increased AD risk. In this study, we determine whether the relationship between previously speculated AD risk factors and AD susceptibility is consistent with causality using large-scale genetic data. We focus on educational attainment (EA), intelligence and household income which have been previously shown to be causally associated with AD. Using GWAS-by-subtraction and Multivariable Mendelian Randomization we show that of these, only the cognitive component of EA (intelligence) is independently causally associated with AD. This work has ramifications for the modifiability of lifestyle risk factors for AD.

To provide some causal evidence concerning the effects of metformin on osteoarthritis (OA) using two metformin targets, namely AMP-activated protein kinase (AMPK) and growth differentiation factor 15 (GDF-15) as metformin proxies.This is a 2-sample Mendelian randomization design. We constructed 44 AMPK-related variants genetically predicted in HbA1c (%) as instruments for AMPK and five variants strongly predicted GDF-15 as instruments for GDF-15. Summary-level data for three OA phenotypes, including OA at any site, knee OA, and hip OA were obtained from the largest genome-wide meta-analysis across the UK Biobank and arcOGEN with 455,211 Europeans. Main analyses were conducted using the inverse-variance weighted method. Weighted median and MR-Egger were conducted as sensitivity analyses to assess the robustness of our results.Genetically predicted AMPK were negatively associated with OA at any site (OR: 0.60; 95% CI: 0.43-0.83) and hip OA (OR: 0.42; 95% CI: 0.22-0.80), but with not knee OA (OR: 0.85; 95% CI: 0.49-1.50). Higher levels of genetically predicted GDF-15 reduced the risk of hip OA (OR: 0.95; 95% CI: 0.90-0.99), but not OA at any site (OR: 1.00; 95% CI: 0.98-1.02) and knee OA (OR: 1.02; 95% CI: 0.98-1.07).This study indicates that AMPK and GDF-15 can be potential therapeutic targets for OA, especially for hip OA, and metformin would be repurposed for OA therapy which needs to be verified in randomized controlled trials.

The relationship between vitamin D and heart failure (HF) has attracted significant interest, but the association between the two in previous studies remains uncertain. Therefore, we used two-sample Mendelian randomization (MR) to investigate a causal association between 25-hydroxyvitamin D (25OHD) and HF risk.This study utilized summary statistics from the most extensive genome-wide association studies for 25OHD and HF. To make the results more reliable, we used several methods based on three assumptions for MR analysis. We also used the multivariable MR adjusting for hypertension, BMI, diabetes, chronic kidney disease to further elucidate the association between 25OHD and HF. Considering the potential pleiotropy, we performed an MR analysis with conditionally independent genetic instruments at core genes to further determine the relationship between vitamin D and heart failure. We found that per 1 SD increase in standardized log-transformed 25OHD level, the relative risk of HF decreased by 16.5% (OR: 0.835, 95% Cl: 0.743-0.938, P = 0.002), and other MR methods also showed consistent results. The multivariable MR also reported that per 1 SD increase in standardized log-transformed 25OHD level, the relative risk of HF decreased. And the scatter plots showed a trend towards an inverse MR association between 25OHD levels, instrumented by the core 25OHD genes, and HF.In summary, we found a potential inverse association between elevated 25OHD levels and the risk of HF, which suggested that timely 25OHD supplementation or maintaining adequate 25OHD concentrations may be an essential measure for HF prevention in the general population.

Objective Haematopoiesis was shown to regulate bone metabolism in in vivo studies. However, whether haematopoiesis has causal effects on bone health has never been investigated in humans. We aimed to evaluate the causal relationships of blood traits with bone mineral density (BMD) and fracture. Design and methods Using two-sample Mendelian randomization, causal relationship of 29 blood traits with estimated BMD (eBMD), total body BMD (TBBMD), lumbar spine BMD (LSBMD), femoral neck BMD (FNBMD) and fracture were evaluated by inverse-variance weighted (IVW) method and multiple sensitivity analyses. Relevant genetic data were obtained from the largest possible publicly available genome-wide association studies. Results Eight genetically determined red blood cell traits showed positive causal effects on eBMD, with beta estimates ranging from 0.009 (mean corpuscular haemoglobin) to 0.057 (haemoglobin concentration), while three white blood cell traits, including lymphocyte count (beta: −0.020; 95% CI: −0.033 to −0.007), neutrophil count (beta: −0.020; 95% CI: −0.035 to −0.006) and white blood cell count (beta: −0.027; 95% CI: −0.039 to −0.014), were inversely associated with eBMD. Causal effects for six of these blood traits were validated on TBBMD, LSBMD, FNBMD and/or fracture. The association of reticulocyte count (beta: 0.040; 95% CI: 0.016 to 0.063), haemoglobin (beta: 0.058; 95% CI: 0.021 to 0.094) and mean corpuscular haemoglobin concentration (beta: 0.030; 95% CI: 0.007 to 0.054) with eBMD remained significant in multivariable IVW analyses adjusted for other blood traits. Conclusion This study provided evidence that haematopoietic system might regulate the skeletal system in humans and suggested the possible pathophysiology of bone diseases among people with haematological diseases. Significance statement We conducted a novel Mendelian randomization study investigating the causal relationship of blood cells with bone mineral density. Red and white blood cell traits have positive and inverse causal relationship with bone mineral density, respectively, suggesting a potential link of haematopoietic system with the skeletal system in humans. Current findings suggest individuals with related haematological diseases, such as anaemia and leukocytosis, may have a lifelong increased risk of osteoporosis and/or fracture. Given that complete blood count is commonly performed in clinical setting, whether complete blood count can be used to predict fracture risk warrants further investigation.

Previous observational studies have shown that the levels of tumor necrosis factor (TNF) increased in patients with schizophrenia. The present two-sample Mendelian randomization (MR) study aims to identify the causal link between TNF and schizophrenia.To date, the largest genome-wide association study (GWAS) for TNF (n = 23 141) and for schizophrenia (53 386 cases and 77 258 controls) was used. All participants were of European ancestry. The MR-egger_intercept test and Cochran's Q statistic were used to determine the pleiotropy and heterogeneity, respectively. Weighted median and inverse variance weighted (IVW) were used to evaluate the causal association of TNF with schizophrenia.We found no significant pleiotropy or heterogeneity of all three selected plasma TNF genetic instrumental variants in breast cancer GWAS. Interestingly, the odds ratio (OR) = 1.517 with 95% confidence interval (CI), 1.006-2.288 and P = 0.047 of schizophrenia correspond to one unit increase in natural log-transformed TNF levels using IVW method. The increased trend was further proven using weighted median (OR = 1.585; 95% CI, 1.017-2.469; P = 0.042). Reverse MR analysis shows no causal effect of schizophrenia on plasma TNF levels.Our analysis suggested a causal association between genetically increased TNF signaling and increased risk of schizophrenia in the European population. Thus, TNF may be a potential risk for schizophrenia.

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), has been reported to be associated with an increased risk of coronary heart disease (CHD); however, the causal link between IBD and CHD is unclear. We performed Mendelian randomization (MR) analysis to investigate the association between genetically predicted IBD and CHD risk.Exposure summary data were obtained from genome-wide association studies (GWAS) with cohorts of IBD (12,882 cases and 21,770 controls), UC (6968 cases and 20,464 controls), and CD (5956 cases and 14,927 controls) of European descent to identify single nucleotide polymorphisms (SNPs) as instrumental variables. Outcome summary data were obtained from a meta-analysis of 22 GWAS including 22,233 cases and 64,762 controls of European descent. To estimate MR, four methods were used, including inverse variance-weighted (IVW), MR-Egger, simple mode, and weighted median methods. Sensitivity analysis was also performed. The Bonferroni method was used to correct the bias of multiple testing.Three sets of SNPs (69 SNPs of IBD, 40 SNPs of UC, and 58 SNPs of CD) were used to estimate the causal effect between genetically predicted IBD and CHD. Using the IVW method, we found that no causal relationship between genetically predicted IBD and CHD after Bonferroni correction, and there was no causal relationship between UC/CD and the development of CHD. No evidence of significant heterogeneity and pleiotropy was found.The results of this study suggested that genetically predicted IBD may have no causal effect on CHD risk in a population with European ancestry.

Aims/hypothesis Excess adiposity is differentially associated with increased risk of cardiometabolic disease in men and women, according to observational studies. Causal inference studies largely assume a linear relationship between BMI and cardiometabolic outcomes, which may not be the case. In this study, we investigated the shapes of the causal relationships between BMI and cardiometabolic diseases and risk factors. We further investigated sex differences within the causal framework. Methods To assess causal relationships between BMI and the outcomes, we used two-stage least-squares Mendelian randomisation (MR), with a polygenic risk score for BMI as the instrumental variable. To elucidate the shapes of the causal relationships, we used a non-linear MR fractional polynomial method, and used piecewise MR to investigate threshold relationships and confirm the shapes. Results BMI was associated with type 2 diabetes (OR 3.10; 95% CI 2.73, 3.53), hypertension (OR 1.53; 95% CI 1.44, 1.62) and coronary artery disease (OR 1.20; 95% CI 1.08, 1.33), but not chronic kidney disease (OR 1.08; 95% CI 0.67, 1.72) or stroke (OR 1.08; 95% CI 0.92, 1.28). The data suggest that these relationships are non-linear. For cardiometabolic risk factors, BMI was positively associated with glucose, HbA1c, triacylglycerol levels and both systolic and diastolic BP. BMI had an inverse causal relationship with total cholesterol, LDL-cholesterol and HDL-cholesterol. The data suggest a non-linear causal relationship between BMI and BP and other biomarkers (pp Conclusions/interpretation We describe the shapes of causal effects of BMI on cardiometabolic diseases and risk factors, and report sex differences in the causal effects of BMI on LDL-cholesterol. We found evidence of non-linearity in the causal effect of BMI on diseases and risk factor biomarkers. Reducing excess adiposity is highly beneficial for health, but there is greater need to consider biological sex in the management of adiposity. Graphical abstract

Background Glutamine family amino acids such as glutamate, pyroglutamate, and glutamine have been shown to play important roles in COVID-19. However, it is still unclear about the role of pyroglutamate in COVID-19. Thus, we use a two-sample Mendelian randomization (MR) study to identify the genetic causal link between blood pyroglutamine levels and COVID-19 risk. Methods Pyroglutamine genetic instrumental variables (IVs) were chosen from the largest pyroglutamine-associated genome-wide association studies (GWAS). The largest COVID-19 GWAS dataset was employed to evaluate the causal link between blood pyroglutamine levels and COVID-19 risk using two-sample MR analysis. Results We found no significant pleiotropy or heterogeneity of pyroglutamine-associated genetic IVs in COVID-19 GWAS. Interestingly, we found that as pyroglutamine genetically increased, the risk of COVID-19 decreased using inverse variance weighted (IVW) (Beta = − 0.644, p = 0.003; OR = 0.525, 95% CI [0.346–0.798]) and weighted median (Beta = − 0.609, p = 0.013; OR = 0.544, 95% CI [0.337–0.878]). Conclusion Our analysis suggests a causal link between genetically increased pyroglutamine and reduced risk of COVID-19. Thus, pyroglutamine may be a protective factor for patients with COVID-19.

Circulating metabolites have been implicated in stroke pathogenesis, but their genetic determinants are understudied. Using a Mendelian randomization approach, our aim was to provide evidence for the relationship of circulating metabolites and the risk of stroke and its subtypes.Genetic instruments of 102 circulating metabolites were obtained from a genome-wide association study, including 24,925 European individuals. Stroke was extracted from the MEGASTROKE dataset (67,162 cases; 454,450 controls) and a lacunar stroke dataset (7338 cases; 254,798 controls). The magnetic resonance imaging markers of cerebral small vessel disease and microstructural injury were evaluated by a genome-wide association study of white matter hyperintensities (N = 18,381), fractional anisotropy (N = 17,663), mean diffusivity (N = 17,467) and brain microbleeds (N = 25,862). The inverse-variance weighted method Mendelian randomization was used as the primary analytical method, and directional pleiotropy and heterogeneity were examined in sensitivity analyses.A genetic predisposition to a higher level of cholesterol in small and low-density lipoprotein (LDL) was associated with risk of stroke (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.08-1.21, p = 5.98 × 10Genetically determined levels of lipids in small LDL were associated with the risk of stroke, suggesting that a therapeutic strategy targeting small LDL levels may be crucial for stroke prevention. HDL-C was positively associated with the risk of intracerebral haemorrhage.

Although an association between type 1 diabetes (T1D) and hypothyroidism has been found in multiple observational studies, whether T1D plays a causal role in the development of hypothyroidism remains uncertain. Therefore, this Mendelian randomization (MR) study aimed to investigate the causal association between T1D and hypothyroidism.Independent single-nucleotide polymorphisms associated with T1D with genome-wide significance were selected as instrumental variables from a large genome-wide association study (GWAS) of T1D. Hypothyroidism GWAS summary statistics were obtained from the Thyroidomics Consortium. The inverse-variance weighted (IVW) method was used as the primary analysis for estimating the effect of the exposure on the outcome. We also used MR-Egger, the weighted median method, MR-Robust, and other methods to confirm the results.T1D had a positive causal association with hypothyroidism [IVW, odds ratio (OR) = 1.083, 95% confidence interval (CI), 1.046-1.122; p lt; .001]. MR-Egger regression indicated that directional pleiotropy did not bias the result (intercept = 0.006; p = .295). The causal association was verified in an independent validation set (IVW, OR = 1.099, 95% CI, 1.018-1.186; p = .017). The results were robust according to various MR methods, and the results of the reverse MR analysis did not support reverse causation (p gt; .05).The MR analysis results indicated a causal association between T1D and hypothyroidism. Therefore, it is recommended that patients with T1D undergo thyroid function tests regularly to minimize the risk of undiagnosed hypothyroidism among young patients with T1D.

Context Vitamin D (Vit-D), parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23) are the major calciotropic hormones involved in the regulation of blood calcium levels from the intestine, kidney, and bone through a tight endocrine feedback loop system. Altered levels of calcium itself or through the effect of its regulatory hormones could affect blood pressure (BP), but the exact mechanisms remain unclear. Objective To evaluate whether a causal relationship exists between serum calcium level and/or the regulatory hormones involved in its homeostasis with BP, we performed a two-sample Mendelian randomization (MR) study. Methods From 4 large genome-wide association studies (GWAS) we obtained independent (r2 < 0.001) single nucleotide polymorphisms (SNPs) associated with serum calcium (119 SNPs), Vit-D (78 SNPs), PTH (5 SNPs), and FGF23 (5 SNPs), to investigate through MR their association with systolic BP (SBP) and diastolic BP (DBP) in a Swedish urban-based study, the Malmö Diet and Cancer study (n = 29 298). Causality was evaluated by the inverse variance weighted method (IVW) and weighted median, while MR Egger and MR-PRESSO were used as sensitivity analyses. Results Genetically predicted serum calcium level was found to be associated with DBP (IVW: beta = 0.10, SE = 0.04, P = 0.007) and SBP (IVW: beta = 0.07, SE = 0.04, P = 0.04). Genetically predicted Vit-D and PTH showed no association with the traits, while FGF23 was inversely associated with SBP (IVW: beta = −0.11, SE = 0.04, P = 0.01), although this association lost statistical significance in sensitivity analysis. Conclusion Our study shows a direct association between genetically predicted calcium level and DBP, and a weaker association with SBP. No such clear association was found for genetically predicted calciotropic hormone levels. It is of interest to detect which target genes involved in calcium homeostasis mediate the effect of calcium on BP, particularly for improving personalized intervention strategies.

Colorectal cancer is the third most common and second most deadly type of cancer worldwide, with approximately 1.9 million cases and 0.9 million deaths worldwide in 2020. Previous studies have shown that estrogen and testosterone hormones are associated with colorectal cancer risk and mortality. However, the potential effect of their precursor, dehydroepiandrosterone sulfate (DHEAS), on colorectal cancer risk has not been investigated. Therefore, evaluating DHEAS’s effect on colorectal cancer will expand our understanding of the hormonal contribution to colorectal cancer risk. In this study, we conducted a two-sample Mendelian randomization (MR) analysis to investigate the causal effect of DHEAS on colorectal cancer. We obtained DHEAS and colorectal cancer genomewide association study (GWAS) summary statistics from the Leipzig Health Atlas and the GWAS catalog and conducted MR analyses using the TwoSampleMR R package. Our results suggest that higher DHEAS levels are causally associated with decreased colorectal cancer risk (odds ratio per unit increase in DHEAS levels z score = 0.70; 95% confidence interval [0.51, 0.96]), which is in line with previous observations in a case–control study of colon cancer. The outcome of this study will be beneficial in developing plasma DHEAS-based biomarkers in colorectal cancer. Further studies should be conducted to interpret the DHEAS-colorectal cancer association among different ancestries and populations.

Background and Purpose: The aim of this study was to investigate the association between daytime napping frequency and the incidence of essential hypertension or stroke as well as to validate causality in this relationship via Mendelian randomization (MR). Methods: We conducted Cox regression analysis on 358 451 participants free of hypertension or stroke from UK Biobank. To validate the results of the observational analysis, we conducted a 2-sample MR for daytime napping frequency (123 single-nucleotide polymorphisms) with essential hypertension in FinnGen Biobank, stroke, and ischemic stroke in MEGASTROKE consortium and performed a corresponding 1-sample MR on the UK Biobank data. Results: Compared with never napping, usually napping was associated with a higher risk of essential hypertension (hazard ratio, 1.12 [95% CI, 1.08–1.17]), stroke (hazard ratio, 1.24 [95% CI, 1.10–1.39], and ischemic stroke (hazard ratio, 1.20 [95% CI, 1.05–1.36]) in our prospective observational analysis. Both the 1-sample and 2-sample MR results indicated that increased daytime napping frequency was likely to be a potential causal risk factor for essential hypertension in FinnGEN (odds ratio, 1.43 [95% CI, 1.06–1.92]) and UK Biobank (odds ratio, 1.40 [95% CI, 1.28–1.58]). The 2-sample MR results supported the potential causal effect of nap frequency on ischemic stroke in MEGASTROKE (odds ratio, 1.29 [95% CI, 1.04–1.62]). Conclusions: Prospective observational and MR analyses provided evidence that increased daytime nap frequency may represent a potential causal risk factor for essential hypertension. The potential causal association of increased nap frequency with ischemic stroke was supported by 2-sample MR and prospective observational results.

Periconception folic acid supplementation has been suggested to protect against congenital heart disease (CHD), but the association between maternal red blood cell (RBC) folate, the gold-standard biomarker of folate exposure, and subsequent offspring CHD risk is lacking.To quantify the association between periconception maternal RBC folate and offspring CHD risk.Prospective, nested, case-control study and 1-sample Mendelian randomization. (ClinicalTrials.gov: NCT02737644).29 maternity institutions in 12 districts of Greater Shanghai, China.All 197 mothers of offspring with CHD and 788 individually matched mothers of unaffected offspring from the SPCC (Shanghai Preconception Cohort).Maternal RBC folate was measured before or at early pregnancy. Odds ratios [ORs] were estimated using conditional logistic regression after adjustment for covariates. Mendelian randomization was done using the methylenetetrahydrofolate reductase (Case patients had lower median maternal RBC folate concentrations than control participants (714 nmol/L [interquartile range, 482 to 1008 nmol/L] vs. 788 nmol/L [557 to 1094 nmol/L]). Maternal RBC folate concentrations were inversely associated with offspring CHD (adjusted OR per 100 nmol/L, 0.93 [95% CI, 0.89 to 0.99]). The adjusted OR for mothers with periconception RBC folate of 906 nmol/L or more (vs.906 nmol/L) was 0.61 (CI, 0.40 to 0.93). Mendelian randomization showed that each 100-nmol increase in maternal RBC folate concentrations was significantly associated with reduced offspring CHD risk (OR, 0.75 [CI, 0.61 to 0.92]).Potential confounding due to unmeasured covariates in the nested case-control study.Higher maternal RBC folate is associated with reduced offspring CHD risk. For primary CHD prevention, higher target RBC folate levels than currently recommended for neural tube defect prevention may be needed and warrant further study.National Key Research and Development Program of China, National Natural Science Foundation of China, China Postdoctoral Science Foundation, and Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences.

Age at natural menopause (ANM) is associated with a range of health-related traits, including bone health, female reproductive cancers, and cardiometabolic health. Our objective was to conduct a Mendelian randomization phenome-wide association study (MR-pheWAS) of ANM. We conducted a hypothesis-free analysis of the genetic risk score (GRS) for ANM with 18,961 health-related traits among 181,279 women in UK Biobank. We also stratified the GRS according to the involvement of SNPs in DNA damage response. We sought to replicate our findings in independent cohorts. We conducted a negative control MR-pheWAS among men. Among women, we identified potential effects of ANM on 221 traits (1.17% of all traits) at a false discovery rate (P value ≤ 5.83 × 10–4), and 91 (0.48%) potential effects when using Bonferroni threshold (P value ≤ 2.64 × 10–6). Our findings included 55 traits directly related to ANM (e.g. hormone replacement therapy, gynaecological conditions and menstrual conditions), and liver function, kidney function, lung function, blood-cell composition, breast cancer and bone and cardiometabolic health. Replication analyses confirmed that younger ANM was associated with HbA1c (adjusted mean difference 0.003 mmol/mol; 95% CI 0.001, 0.006 per year decrease in ANM), breast cancer (adjusted OR 0.96; 95% CI 0.95, 0.98), and bone-mineral density (adjusted mean difference − 0.05; 95% CI − 0.07, − 0.03 for lumbar spine). In men, 30 traits were associated with the GRS at a false discovery rate (P value ≤ 5.49 × 10–6), and 11 potential effects when using Bonferroni threshold (P value ≤ 2.75 × 10–6). In conclusion, our results suggest that younger ANM has potential causal effects on a range of health-related traits.

ImportanceRefractive error (RE) is the most common form of visual impairment, and myopic RE is associated with an increased risk of primary open-angle glaucoma (POAG). Whether this association represents a causal role of RE in the etiology of POAG remains unknown.ObjectiveTo evaluate shared genetic influences and investigate the association of myopic RE with the risk for POAG.Design, Setting, and ParticipantsObservational analyses were used to evaluate the association between mean spherical equivalent (MSE) RE (continuous trait) or myopia (binary trait) and POAG risk in individuals from the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort. To quantify genetic overlap, genome-wide genetic correlation analyses were performed using genome-wide association studies (GWAS) of MSE RE or myopia and POAG from GERA. Potential causal effects were assessed between MSE RE and POAG using 2-sample Mendelian randomization. Genetic variants associated with MSE RE were derived using GWAS summary statistics from a GWAS of RE conducted in 102 117 UK Biobank participants. For POAG, we used GWAS summary statistics from our previous GWAS (3836 POAG cases and 48 065 controls from GERA). Data analyses occurred between July 2020 and October 2021.Main Outcomes and MeasureOur main outcome was POAG risk as odds ratio (OR) caused by per-unit difference in MSE RE (in diopters).ResultsOur observational analyses included data for 54 755 non-Hispanic White individuals (31 926 [58%] females and 22 829 [42%] males). Among 4047 individuals with POAG, mean (SD) age was 73.64 (9.20) years; mean (SD) age of the 50 708 controls was 65.38 (12.24) years. Individuals with POAG had a lower refractive MSE and were more likely to have myopia or high myopia compared with the control participants (40.2% vs 34.1%, P = 1.31 × 10−11 for myopia; 8.5% vs 6.8%, P = .004 for high myopia). Our genetic correlation analyses demonstrated that POAG was genetically correlated with MSE RE (rg, −0.24; SE, 0.06; P = 3.90 × 10−5), myopia (rg, 0.21; SE, 0.07; P = .004), and high myopia (rg, 0.23; SE, 0.09; P = .01). Genetically assessed refractive MSE was negatively associated with POAG risk (inverse-variance weighted model: OR per diopter more hyperopic MSE = 0.94; 95% CI, 0.89-0.99; P = .01).Conclusions and RelevanceThese findings demonstrate a shared genetic basis and an association between myopic RE and POAG risk. This may support population POAG risk stratification and screening strategies, based on RE information.

IMPORTANCE Although hypothesis-driven research has identified several factors associated with psychosis, this one-exposure-to-one-outcome approach fails to embrace the multiplicity of exposures. Systematic approaches, similar to agnostic genome-wide analyses, are needed to identify genuine signals.OBJECTIVE To systematically investigate nongenetic correlates of psychotic experiences through data-driven agnostic analyses and genetically informed approaches to evaluate associations.DESIGN, SETTING, PARTICIPANTS This cohort study analyzed data from the UK Biobank Mental Health Survey from January 1 to June 1, 2021. An exposome-wide association study was performed in 2 equal-sized split discovery and replication data sets. Variables associated with psychotic experiences in the exposome-wide analysis were tested in a multivariable model. For the variables associated with psychotic experiences in the final multivariable model, the single-nucleotide variant-based heritability and genetic overlap with psychotic experiences using linkage disequilibrium score regression were estimated, and mendelian randomization (MR) approaches were applied to test potential causality. The significant associations observed in 1-sample MR analyses were further tested in multiple sensitivity tests, including collider-correction MR, 2-sample MR, and multivariable MR analyses.EXPOSURES After quality control based on a priori criteria, 247 environmental, lifestyle, behavioral, and economic variables.MAIN OUTCOMES AND MEASURES Psychotic experiences.RESULTS The study included 155 247 participants (87 896 [57%) female; mean [SD] age, 55.94 [7.74] years). In the discovery data set, 162 variables (66%) were associated with psychotic experiences. Of these, 148 (91%) were replicated. The multivariable analysis identified 36 variables that were associated with psychotic experiences. Of these, 28 had significant genetic overlap with psychotic experiences. One-sample MR analyses revealed forward associations with 3 variables and reverse associations with 3. Forward associations with ever having experienced sexual assault and pleiotropy of risk-taking behavior and reverse associations without pleiotropy of experiencing a physically violent crime as well as cannabis use and the reverse association with pleiotropy of worrying too long after embarrassment were confirmed in sensitivity tests. Thus, associations with psychotic experiences were found with both well-studied and unexplored multiple correlated variables. For several variables, the direction of the association was reversed in the final multivariable and MR analyses.CONCLUSIONS AND RELEVANCE The findings of this study underscore the need for systematic approaches and triangulation of evidence to build a knowledge base from ever-growing observational data to guide population-level prevention strategies for psychosis.

The existing framework of Mendelian randomization (MR) infers the causal effect of one or multiple exposures on one single outcome. It is not designed to jointly model multiple outcomes, as would be necessary to detect causes of more than one outcome and would be relevant to model multimorbidity or other related disease outcomes. Here, we introduce Multi-response Mendelian randomization (MR2), a novel MR method specifically designed for multiple outcomes to identify exposures that cause more than one outcome or, conversely, exposures that exert their effect on distinct responses. MR2uses a sparse Bayesian Gaussian copula regression framework to detect causal effects while estimating the residual correlation between summary-level outcomes, i.e., the correlation that cannot be explained by the exposures, andviceversa. We show both theoretically and in a comprehensive simulation study how unmeasured shared pleiotropy induces residual correlation. We also reveal how non-genetic factors that affect more than one outcome contribute to their correlation. We demonstrate that by accounting for residual correlation, MR2has higher power to detect shared exposures causing more than one outcome. It also provides more accurate causal effect estimates than existing methods that ignore the dependence between related responses. Finally, we illustrate how MR2detects shared and distinct causal exposures for five cardiovascular diseases in two applications considering cardiometabolic and lipidomic exposures and uncovers residual correlation between summary-level outcomes reflecting known relationships between cardiovascular diseases.

Non-linear Mendelian randomization is an extension to standard Mendelian randomization to explore the shape of the causal relationship between an exposure and outcome using an instrumental variable. The approach divides the population into strata and calculates separate instrumental variable estimates in each stratum. However, the standard implementation of stratification in non-linear Mendelian randomization, referred to as the residual method, relies on strong parametric assumptions of linearity and homogeneity between the instrument and the exposure to form the strata. If these stratification assumptions are violated, the instrumental variable assumptions may be violated in the strata even if they are satisfied in the population, resulting in misleading estimates. We propose a new stratification method, referred to as the doubly-ranked method, that does not require strict parametric assumptions to create strata with different average levels of the exposure such that the instrumental variable assumptions are satisfied within the strata. Our simulation study indicates that the doubly-ranked method can obtain unbiased stratum-specific estimates and appropriate coverage rates even when the effect of the instrument on the exposure is non-linear or heterogeneous. Moreover, it can also provide unbiased estimates when the exposure is coarsened (that is, rounded, binned into categories, or truncated), a scenario that is common in applied practice and leads to substantial bias in the residual method. We applied the proposed doubly-ranked method to investigate the effect of alcohol intake on systolic blood pressure, and found evidence of a positive effect of alcohol intake, particularly at higher levels of alcohol consumption.

AimsAlthough highly heritable, the genetic etiology of calcific aortic stenosis (AS) remains incompletely understood. The aim of this study was to discover novel genetic contributors to AS and to integrate functional, expression, and cross-phenotype data to identify mechanisms of AS.Methods and resultsA genome-wide meta-analysis of 11.6 million variants in 10 cohorts involving 653 867 European ancestry participants (13 765 cases) was performed. Seventeen loci were associated with AS at P ≤ 5 × 10-8, of which 15 replicated in an independent cohort of 90 828 participants (7111 cases), including CELSR2-SORT1, NLRP6, and SMC2. A genetic risk score comprised of the index variants was associated with AS [odds ratio (OR) per standard deviation, 1.31; 95% confidence interval (CI), 1.26-1.35; P = 2.7 × 10-51] and aortic valve calcium (OR per standard deviation, 1.22; 95% CI, 1.08-1.37; P = 1.4 × 10-3), after adjustment for known risk factors. A phenome-wide association study indicated multiple associations with coronary artery disease, apolipoprotein B, and triglycerides. Mendelian randomization supported a causal role for apolipoprotein B-containing lipoprotein particles in AS (OR per g/L of apolipoprotein B, 3.85; 95% CI, 2.90-5.12; P = 2.1 × 10-20) and replicated previous findings of causality for lipoprotein(a) (OR per natural logarithm, 1.20; 95% CI, 1.17-1.23; P = 4.8 × 10-73) and body mass index (OR per kg/m2, 1.07; 95% CI, 1.05-1.9; P = 1.9 × 10-12). Colocalization analyses using the GTEx database identified a role for differential expression of the genes LPA, SORT1, ACTR2, NOTCH4, IL6R, and FADS.ConclusionDyslipidemia, inflammation, calcification, and adiposity play important roles in the etiology of AS, implicating novel treatments and prevention strategies.

Data de publicació electrònica: 11-03-2023 There is evidence linking ADHD to a reduced life expectancy. The mortality rate in individuals with ADHD is twice that of the general population and it is associated with several factors, such as unhealthy lifestyle behaviors, social adversity, and mental health problems that may in turn increase mortality rates. Since ADHD and lifespan are heritable, we used data from genome-wide association studies (GWAS) of ADHD and parental lifespan, as proxy of individual lifespan, to estimate their genetic correlation, identify genetic loci jointly associated with both phenotypes and assess causality. We confirmed a negative genetic correlation between ADHD and parental lifespan (rg = −0.36, P = 1.41e−16). Nineteen independent loci were jointly associated with both ADHD and parental lifespan, with most of the alleles that increased the risk for ADHD being associated with shorter lifespan. Fifteen loci were novel for ADHD and two were already present in the original GWAS on parental lifespan. Mendelian randomization analyses pointed towards a negative causal effect of ADHD liability on lifespan (P = 1.54e−06; Beta = −0.07), although these results were not confirmed by all sensitivity analyses performed, and further evidence is required. The present study provides the first evidence of a common genetic background between ADHD and lifespan, which may play a role in the reported effect of ADHD on premature mortality risk. These results are consistent with previous epidemiological data describing reduced lifespan in mental disorders and support that ADHD is an important health condition that could negatively affect future life outcomes. This work was supported by the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR, 2017SGR-00444 and 2017SGR-1461), the Instituto de Salud Carlos III (PI18/01788, P19/01224, PI20/00041, PI21/00612, PI22/00464, FI18/00285 to LVR and CP22/00128 to MSA), the Ministry of Science, Innovation and Universities (IJC2018-035346-I to MSA and RYC2021-031324-I to JCD); the European Regional Development Fund (ERDF), the European Union H2020 Programme (H2020/2014–2020) under grant agreements no. 728018 (Eat2beNICE), no. 848228 (DISCOvERIE) and no. 2020604 (TIMESPAN) and the ECNP Network ‘ADHD across the Lifespan’ and “la Marató de TV3” (202228-30 and 202228-31). SSR was supported by funds from the California Tobacco-Related Disease Research Program (TRDRP; Grant Number T29KT0526 and T32IR5226), and NIH/NIDA DP1DA054394. AAP was supported by NIH grant P50DA037844 and R01AA029688 and Tobacco-Related Disease Research Program Grant number: 28IR-0070.

The associations between blood lipids, including total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides, and low-density lipoprotein cholesterol (LDL-C), and colorectal cancer risk are controversial. We evaluated potential causal relationships between blood lipids and colorectal cancer risk. Using the baseline data from the Japanese Consortium of Genetic Epidemiology studies, we estimated the single-nucleotide polymorphism (SNP)–exposure associations (n = 34,546 for TC, n = 50,290 for HDL-C, n = 51,307 for triglycerides, and n = 30,305 for LDL-C). We also estimated the SNP–outcome associations in another Japanese dataset (n = 7,936 colorectal cancer cases and n = 38,042 controls). We conducted Mendelian randomization (MR) analyses for the association between each blood lipid type and the risk of colorectal cancer using an inverse variance-weighted method. The total variances explained by the selected SNPs in TC (68 SNPs), HDL-C (50 SNPs), log-transformed triglycerides (26 SNPs), and LDL-C (35 SNPs) were 7.0%, 10.0%, 6.2%, and 5.7%, respectively. The odds ratios for colorectal cancer were 1.15 [95% confidence interval (CI), 1.01–1.32] per 1 standard deviation (SD; 33.3 mg/dL) increase in TC, 1.11 (95% CI, 0.98–1.26) per 1 SD (15.4 mg/dL) increase in HDL-C, 1.06 (95% CI, 0.90–1.26) per 1 SD (0.5 log-mg/dL) increase in log-transformed triglycerides, and 1.17 (95% CI, 0.91–1.50) per 1 SD (29.6 mg/dL) increase in LDL-C. Sensitivity analyses consistently suggested the positive association between TC and colorectal cancer, whereas results of each lipid component were inconsistent. In conclusion, this large MR study of a Japanese population showed a potentially causal association between high TC and colorectal cancer risk, although the association between each lipid component and colorectal cancer remained inconclusive. Prevention Relevance: In this large MR analysis of a Japanese population, a positive association was found between genetically predicted high total cholesterol (TC) levels and an increased risk of colorectal cancer. Therefore, lowering TC levels by lifestyle modifications or medications may be justified for the purpose of preventing colorectal cancer.

Observational studies have reported inconsistent results on the relationship between age-related macular degeneration (AMD) and Alzheimer's disease (AD). Therefore, we aimed to determine whether there is a causal association between AMD and AD.This two-sample bidirectional Mendelian randomization (MR) study evaluated causal associations between advanced AMD and AD using summary data from large genome-wide association studies.Genetic liability for advanced AMD showed no statistical causal association with AD risk (odds ratio [OR] = 0.999, 95% confidence interval [CI]: 0.955-1.044, P = .948). Reverse MR analysis provided little support for a causal effect of AD on advanced AMD (OR = 0.973, 95%CI: 0.938-1.008, P = .133).This MR study found no evidence to support a bidirectional causality between advanced AMD and AD.We evaluated the bidirectional causal relationship between advanced AMD and AD. Advanced AMD showed no statistical causal association with risk of AD. We found no evidence to support a causal effect of AD on advanced AMD risk. The associations observed in epidemiological studies should not be considered causal.

Obesity is associated with coronary artery disease (CAD) and its risk factors in observational studies. This two-sample Mendelian randomization (MR) study investigated the effect of visceral adipose tissue (VAT) mass on coronary artery disease (CAD), myocardial infarction (MI) and heart failure (HF).Genetic variants (220 SNPs, P 5 × 10Our results showed that genetically predicted higher VAT mass was associated with increased risk of CAD (odds ratio [OR] 1.57, 95% confidence interval [CI], 1.44-1.71; P = 7.62 × 10This MR study suggests that genetic determinants of VAT mass are causally associated with CAD, MI and HF.

Sleep disturbances have been linked with Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS) in observational studies, and the comorbidity of PD and ALS has been reported in clinical case reports, but the causalities remain unclear. This study aims to examine bidirectional causal relationships between sleep traits, PD and ALS.Bidirectional two sample Mendelian randomisation (MR) analyses were conducted, with data from individuals of mainly European ancestry. Genetic instruments were obtained from the largest published genome-wide association studies (GWAS) concerning various sleep traits, PD and ALS. MR estimates from each genetic instrument were combined by inverse variance weighted method, with alternate methods (eg, weighted median, MR Egger, MR-PRESSO) and statistical graphs to assess horizontal pleiotropy and remove outliers.MR analysis failed to observe any causal association between sleep disorders and PD, but found a possible causal effect of PD risk on ALS risk (odds ratio [OR] = 1.07; 95% CI: 1.01-1.14, P 0.01), albeit with a horizontal pleiotropy. Furthermore, MR analyses indicated that excessive daytime sleepiness (EDS) (OR = 2.29; 95% CI: 1.04-5.03, P = 0.04) contributed to a modest increase in risk of ALS, but the reverse causalities were not significant. Higher risk of ALS may be associated with being a "morning person" (OR = 1.03, P = 0.02), a longer sleep duration (OR = 1.01, P 0.01), and a mean of 9 h or more total sleep duration (β = 0.02, P = 0.04).Aided by large-scale GWAS, a shortage of evidence supporting causal relationships of sleep traits and PD risk, while significant evidence supports that EDS, higher PD risk may causally influence ALS risk. Future researches are required to explore the underlying pathological mechanism as well as the clinically significance, and replicate our findings using independent samples when data become available.

Observational studies reported conflicting results regarding the association between circulating concentrations of nutrition-related factors and atrial fibrillation (AF). The aim of this study was to evaluate the potential causal effect of 8 circulating nutrition-related factors (vitamin B12, vitamin E, folate, retinol, β-carotene, iron, zinc, and copper) on AF risk using mendelian randomization (MR). Summary-level data for the nutrition-related factors and AF were obtained from genome-wide association studies conducted among individuals of European ancestry. The genome-wide association study on AF included 60,620 cases and 970,216 controls. A 2-sample MR design was applied for evaluating the causal association. In the primary MR analyses, the inverse variance-weighted method did not identify any causal effect of circulating concentrations of vitamin B12 [β = 0.000, standard error (SE) = 0.021, P = 0.994], vitamin E (β = 0.080, SE = 0.152, P = 0.600), retinol (β = 0.098, SE = 0.397, P = 0.806), folate (β = -0.006, SE = 0.052, P = 0.901), β-carotene (β = 0.014, SE = 0.025, P = 0.560), iron (β = -0.009, SE = 0.072, P = 0.905), zinc (β = 0.038, SE = 0.032, P = 0.239), and copper (β = -0.012, SE = 0.023, P = 0.589) on AF. The MR-Egger and MR pleiotropy residual sum and outlier (MR-PRESSO) analyses did not suggest the presence of pleiotropy. In addition, the lack of association remained in the leave-one-out analysis. This MR study indicates no causal association of circulating concentrations of vitamin B12, vitamin E, folate, retinol, β-carotene, iron, zinc, and copper with AF.

We systematically investigated the bidirectional causality among HDL cholesterol (HDL-C), LDL cholesterol (LDL-C), triglycerides (TGs), fasting insulin (FI), and glycated hemoglobin A1c (HbA1c) based on genome-wide association summary statistics of Europeans (n = 1,320,016 for lipids, 151,013 for FI, and 344,182 for HbA1c). We applied multivariable Mendelian randomization (MR) to account for the correlation among different traits and constructed a causal graph with 13 significant causal effects after adjusting for multiple testing (P < 0.0025). Remarkably, we found that the effects of lipids on glycemic traits were through FI from TGs (β = 0.06 [95% CI 0.03, 0.08] in units of 1 SD for each trait) and HDL-C (β = −0.02 [−0.03, −0.01]). On the other hand, FI had a strong negative effect on HDL-C (β = −0.15 [−0.21, −0.09]) and positive effects on TGs (β = 0.22 [0.14, 0.31]) and HbA1c (β = 0.15 [0.12, 0.19]), while HbA1c could raise LDL-C (β = 0.06 [0.03, 0.08]) and TGs (β = 0.08 [0.06, 0.10]). These estimates derived from inverse-variance weighting were robust when using different MR methods. Our results suggest that elevated FI was a strong causal factor of high TGs and low HDL-C, which in turn would further increase FI. Therefore, early control of insulin resistance is critical to reduce the risk of type 2 diabetes, dyslipidemia, and cardiovascular complications.

Background and aims: Mitochondrial dysfunction is associated with increased reactive oxygen species (ROS) that are thought to drive disease risk, including stroke. We investigated the association between mtDNA abundance, as a proxy measure of mitochondrial function, and incident stroke, using multivariable-adjusted survival and Mendelian Randomization (MR) analyses. Methods: Cox-proportional hazard model analyses were conducted to assess the association between mtDNA abundance, and incident ischemic and hemorrhagic stroke over a maximum of 14-year follow-up in European -ancestry participants from UK Biobank. MR was conducted using independent (R-2 < 0.001) lead variants for mtDNA abundance (p < 5 x 10(-8)) as instrumental variables. Single-nucleotide polymorphism (SNP)-ischemic stroke associations were derived from three published open source European-ancestry results databases (cases/ controls): MEGASTROKE (60,341/454,450), UK Biobank (2404/368,771) and FinnGen (10,551/202,223). MR was performed per study, and results were subsequently meta-analyzed. Results: In total, 288,572 unrelated participants (46% men) with mean (SD) age of 57 (8) years were included in the Cox-proportional hazard analyses. After correction for considered confounders (BMI, hypertension, cholesterol, T2D), no association was found between low versus high mtDNA abundance and ischemic (HR: 1.06 [95% CI: 0.95, 1.18]) or hemorrhagic (HR: 0.97 [95% CI: 0.82, 1.15]) stroke. However, in the MR analyses after removal of platelet count-associated SNPs, we found evidence for an association between genetically-influenced mtDNA abundance and ischemic stroke (odds ratio, 1.17; confidence interval, 1.03, 1.32). Conclusions: Although the results from both multivariable-adjusted prospective and basis MR analyses did not show an association between low mtDNA and increased risk of ischemic stroke, in-depth MR sensitivity analyses may suggest evidence for a causal relationship.

Etiologic associations between some modifiable factors (metabolic risk factors and lifestyle behaviors) and cardiovascular disease (CVD) remain unclear. To identify targets for CVD prevention, we evaluated the causal associations of these factors with coronary artery disease (CAD) and ischemic stroke using a two-sample Mendelian randomization (MR) method.Previously published genome-wide association studies (GWASs) for blood pressure (BP), glucose, lipids, overweight, smoking, alcohol intake, sedentariness, and education were used to identify instruments for 15 modifiable factors. We extracted effects of the genetic variants used as instruments for the exposures on coronary artery disease (CAD) and ischemic stroke from large GWASs (N = 60 801 cases/123 504 controls for CAD and N = 40 585 cases/406 111 controls for ischemic stroke). Genetically predicted hypertension (CAD: OR, 5.19 [95% CI, 4.21-6.41]; ischemic stroke: OR, 4.92 [4.12-5.86]), systolic BP (CAD: OR, 1.03 [1.03-1.04]; ischemic stroke: OR, 1.03 [1.03-1.03]), diastolic BP (CAD: OR, 1.05 [1.05-1.06]; ischemic stroke: OR, 1.05 [1.04-1.05]), type 2 diabetes (CAD: OR, 1.11 [1.08-1.15]; ischemic stroke: OR, 1.07 [1.04-1.10]), smoking initiation (CAD: OR, 1.26 [1.18-1.35]; ischemic stroke: OR, 1.24 [1.16-1.33]), educational attainment (CAD: OR, 0.62 [0.58-0.66]; ischemic stroke: OR, 0.68 [0.63-0.72]), low-density lipoprotein cholesterol (CAD: OR, 1.55 [1.41-1.71]), high-density lipoprotein cholesterol (CAD: OR, 0.82 [0.74-0.91]), triglycerides (CAD: OR, 1.29 [1.14-1.45]), body mass index (CAD: OR, 1.25 [1.19-1.32]), and alcohol dependence (OR, 1.04 [1.03-1.06]) were causally related to CVD.This systematic MR study identified 11 modifiable factors as causal risk factors for CVD, indicating that these factors are important targets for preventing CVD.

Lipid-lowering therapy with statins and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition are effective strategies in reducing cardiovascular disease risk; however, concerns remain about potential long-term adverse neurocognitive effects.This genetics-based study aimed to evaluate the relationships of long-term PCSK9 inhibition and statin use on neurocognitive outcomes.We extracted single-nucleotide polymorphisms in 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) and PCSK9 from predominantly European ancestry-based genome-wide association studies summary-level statistics of low-density lipoprotein cholesterol and performed drug-target Mendelian randomization, proxying the potential neurocognitive impact of drug-based PCSK9 and HMGCR inhibition using a range of outcomes to capture the complex facets of cognition and dementia.Using data from a combined sample of ∼740,000 participants, we observed a neutral cognitive profile related to genetic PCSK9 inhibition, with no significant effects on cognitive performance, memory performance, or cortical surface area. Conversely, we observed several adverse associations for HMGCR inhibition with lowered cognitive performance (beta: -0.082; 95% CI: -0.16 to -0.0080; P = 0.03), reaction time (beta = 0.00064; 95% CI: 0.00030-0.00098; P = 0.0002), and cortical surface area (beta = -0.18; 95% CI: -0.35 to -0.014; P = 0.03). Neither PCSK9 nor HMGCR inhibition impacted biomarkers of Alzheimer's disease progression or Lewy body dementia risk. Consistency of findings across Mendelian randomization methods accommodating different assumptions about genetic pleiotropy strengthens causal inference.Using a wide range of cognitive function and dementia endpoints, we failed to find genetic evidence of an adverse PCSK9-related impact, suggesting a neutral cognitive profile. In contrast, we observed adverse neurocognitive effects related to HMGCR inhibition, which may well be outweighed by the cardiovascular benefits of statin use, but nonetheless may warrant pharmacovigilance.

To summarize the associations between potential causal factors and colorectal cancer (CRC) risk based on existing Mendelian randomization studies.This systematic review and meta-analysis involved a literature search in Embase and Medline. All published articles using Mendelian randomization to explore potential causal factors of CRC were included. Studies that reported Mendelian randomization estimates of standard deviation changes in exposures were included in the meta-analysis. Subgroup analyses based on sex and anatomical sites were performed.One hundred and ninety studies presented in 51 articles were included in systematic review, and 114 studies conducted in 32 articles were included in the meta-analysis. Adult body mass index, waist circumference, waist hip ratio, body height, body fat percentage, arm fat ratio, childhood obesity, lifetime cigarette consumption, short sleep, coffee consumption, and blood levels of vitamin BMost obesity-related anthropometric characteristics, several unhealthy lifestyles, and blood levels of some micronutrients, fatty acids, and diabetes-related biomarkers were positively associated with CRC risk. In contrast, some lifestyles and blood levels of some fatty acids and inflammatory biomarkers were inversely associated with CRC risk. Future studies with more valid genetic variants are needed for factors with discrepancies between Mendelian randomization and epidemiological studies.

usc Background: higher vitamin D status has been suggested to have beneficial effects on the brain. Objectives: to investigate the association between 25-hydroxyvitamin D [25(OH)D], neuroimaging features, and the risk of dementia and stroke. Methods: we used prospective data from the UK Biobank (37–73 y at baseline) to examine the association between 25(OH)D concentrations with neuroimaging outcomes (N = 33,523) and the risk of dementia and stroke (N = 427,690; 3414 and 5339 incident cases, respectively). Observational analyses were adjusted for age, sex, ethnicity, month, center, and socioeconomic, lifestyle, sun behavior, and illness-related factors. Nonlinear Mendelian randomization (MR) analyses were used to test for underlying causality for neuroimaging outcomes (N = 23,901) and dementia and stroke (N = 294,514; 2399 and 3760 cases, respectively). Result: associations between 25(OH)D and total, gray matter, white matter, and hippocampal volumes were nonlinear, with lower volumes both for low and high concentrations (adjusted P-nonlinear ≤ 0.04). 25(OH)D had an inverse association with white matter hyperintensity volume [per 10 nmol/L 25(OH)D; adjusted β: –6.1; 95% CI: –11.5, –7.0]. Vitamin D deficiency was associated with an increased risk of dementia and stroke, with the strongest associations for those with 25(OH)D

The aim of this article is to scan and analyze the genetic correlation between plasma proteome and deep venous thrombosis (DVT), and to explore the correlation between plasma protein and DVT.GWAS data of DVT and plasma proteins were analyzed with linkage disequilibrium scores, and plasma proteins that were genetically associated with DVT were screened out. To ascertain the causal link between potential plasma proteins and DVT, a Mendelian randomized (MR) study was used. This study used STRING to examine the pathogenesis of DVT in connection with the gene encoding plasma protein.Several suggestive plasma proteins were detected for DVT, such as Complement factor B (P value=0.0177), Chromogranin-A (P value=0.0158). Through MR analysis, we found that there was a significant positive causal relationship between Chromogranin-A (exposure) and DVT(outcome) (β=-0.0117, P0.0001). Our STRING analysis revealed that hsa04610 was associated with coagulation cascade in the KEGG pathway of Complement factor B(P0.0001), which was based on GO and KEGG analysis of 8 selected plasma proteins.A genetic link between plasma protein and DVT was thoroughly investigated. Our findings provide a fresh perspective on the genetics and pathogenesis of DVT.

Aims The potential effect of alcohol consumption on coronary heart disease (CHD) remains unclear. We used the variant rs671 in the aldehyde dehydrogenase 2 gene (ALDH2) as an instrument to investigate the causal role of alcohol intake in subclinical and clinical CHD. Methods We conducted two Mendelian randomization studies: a cross-sectional study of coronary artery calcification (CAC) on computed tomography of 1029 healthy men (mean age, 63.8 years) and a case–control study of 421 men with CHD [acute coronary syndrome (ACS) or stable angina pectoris] who underwent coronary revascularization and 842 age-matched male controls. Results In the CAC study, medians (25%tiles, 75%tiles) of alcohol consumption by ALDH2-rs671 *2 homozygotes [n = 86 (8.4%)], *1*2 heterozygotes [n = 397 (38.5%)], and *1 homozygotes [n = 546 (53.1%)] were 0.0 (0.0, 0.0), 28.0 (0.0, 129.0), and 224.0 (84.0, 350.0) g/week, respectively. In age-adjusted Poisson regression with robust error variance, compared with *2 homozygotes, relative risks for prevalent CAC score >0, ≥100, and ≥300 in *1 homozygotes were 1.29 (95% confidence interval, 1.06–1.57), 1.76 (1.05–2.96), and 1.81 (0.80–4.09), respectively. In age-adjusted ordinal logistic regression for CAC distributions, we observed higher odds among *1 homozygotes [odds ratio, 2.19 (1.39–3.46)] and even among *1*2 heterozygotes [1.77 (1.11–2.82)] compared with *2 homozygotes. In the case–control study, conditional logistic regression revealed lower prevalence of *1 homozygotes among men with CHD [odds ratio, 0.54 (0.35–0.82)], especially ACS [0.46 (0.27–0.77)], than controls. Conclusion Our findings indicate a positive association of alcohol consumption with CAC burden but an inverse association with clinical CHD, especially ACS.

Changes in serum inflammatory factors occur throughout the onset and multiple myeloma (MM) progression, the feedback loops make it harder to distinguish between causes and effects. In the present study, we performed a bidirectional summary-level Mendelian randomization (MR) analysis to elucidate the causal relationships of C-reactive protein (CRP) and inflammatory regulators with MM. Summary-level data of genetic variants associated with inflammation were extracted from two genome-wide association studies (GWASs) on CRP and human cytokines, while data on MM was from large meta-analyses of GWASs among 372 617 UK Biobank participants. The inverse-variance weighted (IVW) method was used as the primary MR analysis and MR-Egger, weighted median, and MR-pleiotropy residual sum and outlier (MR-PRESSO) were used as the sensitivity analyses. Our results suggested that higher levels of monocyte-specific chemokine-3 (IVW estimate odds ratio [OR

Although many studies have indicated that Psoriasis (PsO) could contribute to the risk of lung cancer, no study has reported a clear causal association between them. Our aim was to explore the potential causal association between PsO and the lung cancer risk using Mendelian randomization (MR) design.To explore a causal association between the PsO and lung cancer, we used large-scale genetic summary data from genome-wide association study (GWAS), including PsO (n = 337 159) and lung cancer (n = 361 586), based on previous observational studies. Our main analyses were conducted by inverse-variance weighted (IVW) method with random-effects model, with a complementary with the other two analyses: weighted median method and MR-Egger approach.The results of IVW methods demonstrated that genetically predicted PsO was significantly associated with higher odds of lung cancer, with an odds ratio (OR) of 1.06 (95%CI, 1.01-1.12; P = 0.02). Weighted median method and MR-Egger regression also demonstrated directionally similar results (All P 0.05). In addition, both funnel plots and MR-Egger intercepts indicated no directional pleiotropic effects between PsO and lung cancer.Our study provided potential evidence between genetically predicted PsO and lung cancer, which suggested that enhanced screening for lung cancer allows early detection of lung cancer.