The risk of developing dementia may increase as you age if you don’t get enough slow-wave sleep. People over 60 are 27% more likely to suffer from dementia if they lose just 1% of that deep sleep each year, according to a new study.
Slow-wave sleep is the third stage of a 90-minute human sleep cycle, which lasts approximately 20 to 40 minutes. This is 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 brain to absorb more information. Earlier this year, research found that people with brain changes linked to Alzheimer’s disease performed better on memory tests when they got more slow-wave sleep.
“Slow wave sleep, or deep sleep, supports brain aging in several ways, and we know that sleep increases the removal of metabolic waste from the brain, including facilitating the removal of proteins that aggregate in brain disease. Alzheimer’s,” says neuroscientist Matthew Pase. from Monash University in Australia.
“However, so far we are uncertain about the role of slow-wave sleep in the development of dementia. Our results suggest that loss of slow-wave sleep may be a modifiable risk factor for dementia.”
Pase and colleagues from Australia, Canada, and the United States examined 346 participants in the Framington Heart Study who completed two nighttime sleep studies between 1995 and 1998 and between 2001 and 2003, with an average of five years between testing periods.
This community cohort, which had no cases of dementia at the time of the study from 2001 to 2003 and was over 60 years old in 2020, gave researchers the opportunity to examine the link between two factors over time. time by comparing datasets from the two comprehensive sleep polysomnography studies, then monitoring dementia in participants through 2018.
“We used these to examine how slow-wave sleep changed with aging and whether changes in the percentage of slow-wave sleep were associated with dementia risk later in life up to 17 years later,” says Pase.
During the 17 years of follow-up, 52 cases of dementia were recorded among the participants. Participants’ slow-wave sleep levels recorded in sleep studies were also examined to determine a link to cases of dementia.
Overall, their rate of slow-wave sleep declines from age 60, with this loss peaking between ages 75 and 80, then stabilizing thereafter.
Comparing the first and second studies of participants’ sleep, researchers found a link between each percentage point decrease in slow-wave sleep per year and a 27% increased risk of developing dementia.
This risk increased to 32% when they focused on Alzheimer’s disease, the most common form of dementia.
The Framington Heart Study measures several health data points over time, including hippocampal volume loss (an early sign of Alzheimer’s disease) and common factors contributing to cardiovascular disease.
Low levels of slow-wave sleep were associated with a higher risk of cardiovascular disease, taking medications that can impact sleep, and having the APOE ε4 gene, which is linked to Alzheimer’s disease.
“We found that a genetic risk factor for Alzheimer’s disease, but not brain volume, was associated with an accelerated decline in slow-wave sleep,” says Pase.
While these are clear associations, the authors note that this type of study does not prove that loss of slow-wave sleep causes dementia, and it is possible that dementia-related brain processes cause loss of sleep. sleep. For these factors to be fully understood, additional research is needed.
We can definitely prioritize getting enough sleep while we wait – it’s important for more than just strengthening our memory. There are even steps you can take to increase your chances of getting more of that crucial slow-wave sleep.
The study was published in JAMA Neurology.