Sleep duration, cognitive decline, and dementia risk in older women

Abstract

Background Consistent evidence linking habitual sleep duration with risks of mild cognitive impairment (MCI) and dementia is lacking. Methods We conducted a prospective study on 7444 community-dwelling women (aged 65–80) with self-reported sleep duration, within the Women’s Health Initiative Memory Study in 1995–2008. Incident MCI/dementia cases were ascertained by validated protocols. Cox models were used to adjust for multiple sociodemographic and lifestyle factors, depression, cardiovascular disease (CVD), and other clinical characteristics. Results We found a statistically significant (p=0.03) V-shaped association, with a higher MCI/dementia risk in women with either short (≤6 hours/night) or long (≥8 hours/night) sleep duration (vs.7 hours/night). The multicovariate-adjusted hazard for MCI/dementia was increased by 36% in short sleepers irrespective of CVD, and by 35% in long sleepers without CVD. A similar V-shaped association was found with cognitive decline. Conclusion In older women, habitual sleep duration predicts the future risk for cognitive impairments including dementia, independent of vascular risk factors.

Longer Duration of Sleep and Risk of Cognitive Decline: A Meta-Analysis of Observational Studies

“…After reviewing the full texts of the remaining 30 articles, 20 articles were excluded because of the following reasons: not relevant to our analysis ( n = 5) [14,17,[21][22][23], insufficient data ( n = 11) [12,15,16,[24][25][26][27][28][29][30][31] , shared an identical study population with other articles ( n = 1) [19], data from preexisting dementia [32] , using dementia mortality as a result [33] , and using an acute biomarker as exposure [34] . The remaining 10 studies (3 case-control studies [10,11,35] and 7 cohort studies [36][37][38][39][40][41][42] were included in the final analysis.…”

“…Table 1 shows the general characteristics of the included studies. Seven studies [10,11,35,37,38,40,41] involved cognitive impairment, 2 studies involved dementia [36,39] , and 1 study involved both cognitive impairment and dementia [42] . The included studies were published between 2009 and 2015, spanning 6 years.…”

“…The included studies were published between 2009 and 2015, spanning 6 years. They were conducted in the following countries: Spain ( n = 3) [10,36,41] , USA ( n = 3) [11,40,42] , Germany ( n = 1) [37] , England ( n = 1) [38] , Finland ( n = 1) [39] , and China ( n = 1) [35] . All 3 casecontrol studies were population-based studies.…”

Sleep Duration and Dementia in Older Adults

“…Chen et al [2] reported the effect of sleep duration on subsequent cognitive decline, mild cognitive impairment (MCI) or dementia by a prospective study on female inhabitants, and there was a significant Vshaped association between MCI/dementia risk and shorter or longer sleep durations. Keage et al [3] also conducted a prospective study linking sleep duration and cognitive decline or dementia, and there was a significant increase in odds ratio of shorter sleep duration for cognitive decline, although stratified analysis by gender was not conducted.…”

Sleep duration and cognitive impairment in older adults

“…The authors concluded that old subjects with long sleep duration had a risk of decreased cognitive performance. I have two comments on their study.First, Chen et al [2] reported the association between self-reported sleep duration and cognitive decline or mild cognitive impairment (MCI)/dementia in older women. Although they concluded that both short and long sleep duration had a risk for cognitive decline and MCI/dementia, adjusted hazard ratio of short sleep duration against normal sleep duration for MCI/dementia only showed statistical significance.…”