- Researchers looked at cognitive function over 10 years in 8,958 people
aged 50 and older in England.
- The study found people who slept between 6 and 8 hours per night and engaged
in higher levels of physical activity were linked with better cognitive function.
- People who slept fewer than 6 hours a night, even if they engaged in higher
levels of physical activity, experienced more rapid 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 suggests that physical activities are beneficial
to brain health and may protect against the development of neurodegenerative
conditions such as
Parkinson’s disease. However, a new study found that
sleep deprivation can reduce such benefits reaped from exercise.
Almost 10% of adults age 65 and older in the United States have dementia,
and another 22% have
mild cognitive impairment, according to a 2022 nationally representative
study of cognitive impairment prevalence.
studies have found exercise may reduce the risk of developing dementia. Still,
more studies link a
lack of sleep with increased dementia risk.
“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
Mikaela Bloomberg, Ph.D., a research fellow at the University College London Institute of Epidemiology
and Health Care, explained to
Medical News Today.
A team of UCL researchers, including Bloomberg, found little existing research
that looked at the impact of physical activity
and sleep on cognitive function. The studies they found were small and
cross-sectional, which is a type of research where researchers collect data from participants
at a single point in time.
“Because sleep disturbances can be an early symptom of neurocognitive
diseases like dementia, which cause cognitive dysfunction, it is challenging
to determine whether the results we observe in those previous studies
are due to the effects of sleep on cognitive function or vice versa,”
Dr. Bloomberg said. “With this in mind, we wanted to examine how
combinations of physical activity and
sleep habits influenced cognitive function over a long period of time.”
A paper by the UCL researchers on their large-scale, longitudinal study
The Lancet Healthy Longevity
For their study, UCL researchers used longitudinal data on 8,958 cognitively
healthy adults from England aged 50 and older taken from the
English Longitudinal Study of Ageing (ELSA). The data used was collected between Jan. 1, 2008, and July 31, 2019.
Participants gave reports about their physical activity and sleep duration
every two years.
Researchers asked participants how many hours they slept on a typical weeknight.
The UCL researchers then categorized sleep as “short” if it
was less than six hours, “optimal” if between six and eight
hours, and “long” if more than eight hours were received.
Researchers also asked participants how much they exercised. Participants
reported how frequently they participated in light, moderate, and vigorous
physical activity and whether they exercised more than weekly, weekly,
one to three times a month, and rarely/never.
Researchers assessed the episodic memory of participants using the Consortium
to Establish a Registry for Alzheimer’s disease immediate and delayed
recall tasks. Researchers gave participants a ten-word list and asked
them to recall the words immediately and again a day later. Researchers
also assessed the participants’ verbal fluency using a task where
the participants named as many animals as they could think of over the
course of a minute.
The UCL researchers excluded participants who reported being diagnosed
with dementia during the follow-up period as well as participants whose
test scores suggested some cognitive impairment. Additionally, researchers
adjusted their analyses for a number of factors, such as whether participants
had taken the same cognitive test previously.
Of the 3,069 participants who researchers placed in the “higher physical
activity category,” 1,525 participants (50%) reported engaging in
light, moderate, and vigorous exercise more than weekly. Another 1,161
participants (37.8%) reported engaging in light and moderate exercise
more than weekly and vigorous exercise monthly or weekly.
Among the 5,889 participants in the lower physical activity category, 2,384
participants (40.5%) reported engaging in no vigorous physical activity
but more than weekly light and moderate physical activity. Another 1,511
participants (25.7%) reported engaging in more than weekly light physical
activity, moderate physical activity weekly or less often, and no vigorous
Participants who engaged in higher physical activity were more likely to
sleep 6–8 hours a night. They were also more likely to be younger
at baseline, male, married, or had a partner, and had more education and
wealth than those in the lower physical activity group. Those in the higher
physical activity group were more likely not to smoke, had lower
body mass indexes (BMI), fewer diagnoses of all chronic conditions, and fewer
depressive symptoms compared with those in the lower physical activity group.
Participants from the higher physical activity group generally had the
highest baseline cognitive scores regardless of how long they slept.
“[H]owever, 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 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 in line with previous
research pointing to an important role of sleep in cognitive and physical
– Dr. Bloomberg
Among older participants (age 70 and above) the cognitive benefits of exercise
appeared to be maintained even among poor sleepers.
Dr. Vernon Williams, sports neurologist, pain management specialist, and founding director
of the Center for Sports Neurology and Pain Medicine at Cedars-Sinai Kerlan-Jobe
Institute in Los Angeles, told MNT he appreciated seeing data about the
importance of sleep for long-term benefits regarding cognitive function.
“The concept that both exercise AND sleep are critical factors for
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,” Dr. Williams said.
Ryan Glatt, a senior brain health coach and director of the FitBrain Program at the
Pacific Neuroscience Institute in Santa Monica, CA, told
MNT he found the study “very interesting” but noted limitations.
“[T]here are potential issues with the accuracy of self-reported
physical activity and sleep duration, and the potential presence of
sleep disorders or the effects of certain medications were not considered,” Glatt said.
Dr. Bloomberg believes there may be a way to conduct this research that
doesn’t rely on participants’ truthfulness.
“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 told
In the future, the UCL researchers would also like to see a similar study
performed on more diverse populations. Additionally, Dr. Bloomberg told
MNT she’d like “to extend the results to dementia.”
“We purposefully excluded those with dementia and those with cognitive
scores that suggested cognitive impairment, in order to make it more likely
that we were capturing the effects of sleep on cognitive function and
not vice versa,” Dr. Bloomberg said. “Future research should
[examine] how combinations of physical activity and sleep impact [the]
risk of dementia.”