A new longitudinal study finds people who take “excessive” naps during the daytime are at higher risk of Alzheimer’s dementia, but the study also showed that a diagnosis of Alzheimer’s led to increases in daytime napping in the years following diagnosis.
The study and its bi-directional findings suggest that the interaction of sleep and cognitive decline warrants further study. It was published in the journal Alzheimer’s & Dementia.
Daytime napping is common in older adults, but its implications on cognitive function, alertness, and mood remain controversial. Most of the studies looking at Alzheimer’s disease and daytime napping have tended to use measures such as questionnaires that aren’t always a reliable source of data. Most have been based on cross-sectional research rather than longitudinal studies that follow people over time.
A team of researchers including Peng Li, Ph.D., of Brigham and Women’s Hospita lin Boston, wanted to better understand sleep and cognitive function patterns over time, so they turned to the Rush University Memory and Aging Project, a long-term effort to track memory, mobility, and strength among a cohort of patients in the later years of their lives. The Rush study includes sleep data tracked objectively using actigraphy measured by devices worn on participants’ non-dominant wrists for up to 14 days. The patients in the study were, on average, 81-years-old, and the study’s follow-up period was up to 14 years.
Li and colleagues’ analysis showed that older adults had more frequent naps as they aged, and that patients with Alzheimer’s dementia saw their nap duration and frequencies more than double each year as their dementia progressed. However, while cognitive decline was predictive of excessive napping, excessive daytime napping was also predictive of worse cognition the following year.
Li told Managed Healthcare Executive®that there could be multiple reasons for the apparent bi-directional nature of the relationship between excessive napping and cognitive impairment. It could be that both are due to underlying pathopsychological changes brought on by Alzheimer’s, but it could also be that both excessive napping and Alzheimer’s share a common pathological mechanism.
Another possibility, he said, is that napping itself leads to neurodegeneration.
“One potential speculation is that ‘excessive’ napping may interfere with our circadian clocks that have been shown to play a role in the clearance of amyloid beta,” he said. “In a prior study from us, we demonstrated that circadian disturbances may independently predict future risk of Alzheimer’s dementia, and the conversion from mild cognitive impairment to dementia, in older adults.”
However, Li said further study would be needed to isolate and verify the mechanisms of the associations identified in this study. He said it is not clear whether interventions to curb excessive daytime napping would lead to cognitive benefits, and he noted that there is evidence that short early afternoon naps can be helpful. Thus, one question that still needs to be answered is where the line between “healthy” and “excessive” napping lies.
Broadly speaking, Li said waking up groggy or drowsy after a nap could be a sign that a person is napping for too long. He noted that one immediate problem of excessive daytime naps is that they can prevent the build-up of “sleep drive,” the urge to go to sleep at nighttime.
In terms of clinical implications, Li said it’s too early to say exactly how this research might affect day-to-day patient care. He also pointed out that the findings relate specifically to older adults, and may not apply to young or middle-aged adults.
Another important question, he said, is whether the naps are planned or unplanned, as dozing off unconsciously might have different healthcare implications than intentional napping. For now, he said, napping and sleepiness questions need to be addressed on a case-by-case basis. However, he said older patients and their physicians should take note if the patient experiences significant shifts in sleep patterns.
“[B]ased on our current study, I think it is worthy of further medical attention should there be drastic changes in the napping behavior of older adults,” he said.