Do sleep patterns predict older adults’ likelihood of developing dementia? Researchers attempted to answer this question by looking at how sleep patterns reported by older adults related to their incidence of dementia after 17 years of follow-up.
The 11,247 participants were at least 65 at the start of this study, when their cognitive functioning and details of their sleep patterns were assessed. Sleep characteristics collected included time spent in bed, sleep quality (difficulty falling asleep, disturbed sleep, repeated awakenings and premature awakening), how restorative the sleep was (difficulty waking and not feeling rested), bedtime, wake-up time, and heavy snoring. At the start of the study, researchers found that extended time in bed (over nine hours) was associated with poorer cognitive functioning, while both waking up later (after 9:00 a.m.) and later bedtimes were associated with better cognitive functioning.
Over the course of 17 years, 1,850 of the participants were diagnosed with dementia. When the researchers looked at how baseline sleep characteristics were associated with the likelihood of dementia, they observed both short (less than six hours) and long (greater than nine hours) times spent in bed were associated with a greater likelihood of dementia, as was waking up later. There was no association between the other factors and dementia.
When researchers took into account cognitive performance at baseline, they found that in individuals with no cognitive problems at the start of the study, both short and long time in bed still predicted higher chance of dementia. For those with the poorest cognitive performance at the start of the study, extended time in bed and waking up later were associated with higher rates of dementia. Based on these patterns, the researchers suggested that late waking times and extended time in bed may reflect early symptoms of cognitive decline that eventually develop into dementia. On the other hand, since short time in bed was associated with dementia only in those without cognitive problems at baseline, they suggested that shorter time in bed was a risk factor for dementia. Efforts to ensure older adults are getting more than six hours of sleep per night could reduce their chances of developing dementia.
Bokenberger K, Strom P, Dahl Aslan AK, et al. Association between sleep characteristics and incident dementia accounting for baseline cognitive status: a prospective population-based study. Journals of Gerontology Series A: Biological Sciences and Medical Sciences (2016); 72(1): 134–139.