Daytime napping and Alzheimer's dementia: A potential bidirectional relationship.

INTRODUCTION: Daytime napping is frequently seen in older adults. The longitudinal relationship between daytime napping and cognitive aging is unknown. METHODS: Using data from 1401 participants of the Rush Memory and Aging Project, we examined the longitudinal change of daytime napping inferred objectively by actigraphy, and the association with incident Alzheimer's dementia during up to 14-year follow-up. RESULTS: Older adults tended to nap longer and more frequently with aging, while the progression of Alzheimer's dementia accelerates this change by more than doubling the annual increases in nap duration/frequency. Longer and more frequent daytime naps were associated with higher risk of Alzheimer's dementia. Interestingly, more excessive (longer or more frequent) daytime napping was correlated with worse cognition a year later, and conversely, worse cognition was correlated with more excessive naps a year later. DISCUSSION: Excessive daytime napping and Alzheimer's dementia may possess a bidirectional relationship or share common pathophysiological mechanisms.