A recent study reveals that a mere 1% reduction in deep sleep in individuals aged 60 and above can amplify the likelihood of dementia by 27%. The study also suggests that preserving or enhancing deep sleep, often referred to as slow-wave sleep, in older individuals may serve as a preventive measure against dementia.
Conducted by Associate Professor Matthew Pase, from the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health in Melbourne, Australia, the research was published in JAMA Neurology. It involved 346 participants, all over the age of 60, who were part of the Framingham Heart Study. These individuals underwent two overnight sleep studies between 1995 and 1998 and 2001 to 2003, with an average of five years between the two assessments.
The participants were then closely monitored for dementia from the second sleep study until 2018. The study’s findings indicated a decline in deep sleep over time, signifying a reduction in slow-wave sleep associated with aging. During the 17-year follow-up, there were 52 cases of dementia. Even after adjusting for variables like age, sex, cohort, genetic factors, smoking habits, sleeping medication usage, antidepressant usage, and anxiolytic medication usage, the study revealed that each annual percentage decrease in deep sleep correlated with a 27% increase in the risk of dementia.
Associate Professor Pase commented on the significance of slow-wave sleep, stating that it plays a crucial role in supporting the aging brain, including aiding in the removal of metabolic waste from the brain, which includes the clearance of proteins that tend to aggregate in Alzheimer’s disease.
He further stated, “To date, we have been unsure of the role of slow-wave sleep in the development of dementia. Our findings suggest that slow-wave sleep loss may be a modifiable risk factor for dementia.”
Associate Professor Pase emphasized the unique nature of the Framingham Heart Study, which involves a community-based cohort and repeated overnight polysomnographic (PSG) sleep studies, along with continuous monitoring for incident dementia.
“We utilized these data to examine how slow-wave sleep changes with aging and whether alterations in the percentage of slow-wave sleep are associated with the risk of dementia in later life, spanning up to 17 years,” he explained. “We also investigated whether genetic susceptibility to Alzheimer’s disease or indications of early neurodegeneration in brain volume were linked to a reduction in slow-wave sleep. Our findings revealed that a genetic predisposition for Alzheimer’s disease, but not brain volume, correlated with accelerated declines in slow-wave sleep.”
