Lack of Deep Sleep May Lead to 27 Percent Increase in Risk of Dementia, Study Finds

Lack of deep sleep may be a dementia risk factor, suggesting better deep sleep could be a preventative tool against the common disease.

Past age 50, men are much more likely to have REM sleep behavior disorder than women. Ground Picture/Shutterstock

A mere 1 percent loss in a deep sleep each year could lead to a 27 percent increased risk of dementia for people over 60, according to a new study by Monash University.

The multi-year study which first began in 1995, examined 346 people over the age of 60 and found that 52 individuals had some form of dementia cases linked to declining sleep quality.

Research lead, Associate Professor Mattew Pase, said good sleep quality also supports the aging brain in many ways.

“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,” he said.

Additionally, the Monash University research investigated if genetic Alzheimer’s Disease or early signs of brain shrinkage were linked to decreased sleep quality.

“We found that a genetic risk factor for Alzheimer’s disease, but not brain volume, was associated with accelerated declines in slow-wave sleep,” he said.

Mr. Pase added deep sleep is “critically important” for an ageing brain.

Patients’ results were from the Framingham Heart Study—sleep and dementia studies.

MRI brain scan of a dementia patient with left parietal atrophy asymmetry. Atthapon Raksthaput/Shutterstock

Sleep is Important 10 to 20 Years Before Dementia Onset

Further, Mr. Pase told Today Extra that deep sleep benefits extend beyond dementia risk and apply to anyone at any age.

“Although we think of dementia as a condition of old age, the diseases that contribute to dementia can actually start at 10 or 20 years before dementia onset,” he said.

He added if people have dementia in their 70s, it often begins to develop during mid-life.

“So what we do when we’re 40 and 50 is critically important for what our brain looks like when we’re, say, 70, 80, and 90.”

Mr. Pase recommended that people try to maintain their level of deep sleep as they age, saying that it was better than aiming for set hours of deep sleep per night.

When asked if napping during the day was also critical, he said, “If you are napping and it’s making you feel more restored ... then that seems like a good thing.”

He added napping wasn’t studied as part of the research.

Tackling the Cause of Disrupted Sleep

However, other research found the root cause of the increased risk of developing dementia was sleep apnea (lack of oxygen to the brain during sleep), which leads to a lack of deep sleep.

The University of Queensland (UQ) Brain Institute Professor Elizabeth Coulson conducted the study on mice.

Ms. Coulson said, “We found sleep deprivation alone in mice caused only mild cognitive impairment.”

“But we developed a novel way to induce sleep-disrupted breathing and found the mice displayed exacerbated pathological features of Alzheimer’s disease,” she said.

“It demonstrated that hypoxia—when the brain is deprived of oxygen—caused the same selective degeneration of neurons that characteristically die in dementia.”

Professor Coulson said the next step involves determining the critical level of oxygen deprivation that leads to brain degeneration.

Around 50 percent of older adults have obstructive sleep apnoea, causing their breathing to stop and start.

However, Ms. Coulson said not everyone with obstructive sleep apnoea would develop dementia, but the focus should be on defining the at-risk population.

The current gold standard sleep apnoea treatment is a CPAP (continuous positive airway pressure) machine, which keeps the airway open during sleep and allows oxygen to the brain.

Ms. Coulson said that although CPAP couldn’t fit on mice, the alternative hypoxia prevention stopped the cognitive impairment and neuron death and also reduced Alzheimer’s pathology.

She said, “This suggests that CPAP treatment of obstructive sleep apnoea has the potential to reduce dementia risk.”

However, she said 30 percent of people with obstructive sleep apnoea fitted for CPAP machines already display signs of dementia-like cognitive impairment.

“Unfortunately, the hospital system isn’t referring those people to dementia clinics,” she said.

Notably, some dementia clinicians said their patient’s memory improved after their sleep problems were identified and treated.

“Early-stage human trials are underway with sleep clinicians in Brisbane and Sydney to determine the correlation between hypoxia and sustained cognitive impairment, and whether CPAP can reduce dementia risk,” she said.

“I would strongly recommend anyone with obstructive sleep apnoea use a CPAP machine to maintain cognitive function, as well as assist with other health issues.”