Sleep Disturbances Increase the Risk of Dementia: A Systematic Review and Meta-analysis

Sleep disturbances and dementia are two common and significant health problems in older adults. Investigations suggest that sleep disturbances might increase the risk of dementia. The aim of the present study was to systematically review and meta-analyze the predictive roles of overall sleep disturbances, their subtypes (e.g., insomnia, sleep disordered breathing [SDB]), and other sleep problems (e.g., excessive daytime sleepiness, sleep-related movement disorder, circadian rhythm sleep disorder, and nonspecific sleep problems) in incident all-cause dementia and Alzheimer's disease (AD) and vascular dementia subtypes. We performed a systematic search of the PubMed, EMBase, ISI Web of Science, and PsycINFO databases for longitudinal studies that were published up to October 28, 2016. A total of 12,926 papers were retrieved. Eighteen longitudinal studies that included 246,786 subjects at baseline and 25,847 dementia cases after an average 9.49 y of follow-up were eligible for inclusion. Compared with individuals without sleep disturbances, subjects who reported sleep disturbances had a higher risk of incident all-cause dementia, AD, and vascular dementia. The subgroup analysis showed that insomnia increased the risk of AD but not vascular or all-cause dementia. In contrast, SDB was associated with a higher incidence of all-cause dementia, AD, and vascular dementia. This meta-analysis suggests that sleep disturbances may predict the risk of incident dementia. Moreover, insomnia was associated only with incident AD, and SDB was a risk factor of all-cause dementia, AD, and vascular dementia. However, sleep disturbances were evaluated mainly based on self-reports, and some confounders may mediate the relationship between sleep disturbances and dementia. Therefore, the results should be further validated. In summary, these findings may help identify individuals who are at risk for dementia and optimize early prevention strategies.