Long sleep duration in elders without dementia increases risk of dementia mortality (NEDICES)

Abstract

Objective: To determine in a population-based study whether long sleep duration was associated with increased risk of dementia mortality. Methods:In this prospective, population-based study of 3,857 people without dementia aged 65 years and older (NEDICES [Neurological Disorders in Central Spain]), participants reported their daily sleep duration. The average daily total sleep duration was grouped into 3 categories: #5 hours (short sleepers), 6-8 hours (reference category), and $9 hours (long sleepers). Communitydwelling elders were followed for a median of 12.5 years, after which the death certificates of those who died were examined.Results: A total of 1,822 (47.2%) of 3,857 participants died, including 201 (11.0%) deaths among short sleepers, 832 (45.7%) among long sleepers, and 789 (43.3%) among those participants in the reference category. Of 1,822 deceased participants, 92 (5.1%) had a dementia condition reported on the death certificate (49 [53.3%] were long sleepers, 36 [39.1%] reported sleeping between 6 and 8 hours, and 7 [7.6%] were short sleepers). In an unadjusted Cox model, risk of dementia-specific mortality was increased in long sleepers (hazard ratio for dementia mortality in long sleepers 5 1.58, p 5 0.04) when compared with the reference group. In a Cox model that adjusted for numerous demographic factors and comorbidities, the hazard ratio for dementia mortality in long sleepers was 1.63 (p 5 0.03).Conclusions: Self-reported long sleep duration was associated with 58% increased risk of dementia-specific mortality in this cohort of elders without dementia. Future studies are required to confirm these findings.

Sleep Duration and Neurocognitive Function in the Hispanic Community Health Study/Study of Latinos

“…25 In contrast, HCHS/ SOL participants with longer sleep durations had markedly lower neurocognitive scores, consistent with evidence from cross-sectional and longitudinal studies suggesting that long sleep predicts impaired neurocognitive function and dementia in older adults. 4,[6][7][8] In our study, the association between sleep duration and neurocognitive function was seen across all cognitive tests, except for delayed memory. In a cohort of older men, disturbed sleep was associated primarily with decline in executive function, but not with global cognition.…”

“…[4][5][6] In addition, most studies have not accounted for daytime sleepiness, use of sleep medication, and sleep apnea, which are possible confounders between sleep duration and neurocognitive function. 7,8 Hispanic/Latinos have a 1.5 increased risk of dementia Significance Latinos, the largest US ethnic/racial minority, have a 1.5 increased risk of Alzheimer disease and related dementias (ADRD), when compared to Whites. We performed a cross-sectional evaluation of sleep duration and neurocognitive function in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), the largest study of Latinos in the U.S. We found curvilinear (inverted U-shaped) associations between sleep duration and neurocognitive function.…”

“…Sleep duration has a U-shaped association with adverse health outcome 7,8,18 ; therefore, we tested the hypothesis that sleep duration has a nonlinear, inverted U-shaped association with neurocognitive function, in the largest study of Hispanic/ Latino adults in the U.S.…”

“…Different from previous studies, 7,8 we controlled for important sleep confounders such as daytime sleepiness, use of sleep medications and excluded participants with sleep apnea by home sleep testing. However, we did not adjust for shift-work, daytime napping, and number of household members.…”

Sleep disturbances and cognitive decline in the Northern Manhattan Study

“…30 In a different cohort, long sleepers were more likely to have dementia (hazard ratio 2.2; 95% confidence interval 1.1-4.4) after 3 years of follow-up, 31 and a 58% greater risk of dementia-specific mortality up to 13 years after baseline evaluation. 32 In our study, the findings between sleep disturbances and cognition, compared to others, may be partly explained by the use of sensitive neuropsychological tests. Some other studies measured global cognition using the Mini-Mental State Examination score, which may be insensitive to cognitive variability and could explain the null findings observed in other studies.…”