- Researchers looked at cognitive function over 10 years in 8,958 people aged 50 and over in England.
- The study found that people who slept between 6 and 8 hours per night and engaged in higher levels of physical activity were associated with better cognitive function.
- People who slept less than 6 hours a night, even if they engaged in higher levels of physical activity, experienced faster cognitive decline over ten years.
- Among participants aged 70 and older, the benefits of higher levels of physical activity on cognitive function appeared to be maintained despite the number of hours slept.
Evidence from existing research shows that physical activity is beneficial for brain health and can protect against the development of neurodegenerative conditions such as dementia and Parkinson’s disease. However, a new study found it lack of sleep may reduce such benefits from exercise.
Nearly 10% of adults age 65 and older in the United States have dementia, and another 22% have mild cognitive impairmentaccording to the national representative for 2022
“Physical activity and sleep are factors thought to independently contribute to cognitive function, but they are also interrelated, where greater physical activity is associated with better quality sleep, and physical activity can also regulate circadian rhythms,” Mikaela Bloomberg, Ph.D.research fellow at the Institute of Epidemiology and Healthcare, University College London, explained to Medical news today.
A team of UCL researchers, including Bloomberg, found little existing research looking at the impact of physical activity and sleep on cognitive function. The studies they found were small and
“Because sleep disturbances can be an early symptom of neurocognitive diseases such as dementia, which cause cognitive dysfunction, it is challenging to determine whether the results we observe in previous studies are due to the effects of sleep on cognitive function or vice versa,” said Dr. Bloomberg. “With this in mind, we wanted to examine how combinations of physical activity and sleepwear affected cognitive function over a long period of time.”
A paper by UCL researchers about their large, longitudinal study appears in
For their study, researchers from UCL used longitudinal data on 8,958 cognitively healthy adults in England aged 50 and over from English Longitudinal Study of Aging (ELSA). The data used were collected between January 1. 2008 and 31. July 2019.
The participants provided reports on their physical activity and sleep duration every two years.
The researchers asked the participants how many hours of sleep they got on a typical night of the week. The UCL researchers then categorized sleep as “short” if they slept less than six hours, “optimal” if they slept between six and eight hours and “long” if they slept more than eight hours.
The researchers also asked the participants how much they exercised. Participants reported how often they participated in light, moderate, and vigorous physical activity and whether they exercised more than weekly, once a week, one to three times a month, and rarely/never.
The researchers assessed participants’ episodic memory using the Alzheimer’s Disease Registry Consortium’s immediate and delayed recall tasks. Researchers gave participants a list of ten words and asked them to recall the words immediately and again a day later. The researchers also assessed the participants’ verbal fluency using a task in which participants named as many animals as they could think of in a minute.
The UCL researchers excluded participants who reported being diagnosed with dementia during the follow-up period, as well as participants whose test results indicated some cognitive impairment. In addition, the researchers adjusted their analyzes for a number of factors, such as whether participants had previously taken the same cognitive test.
Of the 3,069 participants the researchers placed in the “higher physical activity category,” 1,525 participants (50%) reported engaging in light, moderate, or vigorous exercise more than weekly. Another 1161 participants (37.8%) reported doing light to moderate exercise more than a week and vigorous exercise once a month or once a week.
Among the 5889 participants in the category of low physical activity, 2384 participants (40.5%) stated that they do not engage in intense physical activity, but more than a week of light and moderate physical activity. Another 1,511 participants (25.7%) stated that they engage in light physical activity more than once a week, moderate physical activity weekly or less often, and no intense physical activity.
Participants who engaged in more physical activity were more likely to sleep 6-8 hours a night. They were also more likely at baseline to be younger, male, married or partnered, and to have more education and wealth than those in the lower physical activity group. Those in the higher physical activity group were more likely to not smoke, had a lower body mass index (BMI)fewer diagnoses of all chronic conditions and less depressing symptoms compared to those in the lower physical activity group.
Participants in the higher physical activity group generally had the highest baseline cognitive scores regardless of how long they slept.
“(H)owever, at ages 50 and 60, those with greater physical activity and short sleep declined more rapidly such that after 10 years of follow-up they had cognitive outcomes similar to those in the less physically active groups,” UCL researchers they write in their paper about the study.
“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 consistent with previous research indicating the important role of sleep in cognitive and physical recovery.”
– Dr. Bloomberg
Among older participants (aged 70 and older), the cognitive benefits of exercise were maintained even among people who slept poorly.
Dr. Vernon Williamssports neurologist, pain specialist and founding director of the Center for Sports Neurology and Pain Medicine at the Cedars-Sinai Kerlan-Jobe Institute in Los Angeles, told MNT that he appreciates the data on the importance of sleep for long-term cognitive benefits.
“The concept that both exercise and sleep are critical factors in maintaining cognitive health coupled with evidence that maintaining physical health in the absence of optimal sleep health reduces the cognitive benefits of physical activity is compelling,” said Dr. Williams.
Ryan Glattsenior brain health coach and director of the FitBrain program at the Pacific Neuroscience Institute in Santa Monica, CA, said MNT he found the study “very interesting” but noted limitations.
“(T)here are potential problems with the accuracy of self-reported physical activity and sleep duration, and potential presence sleep disorders or the effects of certain medications were not taken into account,” Glatt said.
dr. Bloomberg believes there may be a way to conduct this research that doesn’t rely on the truthfulness of the participants.
“An interesting next step would be to use objective measures of sleep and physical activity—for example, using wrist-worn accelerometers—to see if we observe similar results,” she said. MNT.
In the future, the UCL researchers would also like to see a similar study carried out on a more diverse population. Additionally, Dr. Bloomberg said MNT she would like to “extend the results to dementia”.
“We deliberately excluded those with dementia and those with cognitive scores suggestive of cognitive impairment, to increase the likelihood that we were capturing the effects of sleep on cognitive function, rather than the other way around,” said Dr. Bloomberg. “Future research should (examine) how combinations of physical activity and sleep affect (the) risk of dementia.”