Morning Naps in Elderly People May Reflect Dementia Risk

INDIANAPOLIS -- Elderly people who nap in the morning and not at other times of the day could be exhibiting very early signs of Alzheimer's dementia, a researcher suggested.

Data from the Rush Memory and Aging Project (MAP) hinted that 80-year-olds who napped in the morning (9-11 a.m.) may have an increased risk of Alzheimer's dementia during up to 17 years of follow-up. No other timeframe suggested an elevated risk.

However, other statistical models -- which were adjusted for comorbidities and other variables -- showed that early napping among elderly adults was no longer significantly associated with subsequent Alzheimer's dementia, said Chenlu Gao, PhD, of Brigham and Women's Hospital in Boston, at the annual SLEEP meeting here, hosted jointly by the American Academy of Sleep Medicine and the Sleep Research Society.

The findings should be considered preliminary and inconclusive, Gao told MedPage Today. "We certainly need to study this further to understand this relationship," she said.

Participants who took 100% of their naps in the morning had a roughly twofold increase in Alzheimer's dementia risk, Gao said, but the association was not seen after adjusting for comorbidities.

The analysis expands on earlier data from the Rush MAP cohort. Like other studies, that research suggested a bidirectional relationship between excessive daytime napping and increased dementia risk, with longer and more frequent daytime naps linked to worse cognition, and worse cognition linked to longer and more frequent naps.

The new analysis, according to data from the abstract, included 1,203 Rush MAP cohort participants with a mean age of 81 at enrollment who did not have dementia at baseline. A total of 77% were female. During follow-up, 30% were diagnosed with Alzheimer's dementia.

Napping episodes and frequency were identified with the aid of a watch-like sensor participants wore that recorded motor activity. Each prolonged period of non-activity during the day (9 a.m. to 7 p.m.) was considered to be a nap.

Daytime nap times were divided into five 2-hour periods labeled as morning (9-11 a.m.), noon (11 a.m. to 1 p.m.), early afternoon (1-3 p.m.), late afternoon (3-5 p.m.), and evening (5-7 p.m.).

Cox proportional hazards modeling was used to examine the potential impact of nap timing and frequency on subsequent diagnosis of Alzheimer's dementia.

In a model adjusted only for age, sex, education, and nighttime sleep duration, napping between 9 and 11 a.m. was associated with a 1.9-fold (95% CI 1.00-3.58, P=0.04) increase in Alzheimer's risk.

However, the association was found to be nonsignificant in models adjusted for comorbidities, APOE carrier status, and all examined covariates.

Gao noted that while daytime nap duration is known to increase with age, the findings suggest that nap timing may be important, with napping later in the day more consistent with healthy aging than taking earlier naps.

Study limitations cited by the researchers included the potential mislabeling of inactive periods as napping and the potential mislabeling of morning sleep as naps.

Gao said future areas of research include exploring the potential interaction of genetic risk for developing Alzheimer's dementia and nap timing, as well as examining whether nap timing interventions influence age-related cognitive decline.