Just how important is a good night’s sleep? And what defines a night of sleep as being ‘good’ anyway? As a result of a new study, we may be able to answer the first question with the answer to the second. And, according to new research, deep sleep is at least part of the answer to the second question.
That research, undertaken at Monash University in Melbourne, indicates that not getting enough deep sleep dramatically increases your risk of dementia. For people over 60, a reduction of just 1 per cent in deep sleep translates to a 27 per cent increase in dementia risk, according to the research.
Deep sleep or deep trouble
Monash School of Psychological Sciences’ Associate Professor Matthew Pase, who led the study, says deep sleep – known technically as ‘slow-wave’ sleep – supports the ageing brain in many ways.
Chief among those is getting rid of the proteins that form the brain ‘plaque’ associated with Alzheimer’s disease.
“We know that sleep augments the clearance of metabolic waste from the brain,” he says. This includes “facilitating the clearance of proteins that aggregate in Alzheimer’s disease”.
The new research helps to clarify the effect of deep sleep, which was previously unclear.
“To date, we have been unsure of the role of slow-wave sleep in the development of dementia,” Assoc. Prof. Pase says. “Our findings suggest that slow-wave sleep loss may be a modifiable dementia risk factor.”
A study in sleep
The new study, undertaken jointly with Melbourne’s Turner Institute for Brain and Mental Health, has been published in JAMA Neurology. It looked at 346 participants, aged over 60, enrolled in the Framingham Heart Study.
The participants completed two overnight sleep studies from 1995 to 1998 and 2001 to 2003. There was an average of five years between the two studies.
The participants were then carefully followed for dementia from the time of the second sleep study through to 2018. The researchers found, on average, that the amount of deep sleep declined between the two studies, indicating slow-wave sleep loss with ageing.
After 17 years of follow-ups, 52 cases of dementia were identified. The study found that the percentage decrease in deep sleep each year was associated with a 27 per cent increase in the risk of dementia.
This remained so even after adjusting for age, sex, cohort, genetic factors and smoking status. Adjustment was also made for the use of sleeping medications, antidepressants and anxiolytics, and the risk remained the same.
Are there factors other than deep sleep at play?
Assoc. Prof. Pase and his colleagues did consider the potential involvement of other factors and, as a result, found genetics could play a role.
“We also examined whether genetic risk for Alzheimer’s disease or brain volumes suggestive of early neurodegeneration were associated with a reduction in slow-wave sleep,” he says.
“We found that a genetic risk factor for Alzheimer’s disease … was associated with accelerated declines in slow-wave sleep.” Brain volume, however, did not appear to be a factor.
There is a relatively common perception that older people need less sleep. This idea was previously debunked, and this new study further refutes that perception. Sleep remains just as important as you get older, and getting enough deep sleep could well save you from dementia.
Has the amount of sleep you get each day changed as you’ve grown older? Does the amount of sleep you get affect your wellbeing? Let us know via the comments section below.
Also read: How can I get some sleep? Which treatments actually work?
