Getting sufficient sleep supports overall health, and research indicates it may also influence dementia risk later in life. A 2023 study showed that adults over 60 faced a 27 percent higher chance of developing dementia for each 1 percent annual reduction in slow-wave sleep. This stage occurs in the third phase of the typical 90-minute sleep cycle and lasts roughly 20 to 40 minutes. During this period brain activity, heart rate, and blood pressure all decrease. Slow-wave sleep aids muscle and bone strength, bolsters immunity, and readies the brain for new information. Separate findings revealed that people showing Alzheimer-related brain changes performed better on memory tasks when they obtained more of this deep sleep. Neuroscientist Matthew Pase of Monash University noted that slow-wave sleep helps clear metabolic waste from the brain, including proteins linked to Alzheimer’s disease. Researchers tracked 346 participants from the Framingham Heart Study who underwent overnight sleep monitoring twice, first between 1995 and 1998 and again between 2001 and 2003. None had dementia at the second assessment, and all were over 60 by 2020. Follow-up continued through 2018, during which 52 cases of dementia were identified. Slow-wave sleep declined steadily after age 60, with the steepest drop between 75 and 80 before stabilizing. Each yearly percentage-point loss correlated with a 27 percent rise in dementia risk and a 32 percent increase for Alzheimer’s specifically. Lower levels also associated with cardiovascular issues, certain medications, and the APOE ε4 gene variant. The study design shows associations only and cannot establish causation; further work is needed. The findings appeared in JAMA Neurology.
