Apolipoprotein E Epsilon 4 (Apoe Epsilon 4) Allele Is Associated With Long Sleep Duration Among Elderly With Cognitive Impairment

Background: Apolipoprotein E gene (APOE) epsilon 4 allele increases the risk for Alzheimer's disease (AD). Furthermore, among patients with cognitive impairment, longer sleep duration is associated with worse cognitive performance. To date, literature examining the associations between APOE epsilon 4 allele and objective sleep duration is limited.Objective: Our aim was to assess the association between APOE epsilon 4 and objective sleep duration, among patients with mild cognitive impairment (MCI) and AD. A sub-sample of 89 patients with AD (n = 49) and MCI (n = 40) were recruited from a large, population-based cohort of 3,140 elders (>60 years) residing on Crete, Greece.Methods: All participants underwent medical history/physical examination, extensive neuropsychiatric and neuropsychological evaluation, 3-day 24 h actigraphy and APOE epsilon 4 allele genotyping. Comparisons of sleep duration variables between APOE epsilon 4 allele carriers and non-carriers were assessed using ANCOVA, controlling for confounders.Results: The sample included 18 APOE epsilon 4 carriers and 71 non-carriers, aged 78.6 +/- 6.6 and 78.2 +/- 6.5 years, respectively. Comparisons between the APOE epsilon 4 carriers and non-carriers revealed no significant differences in terms of demographic and clinical variables. In terms of objective sleep duration across the two groups, APOE epsilon 4 carriers compared to non-carriers had significantly longer nighttime Total Sleep Time (nTST) (7.7 +/- 1.4 versus 7.2 +/- 1.3 h, respectively, p = 0.011), as well as 24 h TST (8.5 +/- 1.6 versus 7.8 +/- 1.5 h, respectively, p = 0.012).Conclusion: Among patients with MCI and AD, APOE epsilon 4 carriers have longer objective nighttime and 24 h sleep duration compared to non-carriers. These findings further support that objective long sleep duration is a genetically-driven pre-clinical marker associated with worse prognosis in elderly with cognitive impairment.