Decline in Slow-Wave Sleep Linked to Increased Dementia Risk

Researchers have identified a potential link between decreased slow-wave sleep (SWS)—a crucial sleep cycle phase—and Alzheimer risk. The prospective cohort study, published in JAMA Neurology, substantiates an emerging body of research suggesting that SWS supports the aging brain, including facilitating the glymphatic clearance of proteins that aggregate in Alzheimer disease.

“SWS percentage declines over time in adults 60 years and older and...greater declines are associated with the risk of future dementia. APOE ε4 genotype was independently associated with greater SWS percentage loss with aging,” Jayandra J Himali, PhD, Boston University School of Medicine, Massachusetts, and co-authors wrote in the study. “However, greater SWS percentage decline was associated with a higher risk of incident dementia independent of APOE ε4 status. Although we cannot rule out residual confounding, these data suggest SWS loss as a dementia risk factor.”

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The study included a cohort of participants (N = 346) from the Framingham Heart Study with a mean age of 69 years who were followed for 17 years and completed 2 overnight polysomnography (PSG) studies in either 1995 to 1998 or 1998 to 2001. To be included in the current study, participants needed to be over 60 years old and not diagnosed with dementia at the time of the second overnight PSG. A portable PSG system was used for the at-home all-night sleep assessments to measure the percentage change in SWS.

Over the follow-up period, there were 52 cases of incident dementia, with each percentage decrease in SWS being associated with a 27% increase in dementia risk (hazard ratio, 1.27; 95% CI, 1.06-1.54; P = .01). Individuals carrying a genetic risk for Alzheimer disease, such as carrying the APOE ε4 allele, demonstrated a quicker decline in SWS with aging than those without, the study found.  Additionally, hippocampal volume was not associated with changes in SWS percentage, adjusting for age, sex, cohort, and APOE ε4 allele status (β [SE] = −0.40 [0.25]; P = .11).

“Because both APOE and the sleep-wake cycle are involved in amyloid production and/or clearance, further research is required to determine their synergistic effects on dementia risk,” researchers concluded. 

Reference
Himali JJ, Baril AA, Cavuoto MG, et al. Association between slow-wave sleep loss and incident dementia. JAMA Neurol. Published online October 30, 2023. doi:10.1001/jamaneurol.2023.3889