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Background:This randomised phase II trial compared dose-escalated weekly paclitaxel (wPTX) vs standard-dose wPTX for patients with previously treated advanced gastric cancer (AGC).Methods:Ninety patients were randomised to a standard dose of wPTX (80 mg m−2) or an escalated dose of wPTX (80-120 mg m−2) to assess the superiority of overall survival (OS) with a one-sided alpha error of 0.3 and a power of 0.8.Results:The median OS showed a trend towards longer survival in the dose-escalated arm (11.8 vs 9.6 months; hazard ratio (HR), 0.75; one-sided P=0.12), although it was statistically not significant. The median progression-free survival (PFS) was significantly longer in the dose-escalated arm (4.3 vs 2.5 months, HR, 0.55; P=0.017). Objective response rate was 30.3% with dose escalation and 17.1% with standard dose (P=0.2). The frequency of all grades of neutropenia was significantly higher with dose escalation (88.7% vs 60.0%, P=0.002); however, no significant difference was observed in the proportion of patients experiencing grade 3 or more (40.9% vs 31.1%, P=0.34).Conclusion:Dose-escalated wPTX in patients with pretreated AGC met our predefined threshold of primary end point, OS (P<0.3); however, it did not show a significantly longer OS. Progression-free survival was significantly better with dose escalation. [ABSTRACT FROM AUTHOR]

The association between smoking status and survival in oral cavity squamous cell carcinoma (OSCC) patients remains unclear. Therefore, we evaluated the association between smoking status before treatment and clinical outcome in OSCC patients. We conducted a retrospective cohort study of 222 OSCC patients who were treated at Aichi Cancer Center in Japan. Of these, 82 patients (36.9%) were non-smokers, 65 (29.3%) were light smokers (pack-years smoking (PY) <30), 54 (24.3%) were moderate smokers (30PY<60), and 21 (9.5%) were heavy smokers (60PY). The survival impact of pre-treatment smoking status was evaluated using multivariate proportional hazard models. Five-year overall survival for non-, light, moderate, and heavy smokers was 72.9% (95% confidence interval CI): (61.4-81.5), 85.5% (74.0-92.2), 59.9% (44.3-72.4) and 69.0% (42.8-85.0). Adjusted hazard ratios (HRs) for moderate and heavy smokers in comparison with light smokers were 2.44 (1.07-5.57, P=0.034) and 2.66 (0.97-7.33, P=0.058) and the dose-response relationship among smokers was statistically significance (P(trend)=0.024). In addition, adjusted HR for non-smokers relative to light smokers was 2.27 (0.84-6.15, P=0.108). We observed a suggestive heterogeneity in the impact of smoking status by treatment method (P for heterogeneity=0.069). Effect of smoking was evident only among the chemoradiotherapy or radiotherapy group. In this study, we found the significant positive dose-response relationship among smokers on clinical outcome in OSCC patients and that non-smokers were worse prognosis than light smokers. In addition, this effect might differ by treatment method. [ABSTRACT FROM AUTHOR]

Background: Reproductive factors, such as age at menarche, are known to be associated with disease risk, but data on trends in these factors in Japan are limited. In this study, we investigated secular trends in reproductive factors and explored their potential association with socioeconomic and historical events., Methods: We conducted a retrospective analysis of 62,005 Japanese women born between 1890 and 1991 using a survey conducted over 25 years. Trends in reproductive factors were analyzed using linear and joinpoint regression models, and their associations with major historical events involving Japan were evaluated., Results: We found that the age at menarche showed a significant downward trend (P < 0.001) over the century. Three joinpoints were identified, in 1932 (15.23 years old), 1946 (13.48 years old), and 1959 (12.71 years old), which indicated that average age at menarche decreased by approximately 0.8% per year between 1932 and 1946, and then by 0.4% per year between 1946 and 1959, both of which were statistically significant. However, after 1959, age of menarche remained stable. Analyses of other reproductive factors found significant changes, including a decrease in parity and the number of babies breastfed, and an increase in age at first birth., Conclusion: Age at menarche showed a long-term downward trend in Japan, with significant change points in annual percent change. Other factors showed secular changes in trends as well. These change points were observed at the same time as historical events, namely wars and economic development, suggesting that socioeconomic and environmental changes at the population level affect reproductive factors in females.

Background: The family history of gastric cancer holds important implications for cancer surveillance and prevention, yet existing evidence predominantly comes from case-control studies. We aimed to investigate the association between family history of gastric cancer and gastric cancer risk overall and by various subtypes in Asians in a prospective study., Methods: We included 12 prospective cohorts with 550,508 participants in the Asia Cohort Consortium. Cox proportional hazard regression was used to estimate study-specific adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between family history of gastric cancer and gastric cancer incidence and mortality, then pooled using random-effects meta-analyses. Stratified analyses were performed for the anatomical subsites and histological subtypes., Results: During the mean follow-up of 15.6 years, 2258 incident gastric cancers and 5194 gastric cancer deaths occurred. The risk of incident gastric cancer was higher in individuals with a family history of gastric cancer (HR 1.44, 95% CI 1.32-1.58), similarly in males (1.44, 1.31-1.59) and females (1.45, 1.23-1.70). Family history of gastric cancer was associated with both cardia (HR 1.26, 95% CI 1.00-1.60) and non-cardia subsites (1.49, 1.35-1.65), and with intestinal- (1.48, 1.30-1.70) and diffuse-type (1.59, 1.35-1.87) gastric cancer incidence. Positive associations were also found for gastric cancer mortality (HR 1.30, 95% CI 1.19-1.41)., Conclusions: In this largest prospective study to date on family history and gastric cancer, a familial background of gastric cancer increased the risk of gastric cancer in the Asian population. Targeted education, screening, and intervention in these high-risk groups may reduce the burden of gastric cancer., (© 2024. The Author(s).)

Background: Improving diets requires an awareness of the need to limit foods for which excessive consumption is a health problem. Since there are limited reports on the link between this awareness and mortality risk, we examined the association between awareness of limiting food intake (energy, fat, and sweets) and all-cause mortality in a Japanese cohort study., Methods: Participants comprised 58,772 residents (27,294 men; 31,478 women) aged 35-69 years who completed baseline surveys of the Japan Multi-Institutional Collaborative Cohort Study from 2004 to 2014. Hazard ratios (HRs) for all-cause mortality and 95% confidence intervals (CIs) were estimated by sex using a Cox proportional hazard model, with adjustment for related factors. Mediation analysis with fat intake as a mediator was also conducted., Results: The mean follow-up period was 11 years, and 2,516 people died. Estimated energy and fat intakes according to the Food Frequency Questionnaire were lower in those with awareness of limiting food intake than in those without this awareness. Women with awareness of limiting fat intake showed a significant decrease in mortality risk (HR 0.73; 95% CI, 0.55-0.94). Mediation analysis revealed that this association was due to the direct effect of the awareness of limiting fat intake and that the total effect was not mediated by actual fat intake. Awareness of limiting energy or sweets intake was not related to mortality risk reduction., Conclusion: Awareness of limiting food intake had a limited effect on reducing all-cause mortality risk.

Background: Evidence suggests a possible link between diabetes and gastric cancer risk, but the findings remain inconclusive, with limited studies in the Asian population. We aimed to assess the impact of diabetes and diabetes duration on the development of gastric cancer overall, by anatomical and histological subtypes., Methods: A pooled analysis was conducted using 12 prospective studies included in the Asia Cohort Consortium. Among 558 981 participants (median age 52), after a median follow-up of 14.9 years and 10.5 years, 8556 incident primary gastric cancers and 8058 gastric cancer deaths occurred, respectively. Cox proportional hazard regression models were used to estimate study-specific hazard ratios (HRs) and 95% confidence intervals (CIs) and pooled using random-effects meta-analyses., Results: Diabetes was associated with an increased incidence of overall gastric cancer (HR 1.15, 95% CI 1.06-1.25). The risk association did not differ significantly by sex (women vs men: HR 1.31, 95% CI 1.07-1.60 vs 1.12, 1.01-1.23), anatomical subsites (noncardia vs cardia: 1.14, 1.02-1.28 vs 1.17, 0.77-1.78) and histological subtypes (intestinal vs diffuse: 1.22, 1.02-1.46 vs 1.00, 0.62-1.61). Gastric cancer risk increased significantly during the first decade following diabetes diagnosis (HR 4.70, 95% CI 3.77-5.86), and decreased with time (nonlinear p < .01). Positive associations between diabetes and gastric cancer mortality were observed (HR 1.15, 95% CI 1.03-1.28) but attenuated after a 2-year time lag., Conclusion: Diabetes was associated with an increased gastric cancer incidence regardless of sex, anatomical subsite, or subtypes of gastric cancer. The risk of gastric cancer was particularly high during the first decade following diabetes diagnosis., (© 2024 The Authors. Journal of Diabetes published by Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd.)

There has been growing evidence suggesting that diabetes may be associated with increased liver cancer risk. However, studies conducted in Asian countries are limited. This project considered data of 968,738 adults pooled from 20 cohort studies of Asia Cohort Consortium to examine the association between baseline diabetes and liver cancer incidence and mortality. Cox proportional hazard model and competing risk approach was used for pooled data. Two-stage meta-analysis across studies was also done. There were 839,194 subjects with valid data regarding liver cancer incidence (5654 liver cancer cases [48.29/100,000 person-years]), follow-up time and baseline diabetes (44,781 with diabetes [5.3%]). There were 747,198 subjects with valid data regarding liver cancer mortality (5020 liver cancer deaths [44.03/100,000 person-years]), follow-up time and baseline diabetes (43,243 with diabetes [5.8%]). Hazard ratio (HR) (95% confidence interval [95%CI]) of liver cancer diagnosis in those with vs. without baseline diabetes was 1.97 (1.79, 2.16) (p < .0001) after adjusting for baseline age, gender, body mass index, tobacco smoking, alcohol use, and heterogeneity across studies (n = 586,072; events = 4620). Baseline diabetes was associated with increased cumulative incidence of death due to liver cancer (adjusted HR (95%CI) = 1.97 (1.79, 2.18); p < .0001) (n = 595,193; events = 4110). A two-stage meta-analytic approach showed similar results. This paper adds important population-based evidence to current literature regarding the increased incidence and mortality of liver cancer in adults with diabetes. The analysis of data pooled from 20 studies of different Asian countries and the meta-analysis across studies with large number of subjects makes the results robust., (© 2024 UICC.)

Background: The present genome-wide association study (GWAS) aimed to reveal the genetic loci associated with folate metabolites, as well as to detect related gene-environment interactions in Japanese., Methods: We conducted the GWAS of plasma homocysteine (Hcy), folic acid (FA), and vitamin B 12 (VB 12 ) levels in the Japan Multi-Institutional Collaborative Cohort (J-MICC) Study participants who joined from 2005 to 2012, and also estimated gene-environment interactions. In the replication phase, we used data from the Yakumo Study conducted in 2009. In the discovery phase, data of 2,263 participants from four independent study sites of the J-MICC Study were analyzed. In the replication phase, data of 573 participants from the Yakumo Study were analyzed., Results: For Hcy, MTHFR locus on chr 1, NOX4 on chr 11, CHMP1A on chr 16, and DPEP1 on chr 16 reached genome-wide significance (P < 5 × 10 -8 ). MTHFR also associated with FA, and FUT2 on chr 19 associated with VB 12 . We investigated gene-environment interactions in both studies and found significant interactions between MTHFR C677T and ever drinking, current drinking, and physical activity >33% on Hcy (β = 0.039, 0.038 and -0.054, P = 0.018, 0.021 and <0.001, respectively) and the interaction of MTHFR C677T with ever drinking on FA (β = 0.033, P = 0.048)., Conclusion: The present GWAS revealed the folate metabolism-associated genetic loci and gene-environment interactions with drinking and physical activity in Japanese, suggesting the possibility of future personalized cardiovascular disease prevention.

Objective: Although small fish are an important source of micronutrients, the relationship between their intake and mortality remains unclear. This study aimed to clarify the association between intake of small fish and all-cause and cause-specific mortality., Design: We used the data from a cohort study in Japan. The frequency of the intake of small fish was assessed using a validated FFQ. The hazard ratio (HR) and 95 % confidence interval (CI) for all-cause and cause-specific mortality according to the frequency of the intake of small fish by sex were estimated using a Cox proportional hazard model with adjustments for covariates., Setting: The Japan Multi-Institutional Collaborative Cohort Study., Participants: A total of 80 802 participants (34 555 males and 46 247 females), aged 35-69 years., Results: During a mean follow-up of 9·0 years, we identified 2482 deaths including 1495 cancer-related deaths. The intake of small fish was statistically significantly and inversely associated with the risk of all-cause and cancer mortality in females. The multivariable-adjusted HR (95 % CI) in females for all-cause mortality according to the intake were 0·68 (0·55, 0·85) for intakes 1-3 times/month, 0·72 (0·57, 0·90) for 1-2 times/week and 0·69 (0·54, 0·88) for ≥ 3 times/week, compared with the rare intake. The corresponding HR (95 % CI) in females for cancer mortality were 0·72 (0·54, 0·96), 0·71 (0·53, 0·96) and 0·64 (0·46, 0·89), respectively. No statistically significant association was observed in males., Conclusions: Intake of small fish may reduce the risk of all-cause and cancer mortality in Japanese females.

The relationships between the therapeutic effects of immune checkpoint inhibitors (ICIs) and the intestinal flora have attracted increasing attention. However, the effects of oral probiotics on the efficacies of ICIs used to treat non-small-cell lung cancer (NSCLC) remain unclear. We investigated the effects of probiotics on the efficacies of ICIs in patients treated with and without chemotherapy. We investigated patients with advanced NSCLC on ICI monotherapy or combination ICI and chemotherapy using the Okayama Lung Cancer Study Group Immunotherapy Database (OLCSG-ID) and the Okayama Lung Cancer Study Group Immunochemotherapy Database (OLCSG-ICD). In total, 927 patients (482 on ICI monotherapy, 445 on an ICI + chemotherapy) were enrolled. Most were male, of good performance status, smokers, and without epidermal growth factor receptor (EGFR)/anaplastic lymphoma kinase (ALK) mutations. Probiotics were administered to 19% of patients on ICI monotherapies and 17% of those on ICIs + chemotherapy. Of the former patients, progression-free survival (PFS) and overall survival (OS) were significantly better in the probiotics group (PFS 7.9 vs. 2.9 months, hazard ratio [HR] 0.54, p < .001; OS not attained vs. 13.1 months, HR 0.45, p < .001). Among patients receiving ICI and chemotherapy, there were no significant differences in PFS between those on probiotics and not but OS was significantly better in the probiotics group (PFS 8.8 vs. 8.6 months, HR 0.89, p = .43; OS not attained vs. 22.6 months, HR 0.61, p = .03). Patients on probiotics experienced better outcomes following ICI treatment., (© 2024 UICC.)

Genome-wide association studies (GWAS) have identified more than 200 common genetic variants independently associated with colorectal cancer (CRC) risk, but the causal variants and target genes are mostly unknown. We sought to fine-map all known CRC risk loci using GWAS data from 100,204 cases and 154,587 controls of East Asian and European ancestry. Our stepwise conditional analyses revealed 238 independent association signals of CRC risk, each with a set of credible causal variants (CCVs), of which 28 signals had a single CCV. Our cis-eQTL/mQTL and colocalization analyses using colorectal tissue-specific transcriptome and methylome data separately from 1299 and 321 individuals, along with functional genomic investigation, uncovered 136 putative CRC susceptibility genes, including 56 genes not previously reported. Analyses of single-cell RNA-seq data from colorectal tissues revealed 17 putative CRC susceptibility genes with distinct expression patterns in specific cell types. Analyses of whole exome sequencing data provided additional support for several target genes identified in this study as CRC susceptibility genes. Enrichment analyses of the 136 genes uncover pathways not previously linked to CRC risk. Our study substantially expanded association signals for CRC and provided additional insight into the biological mechanisms underlying CRC development., (© 2024. The Author(s).)

Background: Epidemiological studies have shown inconsistent results regarding the link between smoking and breast cancer risk, despite the biological plausibility of a positive association., Methods: Participants were 166 611 women from nine prospective cohort studies in Japan which launched in 1984-1994 and followed for 8-22 years. Information on smoking and secondhand smoke was obtained through self-administered baseline questionnaires. Breast cancer was defined as code C50 according to the International Classification of Diseases for Oncology, 3rd Edition or the International Classification of Diseases, 10th Revision. After adjusting for several potential confounders, relative risks for breast cancer were calculated in the individual studies according to the current or previous status of active and passive smoking using Cox regression, followed by a summary estimate of hazard ratios using random-effects meta-analyses., Results: Of the 60 441 participants who reported being premenopausal and 106 170 who reported being postmenopausal at baseline, 897 and 1168 developed breast cancer during follow-up, respectively. Compared with never smokers, current smokers had a higher risk of developing breast cancer before the age of 50 years. In addition, ever smokers who started smoking at 30 years of age or younger, or who started smoking before first childbirth, had a higher risk of developing breast cancer before the age of 50 years. No association between adulthood or childhood exposure to secondhand smoke and breast cancer was observed., Conclusion: Smoking may increase the risk of premenopausal breast cancer, and smoking earlier in life might be especially harmful. The impact of secondhand smoke needs further investigation., (© The Author(s) 2024; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.)

Body fatness is considered a probable risk factor for biliary tract cancer (BTC), whereas cholelithiasis is an established factor. Nevertheless, although obesity is an established risk factor for cholelithiasis, previous studies of the association of body mass index (BMI) and BTC did not take the effect of cholelithiasis fully into account. To better understand the effect of BMI on BTC, we conducted a pooled analysis using population-based cohort studies in Asians. In total, 905 530 subjects from 21 cohort studies participating in the Asia Cohort Consortium were included. BMI was categorized into four groups: underweight (<18.5 kg/m 2 ); normal (18.5-22.9 kg/m 2 ); overweight (23-24.9 kg/m 2 ); and obese (25+ kg/m 2 ). The association between BMI and BTC incidence and mortality was assessed using hazard ratios (HR) and 95% confidence intervals (CIs) by Cox regression models with shared frailty. Mediation analysis was used to decompose the association into a direct and an indirect (mediated) effect. Compared to normal BMI, high BMI was associated with BTC mortality (HR 1.19 [CI 1.02-1.38] for males, HR 1.30 [1.14-1.49] for females). Cholelithiasis had significant interaction with BMI on BTC risk. BMI was associated with BTC risk directly and through cholelithiasis in females, whereas the association was unclear in males. When cholelithiasis was present, BMI was not associated with BTC death in either males or females. BMI was associated with BTC death among females without cholelithiasis. This study suggests BMI is associated with BTC mortality in Asians. Cholelithiasis appears to contribute to the association; and moreover, obesity appears to increase BTC risk without cholelithiasis., (© 2023 UICC.)

Mounting evidence suggests that body mass index (BMI) is inversely associated with the risk of lung cancer. However, relatively few studies have explored this association in Asian people, who have a much lower prevalence of obesity than Caucasians. We pooled data from 10 prospective cohort studies involving 444,143 Japanese men and women to address the association between BMI and the risk of lung cancer. Study-specific hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated in each cohort using the Cox proportional hazards model. A meta-analysis was undertaken by combining the results from each cohort. Heterogeneity across studies was evaluated using Cochran's Q and I 2 statistics. During 5,730,013 person-years of follow-up, 6454 incident lung cancer cases (4727 men and 1727 women) were identified. Baseline BMI was inversely associated with lung cancer risk in men and women combined. While leanness (BMI <18.5) was associated with a higher risk of lung cancer (HR 1.35; 95% CI, 1.16-1.57), overweight and obesity were associated with a lower risk, with HRs of 0.77 (95% CI, 0.71-0.84) and 0.69 (95% CI, 0.45-1.07), respectively. Every 5 kg/m 2 increase in BMI was associated with a 21% lower risk of lung cancer (HR 0.79; 95% CI, 0.75-0.83; p < 0.0001). Our pooled analysis indicated that BMI is inversely associated with the risk of lung cancer in the Japanese population. This inverse association could be partly attributed to residual confounding by smoking, as it was more pronounced among male smokers., (© 2024 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)

Background: Recent trials have reported a median overall survival (OS) of 11-17 months in patients with advanced gastric cancer (AGC). However, it is unclear how recently approved drugs contribute to patient prognosis., Objectives: We aimed to evaluate the characteristics and survival in patients with AGC over the past 15 years., Design: Retrospective study., Methods: We evaluated data of 1355 patients with AGC who received first-line chemotherapy between January 2005 and March 2019 at a single institution. We compared the characteristics and survival rates across four periods: January 2005-December 2007 (period A), January 2008-February 2011 (period B), March 2011-May 2015 (period C), and June 2015-March 2019 (period D). The median follow-up duration was 13.1 months, with 312, 333, 393, and 317 patients in periods A, B, C, and D, respectively., Results: There were no significant differences in patient characteristics between the four periods, except for the proportion of patients who underwent prior gastrectomy and human epidermal growth factor receptor 2 (HER2) testing. Patients in period D had significantly longer OS than those in period A [median: 15.7 versus 12.4 months; adjusted hazard ratio (aHR): 0.79; p = 0.02]. The mean OS in patients with liver metastasis (LM) in period D was remarkably longer than that in patients in period A (median: 19.3 versus 12.4 months; aHR: 0.61; p < 0.01), while that in patients with peritoneal metastasis showed limited improvement., Conclusion: Clinical strategy changes, including gastrectomy, HER2 testing, and approval of new drugs, may be associated with improved OS in patients with AGC. In the last 4 years, a remarkable improvement has been observed in patients with LM., Competing Interests: TO reports personal fees from ONO Pharmaceutical, personal fees from BMS, personal fees from Taiho, personal fees from Daichi-Sankyo, outside the submitted work; YN reports grants and personal fees from ONO Pharmaceutical, grants and personal fees from Bristol-Mayers Squibb, grants and personal fees from AstraZeneca, grants and personal fees from Daiichi Sankyo, grants and personal fees from Yakult Honsha, personal fees from Taiho, personal fees from Eli Lilly, outside the submitted work; YM reports personal fees from MSD, personal fees from Lilly Japan, personal fees from Takeda, personal fees from Bristol Myers Squibb, personal fees from Taiho, outside the submitted work; KH reports grants from Pfizer, outside the submitted work; TM reports grants and personal fees from MSD, grants and personal fees from Amgen, grants and personal fees from ONO Pharmaceutical, grants and personal fees from Daiichi Sankyo, grants from Novartis, grants from Pfizer, personal fees from Taiho, personal fees from Bristol Myers Squibb, personal fees from Eli Lilly, personal fees from Takeda, grants from Boehringer-Ingelheim, grants from Syneos Health Clinical, personal fees from Chugai, personal fees from Nippon Kayaku, grants from Cimic Shift Zero, personal fees from Merck Bio Pharma, personal fees from Bayer, personal fees from Yakult Honsha, personal fees from Sanofi, personal fees from ONO Pharmaceutical, outside the submitted work; HT reports grants and personal fees from Takeda, grants from Daiichi Sankyo, grants and personal fees from ONO Pharmaceutical, personal fees from Eli Lilly, personal fees from Merck Biopharma, personal fees from Chugai, outside the submitted work; SK reports grants and personal fees from Eli Lilly, grants from Nobelpharma, grants and personal fees from Taiho, grants and personal fees from MSD, grants and personal fees from Bayer, grants from Yansen, grants and personal fees from Chugai, grants and personal fees from ONO Pharmaceutical, grants from Daiichi Sankyo, personal fees from Merck, personal fees from BMS, outside the submitted work; MA reports personal fees from Eisai Co., Ltd, personal fees from ONO Pharmaceutical, personal fees from Chugai Pharmaceutical Co. Ltd, personal fees from Mundipharma Co., Ltd, personal fees from Taiho Pharmaceutical Co., Ltd, outside the submitted work; SI reports grants from ONO Pharmaceutical, grants from Merck Sharp & Dohme, grants from AstraZeneca, personal fees from Taiho Pharmaceutical, personal fees from Otsuka, outside the submitted work; MT reports personal fees from Bristol Myers Squibb, outside the submitted work; KM reports grants from Chugai, grants and personal fees from MSD, grants and personal fees from Amgen, grants and personal fees from ONO Pharmaceutical, grants from Astellas, grants from Sanofi, grants from Taiho, grants from Eisai, grants and personal fees from Daiichi Sankyo, grants from Novartis, grants from Pfizer, personal fees from AstraZeneca, personal fees from Taiho, personal fees from Bristol Myers Squibb, personal fees from Eli Lilly, personal fees from Takeda, outside the submitted work; others have declared no potential conflicts of interest., (© The Author(s), 2024.)

Background: Although many observational studies have demonstrated significant relationships between obesity and cardiometabolic traits, the causality of these relationships in East Asians remains to be elucidated., Methods: We conducted individual-level Mendelian randomization (MR) analyses targeting 14,083 participants in the Japan Multi-Institutional Collaborative Cohort Study and two-sample MR analyses using summary statistics based on genome-wide association study data from 173,430 Japanese. Using 83 body mass index (BMI)-related loci, genetic risk scores (GRS) for BMI were calculated, and the effects of BMI on cardiometabolic traits were examined for individual-level MR analyses using the two-stage least squares estimator method. The β-coefficients and standard errors for the per-allele association of each single-nucleotide polymorphism as well as all outcomes, or odds ratios with 95% confidence intervals were calculated in the two-sample MR analyses., Results: In individual-level MR analyses, the GRS of BMI was not significantly associated with any cardiometabolic traits. In two-sample MR analyses, higher BMI was associated with increased risks of higher blood pressure, triglycerides, and uric acid, as well as lower high-density-lipoprotein cholesterol and eGFR. The associations of BMI with type 2 diabetes in two-sample MR analyses were inconsistent using different methods, including the directions., Conclusion: The results of this study suggest that, even among the Japanese, an East Asian population with low levels of obesity, higher BMI could be causally associated with the development of a variety of cardiometabolic traits. Causality in those associations should be clarified in future studies with larger populations, especially those of BMI with type 2 diabetes.