Longitudinal association of apolipoprotein E and sleep with incident dementia

Introduction Few longitudinal studies have explored the association between apolipoprotein E gene (APOE) status, sleep disturbances, and incident dementia among middle-aged participants. Methods Cox regression analyses explored the association of sleep duration, insomnia, and daytime napping with incident all-cause dementia and their interaction with APOE genetic risk among 397,777 middle-aged adults. Results During a median of 10.8 years follow-up, sleeping more or fewer than 7 hours was associated with a higher dementia risk (hazard ratio [HR] for 5 vs 7 hours: 1.35, 95% confidence interval [CI] 1.11-1.64; HR for 9 vs 7 hours: 1.59; 95% CI 1.37-1.85) as was daytime napping (HR for often/all of the time vs never/rarely: 1.67; 95% CI 1.37-2.03). Stratified analyses revealed that the effects of sleep disturbances were similar across all APOE genetic risk groups. Discussion Short and long sleep duration and daytime napping in middle-aged individuals are associated with the development of dementia in later life. Sleep duration and quality are important for everyone regardless of their genetic risk by APOE genotype.