Lack of Deep Sleep Linked to Increased Dementia Risk
TOPLINE:
Losing as little as 1% of deep sleep each year has been linked to a 27% increase in dementia risk, results of a retrospective cohort study show. Researchers suggest that prioritizing deep sleep — also known as slow-wave sleep (SWS) — at this age may lower dementia risk.
METHODOLOGY:
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A subset of individuals (n = 346) aged ≥ 60 from the Framingham Heart Study completed two overnight polysomnographic sleep studies in the time spans of 1995-1998 and 2001-2003, with an average of 5 years between studies.
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Investigators followed participants from around the time of the second sleep study to 2018 to screen them for dementia.
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The sample was screened for single-nucleotide polymorphisms known to be associated with Alzheimer’s disease (AD), and participants were categorized as high genetic risk above the 80th percentile, intermediate genetic risk between the 20th and 80th percentiles, and low genetic risk below the 20th percentile.
TAKEAWAY:
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Over a mean of 12 years after the second sleep study, 52 of the 346 participants developed dementia. Of these, 44 were diagnosed with AD.
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After adjusting for sex, age, apolipoprotein E (APOE) e4 allele, smoking status, sleeping medication use, antidepressant use, and anxiolytic use, each percentage decrease in SWS per year was associated with a 27% increase in the risk for all-cause dementia (adjusted hazard ratio [aHR], 1.27; P = .01) and a 32% increase in the risk for AD (aHR, 1.32; P = .006).
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SWS loss with aging was accelerated in participants with the APOE e4 allele.
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Investigators speculate that SWS may be critically important for clearing metabolic waste, including the proteins that aggregate in AD.
IN PRACTICE:
“Slow-wave sleep, or deep sleep, supports the ageing brain in many ways, and we know that sleep augments the clearance of metabolic waste from the brain, including facilitating the clearance of proteins that aggregate in Alzheimer’s disease,” lead investigator Matthew Pase, PhD, Monash University, Clayton, Victoria, Australia, wrote in a press release. “Our findings suggest that slow wave sleep loss may be a modifiable dementia risk factor.”
SOURCE:
Pase led the study, which was published online October 30 in JAMA Neurology.
LIMITATIONS:
There were no gold-standard AD biomarkers available, such as amyloid β or tau. Also, because of the observational nature of the study, investigators were unable to establish whether SWS loss causes dementia.
DISCLOSURES:
The study was funded by the National Institute on Aging, the National Institutes of Health, the National Health and Medical Research Council of Australia, the Alzheimer’s Association, and the Dementia Australia Research Foundation. Pase reported grants from the National Institute on Aging, the National Health and Medical Research Council of Australia, the Alzheimer’s Association, and Dementia Australia. Other disclosures are noted in the original article.
