Does sleeping less cause Alzheimer's disease?
Using a bi-directional Mendelian randomisation design, we found evidence supporting a potential causal influence of genetically high risk for Alzheimer's disease on sleep disturbances, but not the other way round.
Aging populations across the world have led to an increasing prevalence of both Alzheimer disease (AD) and depression. The comorbidity of depressive disorders and late-life neurodegenerative diseases, including AD, has been widely reported. However, it is not known if any causal relationship exists between them or, alternatively, whether their co-occurrence is due to confounding or common risk factors such as aging and other lifestyle behaviours. Sleep habits are important aspects of lifestyle, and abnormal sleep patterns are among the clinical signs and symptoms of both depression and AD. However, causal relationships between sleep habits and MDD or AD have not been explored directly at a population level.
We hypothesized that sleep causally affects major depressive disorder (MDD) and AD but that there is no causal relationship between MDD and AD. To test these hypotheses, we investigated causal relationships in the triad of sleep, MDD, and AD using Mendelian randomization (MR) analyses, a causal analysis framework in modern epidemiological research.
We found evidence supporting a potential causal influence of AD on sleep disturbances. However, we did not find evidence supporting a causal role of disturbed sleep patterns on AD, suggesting that observed associations between sleep disorders and AD may be due to reverse causation. Neither did we find causal relationships between sleep-related phenotypes and MDD or between MDD and AD.
For more details, see Huang J, et al. Sleep, major depressive disorder, and Alzheimer disease: A Mendelian randomization study. Neurology. 2020.
Press Release: Is risk of Alzheimer’s linked to specific sleep patterns?