A good night’s sleep is vital for the health and proper functioning of our body
Scientists have discovered the phase of sleep that reduces the risk of dementia, Science Alert reported, citing a publication in JAMA Neurology.
A good night’s sleep is vital for the health and proper functioning of our body. However, its importance extends much further than is assumed, scientists point out.
According to research, as you age, the risk of developing dementia increases if you do not get enough deep (slow-wave) sleep. A study found that in people over 60, the likelihood of developing dementia jumps by 27 percent if they lose just 1 percent of this deep sleep each year.
Deep sleep is the third stage of the 90-minute most important sleep cycle in humans and lasts between 20 and 40 minutes. This is the phase that brings the most rest – then brain waves and heart rate slow down, and blood pressure drops. Deep sleep also strengthens our muscles, bones and immune system, while preparing the brain to absorb new information.
“Slow-wave or deep sleep supports the aging brain in many ways. We know that sleep enhances the removal of metabolic waste from the brain, including by facilitating the clearance of proteins that accumulate in Alzheimer’s disease,” explains neuroscientist Matthew Pace of Monash University in Australia.
“Until now, however, we were not sure exactly what role deep sleep plays in the development of dementia. Our findings suggest that the loss of this phase may be a risk factor that can be modified and controlled,” he adds.
Pace and his colleagues from Australia, Canada and the United States studied 346 participants in the Framingham Heart Study. They underwent two sleep studies, the first between 1995 and 1998 and the second between 2001 and 2003, with an average of five years between the two tests.
This group of people, who had no history of dementia at the time of the 2001–2003 studies and who were over 60 years old in 2020, allowed the researchers to examine the relationship between the two factors over time. They compared data from the two in-depth polysomnography sleep studies and then tracked the participants’ development of dementia through 2018.
“We used these data to examine how deep sleep changes with age and whether changes in the percentage of slow-wave sleep are associated with the risk of developing dementia later in life—up to 17 years later,” Pace says.
During the 17-year follow-up, 52 cases of dementia were recorded among the participants. The levels of deep sleep recorded in the studies were also analyzed for a possible link to these cases. Overall, the duration of deep sleep was found to decline after age 60, with this loss peaking between ages 75 and 80, then leveling off.
Comparing the participants’ first and second sleep studies, the researchers found an association between each percent decline in deep sleep per year and a 27 percent higher risk of developing dementia. This risk increased to 32 percent when the researchers focused specifically on Alzheimer’s disease, the most common form of dementia.
The Framingham Heart Study measures a range of health indicators over time, including shrinkage of the hippocampus—an early sign of Alzheimer’s—and common factors that contribute to cardiovascular disease. Low levels of deep sleep have been linked to a higher risk of cardiovascular disease, taking medications that can affect sleep, and having the APOE ε4 gene, which is linked to Alzheimer’s disease.
“We found that the genetic risk factor for Alzheimer’s disease is associated with an accelerated decline in deep sleep, but not brain volume,” Pace explains.
While these links are clear, the authors note that this type of study does not definitively prove that a lack of deep sleep causes dementia. It’s entirely possible that brain processes associated with dementia are responsible for the sleep loss. More research is needed to fully understand these factors, the researchers say.
In the meantime, though, we can certainly prioritize quality sleep—it’s important for much more than just boosting our memory. There are even specific steps you can take to increase your chances of getting more hours of that precious deep sleep, scientists say.
Illustrative photo: pexels-polina-kovaleva-6541082
