Alzheimer disease (AD) dementia may share common pathophysiological mechanisms or be bidirectionally related with excessive daytime napping, according to results of a study published in Alzheimer’s & Dementia.
This analysis used data from the Rush Memory and Aging Project, which is an ongoing, prospective, observational cohort study that began in 1997. Yearly, participants have been assessed by a battery of neuropsychological and cognitive testing.
Since 2005, participants (N=1401) were given a watch-like Actical device which monitors motor activity. Sleeping between 9 am and 7 pm, detected by the Actical device, was defined as daytime napping. Engaging in daytime napping was related with progression of AD dementia.
The study population comprised 76.6% women, aged mean 81.42±7.47 years, with 15.04±3.02 years of education, they slept for 5.69±1.45 hours per night, took a median of 1.80 (interquartile range [IQR], 0.90-3.35) naps per day, napping on average for 46.60 (IQR, 21.95-93.10) minutes per day.
Nap frequency and duration were positively correlated (ρ, 0.91; P <.0001) and age was positively correlated with nap frequency (r, 0.23; P <.0001) and duration (r, 0.21; P <.0001).
Among the subset of individuals with sufficient actigraphy data (n=1065), 812 had no cognitive impairment (NCI) at baseline and went on to develop mild cognitive impairment (MCI; n=384) or AD dementia (n=146), 209 had MCI at baseline with 101 developing AD dementia, and 44 had AD dementia at baseline.
Nap duration increased over time among the NCI cohort (mean annual increase, 11.31 min; P <.0001), doubling after the onset of MCI (mean annual increase, 24.66 min; P <.0001), and tripling after AD dementia onset (mean annual increase, 68.35 min; P <.0001). A similar pattern was observed for napping frequency.
Among the 1203 participants with sufficient data, longer naps (hazard ratio [HR], 1.20; 95% CI, 1.06-1.35; P =.004) and more frequent naps (HR, 1.23; 95% CI, 1.08-1.39; P =.001) associated with the development of AD dementia. The effect of 1 standard deviation (SD) increase in nap duration was equivalent to aging by 1.6 years and 1 SD increase in frequency with aging by 1.9 years.
The results of this study may not be generalizable to a younger population of individuals as these data were sourced from an older population.
The study authors concluded, “These results show that participants tended to nap longer and more frequently with aging. Most importantly, the progression of Alzheimer’s dementia appeared to accelerate this aging effect by doubling or more than doubling the annual changes (increases) in nap duration/frequency. Our results also show that longer and more frequent daytime naps were associated with higher risk of developing Alzheimer’s dementia.”
Li P, Gao L, Yu L, et al. Daytime napping and Alzheimer’s dementia: A potential bidirectional relationship. Alzheimer’s Dement. 2022;1–11. doi:10.1002/alz.12636