A good night’s sleep may be another way to help improve an aging brain, research suggests.
A new study, published Tuesday in the peer-reviewed journal Nature Communications, found sleep duration of six hours or less a night for those aged 50 to 60 was associated with a 30% increase risk of late-onset dementia compared to consistent normal sleep of seven hours.
Participants reported how many hours they slept on anaverage weeknight in questionnaires completed six times between 1985 and 2016. Their medical records were drawn from a previous study called Whitehall II, which began in the mid-1980s.
Out of nearly 8,000 people, researchers found 521 had been diagnosed with dementia at an average age of 77.
The length and sample size of the study make its results significant, experts say, and help to fill in gaps left by previous five- or 10-year studies.
“We know that changes in sleep are commonly reported in individuals with dementia,” said Claire Sexton, director of scientific programs and outreach at the Alzheimer’s Association. “There has been a chicken and the egg debate about what comes first and whether impaired sleep is a consequence of having dementia or whether it can be a contributing factor to its development.”
Previous studies have suggested long sleep duration also may be associated with an increased risk of dementia, however, study authorsin Tuesday’s reportsaid they found no evidence to support that hypothesis.
Sexton speculates the link between long sleep duration and dementia may be inconsistent because fewer people sleep longer than an average of seven hours per night compared to those who sleep less than six hours. A small sample size may impact results.
More studies are needed to understand the mechanism behind how sleep could impact dementia, said Kristine Wilckens, assistant professor of psychiatry at the University of Pittsburgh School of Medicine, who was not involved with the study.
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But experts have hypothesized from previous studies that sleep may help clear away the buildup of abnormal protein deposits characteristic of Alzheimer’s disease.
“Parts of the brain involved with sleep-wake regulation tend to have early neurodegeneration,” she said. “Proteins involved by Alzheimer’s disease are influenced by the sleep-wake cycle and clearance of those pathological proteins are greater during sleep.”
Although the study’s length and sample size help to reinforce its results, experts say the study has some limitations. For example, the participants involved in the earlierWhitehall study were not representative of all socioeconomic statuses and racial or ethnic populations.
“The study was founded in the 1980s and based upon U.K. civil servants … this was predominately white male (and) healthier than the general population,” Sexton said.
According to a report by the U.S. Department of Health and Human Services, the prevalence rates of Alzheimer’s disease – a form of dementia – ranges from 14% to 500% higher among Black Americans than among whites.
Wilckens says the study doesn’t take into account quality of sleep, which she said also could have an impact on cognitive function later in life.
While there may be limitations to the study, experts say it highlights the importance of sleep and how certain behaviors can contribute to the risk of developing dementia. Americans can use this information to not only change their sleep habits but also incorporate a healthy diet and daily physical exercise to help reduce that risk.
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
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