The risk of getting dementia may go up as you get older if you don't get enough slow-wave sleep. Over-60s are 27 percent more likely to get dementia if they lose just 1 percent of this deep sleep each year, a 2023 study found. is the third stage of a human 90-minute sleep cycle, lasting about 20–40 minutes.
It's the most restful stage, where brain waves and heart rate slow and blood pressure drops. Deep sleep strengthens our muscles, bones, and immune system, and prepares our brains to absorb more information. In 2023, that individuals with Alzheimer's-related changes in their brain did better on memory tests when they got more slow-wave sleep.
"Slow-wave sleep, or deep sleep, supports the aging 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 disease," neuroscientist Matthew Pase from Monash University in Australia. "However, 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 dementia risk factor.
" Pase and colleagues from Australia, Canada, and the US examined 346 participants who had completed two overnight sleep studies between 1995 and 1998 and between 2001 and 2003, with an average of five years between testing periods. This community-based cohort, who had no record of dementia at the time of the 2001-2003 study, and were over 60 years old in 202.