More evidence has emerged linking sleep deficiency, dementia, and mortality.
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“Sleep disturbance and insufficiency have been shown to be associated with both the development and progression of Alzheimer’s disease and with all-cause mortality,” wrote Rebecca S. Robbins, PhD, of Brigham and Women’s Hospital, Boston, and colleagues. However, research on this topic has yielded conflicting results, and “few studies have included a comprehensive set of sleep characteristics in a single examination of incident dementia and all-cause mortality.”
In a study published in Aging, the researchers identified 2,812 adults aged 65 years and older from the National Health and Aging Trends Study (NHATS), a nationally representative longitudinal study of Medicare beneficiaries aged 65 years and older in the United States.
Participants completed surveys about sleep disturbance and duration in 2013 (1,575 individuals) and in 2014 (1,237 individuals), and the researchers examined the relationship between sleep disturbance and deficiency and incident dementia and all-cause mortality over the next 5 years. The average age of the study participants was 76.9 years, 60% were women, and 72% were White.
Overall, approximately 60% of the participants reported never or rarely having problems with alertness, approximately half said that they rarely or never napped, and more than half said they fell asleep in 15 minutes or less. Approximately 70% rated their sleep quality as good or very good, and more than 90% said they rarely or never snored.
The researchers examined the relationships between sleep characteristics and the development of incident dementia over 5 years. In a fully adjusted Cox multivariate analysis, individuals who slept 5 hours or less per night had approximately twice the risk for incident dementia as those who slept longer (hazard ratio, 2.04); risk of dementia also was higher among those who took 30 minutes or longer to fall asleep (HR, 1.45).
In addition, the risk of all-cause mortality was significantly higher among individuals who reported difficulty maintaining alertness some days or most days/every day (HR, 1.49 and HR, 1.65, respectively), routinely napping some days or most days/every day (HR, 1.38 and HR, 1.73, respectively), poor or very poor sleep quality (HR, 1.75), and sleeping 5 hours or less each night (HR, 2.38).
The study findings were limited by several factors including a population representing only one-quarter of the NHATS cohort, which prevented nationally representative estimates, the availability of only 2 years of sleep data, and small sample size for certain response categories, the researchers noted.
However, “our study offers a contribution to the literature on sleep among aging populations in its assessment of incident dementia and all-cause mortality and a range of sleep characteristics among older adults,” they said. In particular, “short sleep duration was a strong predictor of both incident dementia and all-cause mortality, suggesting this may be a sleep characteristic that is important – over and above the other predictors – of adverse outcomes among older adults,” and future areas for research include the development of novel behavioral interventions to improve sleep in this population.
The study was supported in part by the National Institute for Occupational Safety and Health; the National Heart, Lung, and Blood Institute; the National Institute on Aging; and the Brigham Research Institute Fund to Sustain Research Excellence. Lead author Dr. Robbins disclosed fees from Denihan Hospitality, Rituals Cosmetics, Dagmejan, Asystem, and SleepCycle. Several coauthors disclosed relationships with multiple pharmaceutical companies, and support from various philanthropic organizations.