Sleep disturbance is associated with incident dementia and mortality

People with Alzheimer's disease (AD) commonly complain of sleep disturbances, which are seen in a wide variety of conditions that become more common in late life. It is not known whether sleep-related symptoms are associated with AD independently of their association with other illnesses. Secondary analyses of sleep-related measures collected through the Survey of Health, Ageing and Retirement in Europe (SHARE; i.e., sleeping problems, fatigue, taking sleeping medication, and trouble sleeping or a change in pattern) were conducted on those who reported the absence of AD or dementia at baseline. A 'sleep disturbance index' (SDI) using sleep-related measures was created and compared to a frailty index reflecting overall health status. Each sleep measure independently predicted self-reported AD or dementia and mortality within ~4 years. Combined, the SDI was associated with an increased risk of developing AD or dementia (OR= 1.23, 95%CI = 1.11-1.36) and mortality (OR = 1.18, 95% CI = 1.12-1.24), and remained a strong factor for dementia when overall health status was added to the risk model (p = 0.054). These findings indicate that sleep disturbance may exist prior to the manifestation of other typical symptoms observed in AD (e.g., memory loss). Sleep-related questions may be useful for screening individuals at risk for dementia and may allow for the earlier detection of AD at the preclinical stage.