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Background: Although there is evidence of shared dysregulated pathways between diabetes and Parkinson's disease, epidemiologic research on an association between the two diseases has produced inconsistent results. Objective: We aimed to assess whether known metabolomic markers of insulin resistance and diabetes are also associated with Parkinson's disease development. Methods: We conducted a nested case-control study among Nurses' Health Study and Health Professionals Follow-up Study participants who had provided blood samples up to twenty years prior to Parkinson's diagnosis. Cases were matched to risk-set sampled controls by age, sex, fasting status, and time of blood collection. Participants provided covariate information via regularly collected cohort questionnaires. We used conditional logistic regression models to assess whether plasma levels of branched chain amino acids, acylcarnitines, glutamate, or glutamine were associated with incident development of Parkinson's disease. Results: A total of 349 case-control pairs were included in this analysis. In the primary analyses, none of the metabolites of interest were associated with Parkinson's disease development. In investigations of the association between each metabolite and Parkinson's disease at different time intervals prior to diagnosis, some metabolites showed marginally significant association but, after correction for multiple testing, only C18 : 2 acylcarnitine was significantly associated with Parkinson's disease among subjects for whom blood was collected less than 60 months prior to case diagnosis. Conclusions: Plasma levels of diabetes-related metabolites did not contribute to predict risk of Parkinson's disease. Further investigation of the relationship between pre-diagnostic levels of diabetes-related metabolites and Parkinson's disease in other populations is needed to confirm these findings. [ABSTRACT FROM AUTHOR]

• Smoking is a well-established risk factor for multiple sclerosis. • Smoking was not associated with multiple sclerosis risk in black people. • This may suggest that the association between smoking and MS varies by race/ethnicity. Smoking is a well-established risk factor for MS; however, it is not known whether its effect on disease risk varies by race/ethnicity. We conducted a nested case-control study among US military personnel who have serum samples stored at the Department of Defense Serum Repository. We measured serum cotinine levels, a marker of tobacco smoke exposure, in 157 Black and 23 White individuals who developed MS during follow-up. Controls were randomly selected and matched to each case by age, sex, race/ethnicity, dates of sample collection, and branch of military service. Smoking was not associated with an increased risk of MS in Black people (RR: 1.08, 95 % CI: 0.63–1.85). The results remained similar in analyses restricted to smoking status at baseline, to samples collected 5 years before symptom onset, and using different cut-off levels in cotinine to define smoking status. Smoking was not statistically significantly associated with MS risk in White people, but the point estimate was similar to what has previously been reported in other studies (RR: 1.85, 95 % CI: 0.56–6.16). Smoking was not associated with MS risk in Black people. Given the consistent association between smoking and MS risk in predominantly White populations, this may suggest that the association between smoking and MS varies by race/ethnicity. [ABSTRACT FROM AUTHOR]

Background: Lower levels of sun exposure in childhood have been suggested to be associated with increased risk of multiple sclerosis (MS). In this paper we extend previous work, using two novel analytical strategies.Methods: Data collected in the Environmental risk factors In MS (EnvIMS) study, a case-control study with MS cases and population-based controls from Canada, Italy and Norway, were used. Participants reported on sun exposure behaviours for 5-year age intervals from birth; we focused on the first three age intervals (≤15 years). We compared two life course epidemiology conceptual models, the critical period and the accumulation model. We also used latent class analysis to estimate MS risk for different latent sun exposure behaviour groups.Results: The analyses included 2251 cases and 4028 controls. The accumulation model was found to be the best model, which demonstrated a nearly 50% increased risk of MS comparing lowest reported summer sun exposure with highest [risk ratio (RR) = 1.47 (1.24, 1.74)]. The latent sun exposure behaviour group, characterized by low sun exposure during summer and winter and high sun protection use, had the highest risk of MS; a 76% increased risk as compared with the group with high sun exposure and low sun protection use [RR = 1.76 (1.27, 2.46)].Conclusions: Our analyses provide novel insights into the link between sun exposure and MS. We demonstrate that more time indoors during childhood and early adolescence is linked with MS risk, and that sun protection behaviours in those who spend most time indoors may play a key role in increasing risk. [ABSTRACT FROM AUTHOR]

Objective: To prospectively examine for the first time the association between plasma urate levels measured in healthy participants and future amyotrophic lateral sclerosis (ALS) risk. Methods: A pooled case-control study nested in five US prospective cohorts comprising 319,617 participants who provided blood, of which 275 had ALS during follow-up. Pre-diagnostic plasma urate was determined for all participants using a clinical colorimetric enzyme assay. Gender-specific multivariable-adjusted rate ratios (RR) of ALS incidence or death estimated by conditional logistic regression and pooled using inverse-variance weighting. Results: In age- and matching factor-adjusted analyses, a 1 mg/dL increase in urate concentration was associated with RR = 0.88 (95% CI: [0.78, 0.997] p = 0.044). After adjustment for BMI, a strong predictor of ALS and urate levels, and other potential covariates, the RR = 0.89 (95% CI: [0.78, 1.02]; p = 0.08 for 1mg/dL increase in urate). Conclusion: Elevation of plasma urate was modestly inversely associated with the risk of ALS and warrants further study for a potential role in this disease. [ABSTRACT FROM AUTHOR]

The apparently paradoxical association of tobacco use with a lower risk of Parkinson's disease (PD) is well-established [[1]], although whether nicotine or other tobacco constituents reduce the risk of PD remains uncertain. Self-reported tobacco smoking and alcohol intake were independently associated with lower PD risk in both men and women - that is, the combination of smoking and alcohol consumption was associated with a lower PD risk than either factor alone. This is a particular challenge for PD, both because some individuals identified as having PD in this study may have been a false positive, but most importantly, because there can be a considerable time interval between the first motor symptoms and the final PD diagnosis. [Extracted from the article]

Background Results from studies on diabetes and migraine risk are conflicting, which may be due to methodological limitations. Prospective studies with long follow-up could increase our understanding of the relationship between the two diseases. Method We performed a cohort study including the whole Norwegian population alive on 01.01.2004, using prescriptions registered in the Norwegian prescription database to identify individuals developing type 1 diabetes, type 2 diabetes and migraine during follow-up (10 years). We used Cox proportional hazards regression to estimate rate ratios with corresponding 95% confidence intervals for the effect of diabetes on migraine risk, adjusting for age, sex, and educational level. Result We identified 7,883 type 1 diabetes patients and 93,600 type 2 patients during the study period. Type 1 diabetes was significantly associated with a subsequent decreased migraine risk during follow-up in the age- and sex-adjusted analyses (0.74; 0.61-0.89). Type 2 diabetes was also associated with a significantly lower migraine risk (0.89; 0.83-0.95). Further adjustment for educational level yielded similar results for both diabetes. Conclusion Both type 1 and type 2 diabetes were significantly associated with a decreased risk of migraine. This suggests that diabetes or diabetes treatment may have a protective effect on the development of migraine. [ABSTRACT FROM AUTHOR]