Physically active individuals who had fewer than 6 hours of sleep showed faster cognitive decline overall.
Although physical activity may lessen cognitive decline with age, the effect could be diminished for individuals who are not getting adequate sleep, according to results of a study by the University College of London (UCL).
Investigators found that individuals who were physically active but had fewer than 6 hours of sleep, on average, had faster cognitive decline overall. After 10 years, the cognitive function among these individuals was equivalent to those who did less physical activity.
“Our study suggests that getting sufficient sleep may be required for us to get the full cognitive benefits of physical activity. It shows how important it is to consider sleep and physical activity together when thinking about cognitive health,” Mikaela Bloomberg, PhD, from UCL’s Institute of Epidemiology and Health Care, said in a statement. “Previous studies examining how sleep and physical activity might combine to affect cognitive function have primarily been cross-sectional, only focusing on a snapshot in time, and we were surprised that regular physical activity may not always be sufficient to counter the long-term effects of lack of sleep on cognitive health.”
Investigators included more than 10 years of data for 8958 individuals aged 50 years and older from England. The researchers sought to determine how different combinations of sleep and physical activity affect an individual’s cognitive function over time.
Individuals in the study were asked how long they slept on an average weeknight. Investigators then split the individuals into 3 sleep groups of fewer than 6 hours (short), 6 to 8 hours (optimal), and greater than 8 hours (long).
Additionally, investigators scored the individuals based on the frequency and intensity of their self-reported physical activity. Patients were divided into 2 groups: more physically active (the top third of scorers) and less physically active (the other two-thirds).
Cognitive function was assessed on episodic memory, with the individuals recalling a 10-word list, both immediately and after a delay, and verbal fluency test in which the individuals named as many animals as they can in 1 minute. The results showed that sleeping between 6 and 8 hours per night with higher levels of physical activity are linked with better cognitive function, which was similar to previous research.
Additionally, those who were more physically active had better cognitive function, regardless of how long they slept at the beginning of the study. However, over the 10-year period, investigators found that more physical activity and fewer than 6 hours of sleep were linked with more rapid cognitive decline. This result was observed among those who were in their 50s or 60s; however, individuals aged 70 years and older maintained the cognitive benefit from physical activity, regardless of how long they slept.
“It is important to identify the factors that can protect cognitive function in middle and later life as they can serve to prolong our cognitively healthy years and, for some [individuals], delay a dementia diagnosis,” Andrew Steptoe from the UCL’s Institute of Epidemiology and Health Care, said in the statement. “The World Health Organization already identifies physical activity as a way to maintain cognitive function, but interventions should also consider sleep habits to maximize long-term benefits for cognitive health.”
The findings were published in The Lancet Healthy Longevity.
Lack of sleep lessens cognitive benefits of physical activity. News release. EurekAlert. July 5, 2023. Accessed July 7, 2023. https://www.eurekalert.org/news-releases/994546