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

Abstract Introduction 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 y) 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 = .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. Discussion In older women, habitual sleep duration predicts the future risk for cognitive impairments including dementia, independent of vascular risk factors.