APOE genotype and nonrespiratory sleep parameters in cognitively intact older adults

Study Objectives: The apolipoprotein E (APOE) ϵ4 allele increases Alzheimer's disease (AD) risk and has been linked to a greater risk of sleep-disordered breathing. We investigated the association of APOE genotype with nonrespiratory sleep parameters. Methods: We studied 1264 cognitively normal participants in the Baltimore Longitudinal Study of Aging (mean = 57.5 ± 16.1 years, range 19.9-92.0, 48.2% women, 19.8% African American) with APOE genotyping and self-reported sleep duration (≥9, 7 or 8, ≤6 hours), difficulty falling/staying asleep, and napping. We compared ϵ4 carriers with all noncarriers and compared persons at reduced (ϵ2/ϵ2 or ϵ2/ϵ3) or elevated AD risk (≥1 ϵ4 allele) with those neutral for AD risk (ϵ3/ϵ3). Results: In fully adjusted models, those with ≥1 ϵ4 allele had a greater odds of being in a shorter sleep duration category compared to all noncarriers (odds ratio [OR] = 1.41, 95% confidence interval [CI] 1.06, 1.88) and ϵ3/ϵ3 carriers (OR = 1.43, 95% CI 1.06, 1.92). Compared to ϵ3/ϵ3 carriers, ϵ2/ϵ2 or ϵ2/ϵ3 carriers had a lower odds of reporting napping (OR = 0.64, 95% CI 0.43, 0.96). Among participants aged ≥50 years, sleep duration findings remained and ϵ4 carriers had a greater odds of trouble falling/staying asleep than noncarriers (OR = 1.49, 95% CI 1.02, 2.17). We found some evidence for stronger associations of ϵ4 with sleep duration among African Americans. Conclusions: Self-reported sleep duration, napping, and trouble falling/staying asleep differ by APOE genotype. Studies are needed to examine whether APOE promotes AD by degrading sleep and to clarify the role of race in these associations.