Short sleep may cancel mental benefits gained from exercise
In 8,958 persons in England who were 50 years of age and older, researchers examined cognitive function over a period of ten years.
According to the study, persons who get between 6 and 8 hours of sleep each night and who exercise more frequently had superior cognitive function.
Even if they engaged in higher levels of physical activity, people who slept for fewer than 6 hours per night exhibited a more rapid deterioration in cognitive function over ten years.
The advantages of higher levels of physical activity on cognitive function appeared to be preserved among participants aged 70 and older regardless of the quantity of sleep.
Physical activity appears to be good for the brain and may help prevent the onset of neurodegenerative diseases including dementia and Parkinson’s disease, according to existing research. A recent study discovered that sleep deprivation can lessen the advantages of exercising.
According to a 2022 nationally representative survey on the prevalence of cognitive impairment, 22% of Americans aged 65 and older have mild cognitive impairment and about 10% have dementia.
Numerous studies have revealed that exercise may lower the risk of dementia. More research continues to link a lack of sleep to a higher risk of dementia.
“Physical activity and sleep are factors that are thought to independently contribute to cognitive function, but they are also interrelated, where more physical activity is correlated with better quality sleep and physical activity may also regulate circadian rhythms,” said Mikaela Bloomberg, Ph.D.
Few studies that examined the effects of physical activity and sleep on cognitive function have been conducted, according to a team of UCL academics led by Bloomberg. Small and cross-sectional studies, which gather information from participants at a specific point in time, were the type of research they discovered.
Study is based on healthy people’ self-reported data.
Researchers from UCL analyzed longitudinal data from the English Longitudinal Study of Ageing (ELSA), which included 8,958 cognitively healthy people from England who were 50 years and older. The information was gathered from January 1, 2008, to July 31, 2019.
Every two years, participants provided reports on how much they moved and how long they slept.
Participants were asked how many hours they typically slept on a weeknight by researchers. The UCL researchers then classified sleep as “long” if it lasted longer than eight hours, “optimal” if it lasted between six and eight hours, and “short” if it lasted fewer than six hours.
Participants’ level of exercise was also questioned by researchers. Participants gave information about how often they engaged in light, moderate, and strenuous physical activity as well as whether they worked out more than once a week, once to three times a week, rarely, or never.
Using the immediate and delayed recall tests from the Consortium to Establish a Registry for Alzheimer’s disease, researchers evaluated the participants’ episodic memory. Participants were given a list of ten words by researchers, and they were asked to recall the terms both right away and a day later. The participants’ verbal fluency was also evaluated by the researchers using a test in which they had to name as many animals as they could in one minute.
Participants who disclosed receiving a dementia diagnosis during the follow-up period as well as those whose test results indicated some degree of cognitive impairment were excluded by the UCL researchers. Researchers also took into account information like whether participants had previously taken the same cognitive test when adjusting their analyses.
How do sleep duration and activity affect cognitive scores?
1,525 participants (50%) of the 3,069 participants who were assigned to the “higher physical activity category” said they exercised lightly, moderately, or vigorously more frequently than once per week. Another 1,161 individuals (37.8%) said they exercised lightly and moderately more frequently than once per week and vigorously once or twice per week.
2,384 (40.5%) of the 5,889 participants in the lower physical activity category said they did no vigorous exercise but did more than weekly mild and moderate exercise. Another 1,511 people (25.7%) said they did no vigorous exercise, just light exercise more than once a week, and only moderate exercise once or less frequently.
Participants who exercised more frequently were more likely to get 6 to 8 hours of sleep each night. In addition, they had higher levels of education and affluence than those in the lower physical activity group, and they were more likely to be male, younger at baseline, married, or living with a partner. In comparison to individuals in the lower physical activity group, those in the greater physical activity group were more likely to not smoke, had lower body mass indices (BMI), fewer diagnoses of all chronic illnesses, and fewer depressive symptoms.
The long-term cognitive benefits of sound sleep
Regardless of how much sleep they had, participants from the higher physical activity group often had the highest baseline cognitive scores.
“However, for ages 50 and 60 years, those with higher physical activity and short sleep declined more rapidly such that after 10 years of follow-up, they had cognitive scores similar to those in the lower physical activity groups,” the UCL researchers wrote in their study report.
“We were surprised to see that the cognitive benefits associated with physical activity were reduced when participants had insufficient sleep duration, but these findings are certainly in line with previous research pointing to an important role of sleep in cognitive and physical recovery,” said Dr Bloomberg.
The cognitive advantages of exercise seemed to persist even in older participants (age 70 and above) who had trouble sleeping.
Dr. Vernon Williams, a sports neurologist, pain management expert, and founding director of the Cedars-Sinai Kerlan-Jobe Institute in Los Angeles’ Centre for Sports Neurology and Pain Medicine, told us he was glad to see research showing the value of sleep for long-term advantages in cognitive function.
The idea that sustaining physical health in the absence of optimum sleep health lowers the cognitive benefits of physical activity, along with evidence showing both exercise AND sleep are key elements for maintaining cognitive health, is convincing, according to Dr. Williams.
More study is required to determine how exercise and sleep affect brain function.
Ryan Glatt, a senior brain health coach and the FitBrain Program’s director at the Pacific Neuroscience Institute in Santa Monica, California, told CNN that he thought the study was “very interesting” but pointed out its shortcomings.
The accuracy of self-reported physical activity and sleep length may have problems, and Glatt noted that the potential presence of sleep disorders or the effects of specific medications were not taken into account.
Dr. Bloomberg thinks there might be a way to carry out this study without depending on the participants’ honesty.
“An interesting next step would be to use objective measures of sleep and physical activity—for example, using wrist-worn accelerometers—to see whether we observe similar results,” she said.
The UCL researchers hope to see a similar study conducted on a wider range of populations in the future. Dr. Bloomberg further stated that she would like “to extend the results to dementia.”
To increase the likelihood that the impacts of sleep on cognition and not the other way around, Dr. Bloomberg said, “We purposefully excluded those with dementia and those whose cognitive scores suggested cognitive impairment.” Future studies ought to look into how physical activity and sleep patterns affect dementia risk.
REFERENCES:
- https://www.medicalnewstoday.com/articles/lack-of-sleep-reduces-cognitive-benefits-of-exercise
- https://newatlas.com/health-wellbeing/sleep-cancel-benefits-exercise-brain-health/
- https://zeenews.india.com/health/how-lack-of-sleep-reduces-cognitive-benefits-of-exercise-research-reveals-2633381.html
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