Daytime napping increases risk of Alzheimer's disease in elderly: Study

USA: Yue Leng and colleagues reported in a recent study that older adults who take naps for more than an hour a day are at 40% higher risk for developing Alzheimer's disease (AD) versus their counterparts who took naps for less than one hour a day. Also, those who napped at least once a day were found to be at 40% higher risk for AD development versus those who did not nap once a day. The study appears in the journal Alzheimer's & Dementia.

The researchers' team from the USA further adds, "to the best of our knowledge, this is the first cohort study showing a bidirectional link between objectively measured, excessive daytime napping and Alzheimer's dementia or cognitive impairment."

In older adults, excessive daytime napping is frequently seen, mainly in those with Alzheimer's disease. This is proposed to be due to the arousal deficiency due to neuronal and neurotransmitter loss in wake-promoting neurons associated with tau tangles, one of the AD's pathological hallmarks. This results in sleep-wake disturbances and a higher propensity for daytime napping. Vice versa, excessive sleepiness during daytime, which may be a cause of long and frequent naps, has also been tied to faster cognitive decline or AD pathology build-up. However, the longitudinal relationship between daytime napping and cognitive aging is not known. 

Against the above background, the researchers' team aimed to clarify the association between daytime napping and Alzheimer's dementia by unraveling how the evolution of napping is intertwined with cognitive aging or the progression of Alzheimer's dementia.

The longitudinal change of daytime napping inferred objectively by actigraphy was examined, and the association with incident Alzheimer's dementia during up to 14-year follow-up using data from 1401 participants of the Rush Memory and Aging Project.