Sleep, major depressive disorder and Alzheimer’s disease: a Mendelian randomisation study

Objective To explore the causal relationships between sleep, major depressive disorder (MDD), and Alzheimer’s disease (AD). Methods We conducted bi-directional two-sample Mendelian randomisation analyses. Genetic associations were obtained from the largest genome-wide association studies currently available in UK Biobank (N=446,118), the Psychiatric Genomics Consortium (N=18,759), and the International Genomics of Alzheimer’s Project (N=63,926). We used the inverse variance weighted Mendelian randomisation method to estimate the causal effects, and the weighted median and MR-Egger for sensitivity analyses to test for pleiotropic effects. Results We found that higher risk of AD was significantly associated with being a “morning person” (odds ratio (OR)=1.01, P=0.001), shorter sleep duration (self-reported: β=-0.006, P=1.9×10-4; accelerometer-based: β=-0.015, P=6.9×10-5), less likely to report long sleep (β=-0.003, P=7.3×10-7), earlier timing of the least active 5 hours ...