Mendelian randomization study of coffee consumption and age at onset of Huntington's disease

Background & aim: The association between habitual coffee or caffeine consumption and age at onset (AAO) of Huntington's disease (HD) is unclear. We employed Mendelian randomization to investigate the causal relationship between coffee consumption and AAO of HD. Methods: The instrumental variable including 14 independent genetic variants associated with coffee consumption was selected from a genome-wide association study (GWAS) meta-analysis of 375,833 individuals of European ancestry. Genetic association estimates for AAO of HD were obtained from the Genetic Modifiers of Huntington's Disease Consortium GWAS meta-analysis including 9064 HD patients of European ancestry. The inverse variance weighted method was used to evaluate the causal estimate and a comprehensive set of analyses tested the robustness of our results. Results: Genetically predicted higher coffee consumption was associated with an earlier AAO of HD (β = −1.84 years, 95% confidence interval = −3.47 to −0.22, P = 0.026). Results were robust to potential pleiotropy and weak instrument bias. Conclusions: This genetic study suggests high coffee consumption is associated with an earlier AAO of HD. Coffee is widely consumed and thus our findings, if confirmed, offers a potential way to delay the onset of this debilitating autosomal dominant disease.