MELBOURNE, Australia — It’s common knowledge that sleep is important for our overall health and well-being. Now, researchers in Australia are adding to that, revealing the crucial role that deep sleep can play in avoiding dementia. Scientists at Monash University report that even a one-percent reduction in deep sleep annually can lead to a 27-percent increased risk of dementia for people over the age of 60.
All in all, these findings make a strong case for all of us to prioritize deep sleep, also known as slow-wave sleep, as we grow older. If you’re wondering what exactly separates “deep sleep” from the rest of your nightly shuteye, slow wave sleep is the third stage of non-REM sleep and is essential for waking up feeling rested and refreshed. Characterized by diminished brain wave activity, as well as slower breathing and a slower heart rate, deep sleep usually lasts around an hour to an hour-and-a-half and occurs early in the night.
Led by Associate Professor Matthew Pase, from the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health, this project examined a total of 346 people (all over the age of 60) who had been enrolled in the Framingham Heart Study and completed two overnight sleep studies in the periods spanning 1995-1998 and 2001-2003 (average of five years between the two studies).
These individuals were carefully tracked for dementia diagnoses starting from the time of the second sleep study all the way until 2018. Researchers uncovered that, on average, the amount of deep sleep declined between the two studies. This suggests that slow-wave sleep loss occurs as we age.
Over the following 17 years, study authors noted 52 cases of dementia. Importantly, even after they adjusted for age, sex, cohort, genetic factors, smoking status, sleeping medication use, antidepressant use, and anxiolytic use, each percentage decrease in deep sleep annually remained associated with a 27-percent increase in dementia risk.
“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 Alzheimer’s disease,” Associate Professor Pase says in a university release.
“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.”
Associate Professor Pase explains that the Framingham Heart Study is a unique community-based cohort including repeated overnight polysomnographic (PSG) sleep studies — meaning scientists recorded brain waves — as well as uninterrupted surveillance for signs of dementia.
“We used these to examine how slow-wave sleep changed with aging and whether changes in slow-wave sleep percentage were associated with the risk of later-life dementia up to 17 years later,” Pase concludes.
“We also examined whether genetic risk for Alzheimer’s Disease or brain volumes suggestive of early neuro-degeneration were associated with a reduction in slow-wave sleep. We found that a genetic risk factor for Alzheimer’s disease, but not brain volume, was associated with accelerated declines in slow wave sleep.”
The study is published in JAMA Neurology.
8 healthy habits that lower Alzheimer’s risk
While scientists work on new drugs to help those displaying symptoms or at a high-risk for Alzheimer’s disease, there are a number of drug-free steps you can take to lower your chances of developing Alzheimer’s in the first place.
- Being active
- Eating better
- Losing weight
- Not smoking
- Maintaining healthy blood pressure
- Controlling cholesterol
- Reducing blood sugar
- Get good quality sleep
“These healthy habits in the Life’s Simple 7 have been linked to a lower risk of dementia overall,” Professor Adrienne Tin from the University of Mississippi says in a statement. “But it is uncertain whether the same applies to people with a high genetic risk.”
“The good news is even for people who are at the highest genetic risk, living by this same healthier lifestyle are likely to have a lower risk of dementia,” Prof. Tin adds.
You might also be interested in:
- Deep sleep can protect older adults from Alzheimer’s-related memory loss
- Deep sleep a natural ‘Fountain of Youth’ in old age, study says
- Number of dementia cases by 2040 could be shockingly higher than estimates predicted
