Sitting may not always be bad for the brain and, in fact, may benefit cognition, new research suggests.
Although physical activity in seniors is beneficial for overall health, the new study suggests that being sedentary may benefit certain cognitive capacities, as long people are also sufficiently physically active.
Investigators found that daily moderate-to-vigorous physical activity was associated with better fluid abilities, including perceptual speed and reasoning, while more sedentary time was associated with better performance on tests of vocabulary knowledge as well as reasoning.
“I don’t think I would in any way suggest that we should engage in more sitting, but I think trying to be as physically active as possible and making sure that you get stimulated in your sedentary time — that it’s not just spent starting at the TV — that this combination might be the best way to take care of your brain,” lead author Aga Burzynska, PhD, assistant professor, Colorado State University Department of Human Development and Family Studies, said in a release.
The study was published online September 24 in Psychology and Aging.
Fluid abilities such as processing speed and memory, problem solving, and reasoning tend to decline as people age. On the other hand, “crystallized” abilities — particularly vocabulary — tend to improve, possibly because people acquire more knowledge and experience as they move through adulthood.
A question of interest is the impact of sedentary time on cognition, as increased physical activity and reduced sedentary time are recommended to improve a variety of health conditions, study coauthor Jason Fanning, PhD, assistant professor and Wells Fargo Faculty Scholar, Department of Health and Exercise Science, and internal medicine, Wake Forest University, Winston-Salem, North Carolina, told Medscape Medical News.
There has been increased interest in the study of sedentary time during the past 2 decades, he said. “This is partially related to how many of us spend much of our waking time seated on the couch, at a desk, or in the car.”
However, Fanning added, researchers have also “acknowledged that there are many forms of sedentary behavior, such as socializing, watching TV, or working on puzzles, that may benefit aspects of cognition.”
This increased interest has also been “driven by wider use of sensors that can help objectively measure sitting and physical activity.”
Burzynska noted that individuals tend to overestimate their daily movement and underestimate the time they spend sitting, so “a key aspect of this study was to measure lifestyle [physical activity] using sensors, not self-reports, [which were used in previous studies] allowing for a more objective estimate of daily activity, especially low-intensity activity.”
The researchers focused on baseline data from a previous 6-month trial of an aerobic activity intervention for older adults aged 60 to 80 years. Participants (n = 228; 68% female) were required to be right-handed, have no history of neurological or psychiatric illness, and be cognitively intact, based on the Mini-Mental State Examination and the Mental State Questionnaire.
Participants wore a sensor device on their nondominant hip during waking hours for 7 consecutive days. Data were downloaded as “activity counts” and were categorized as:
|≤ 50 counts/minute|
|Light PA||51 – 1040 counts/minute|
|Moderate-to-vigorous PA||≥ 1041 counts/minute|
|PA = Physical activity|
“Light” physical activity included activities such as doing laundry, cooking, or other household chores.
“Current cognitive activities” were based on participation in adult education classes, employment status, and comfort using a computer, as a proxy of time and skill.
The researchers also looked at socioeconomic and health factors, including general health status, diabetes mellitus, mean arterial pressure, education, income level, and employment status.
After adjusting for age, sex, adult education, and both types of physical activity, sedentary behavior was associated with greater vocabulary knowledge (P < .001), although the effect size was small.
Moderate-to-vigorous physical activity was associated with faster perceptual speed (P < .001). Younger age, female sex, being employed, having greater comfort at the computer, and greater mean arterial pressure were also associated with faster perceptual speed, but effect sizes were small.
Time spent in sedentary behavior and moderate-to-vigorous physical activity were associated with better reasoning, a cognitive ability included in both the fluid and crystallized categories (P < .001).
Comfort at a computer and cardiorespiratory fitness were also positively associated with reasoning, albeit with small effect sizes. Time spent engaging in light physical activity was not associated with either fluid or crystallized abilities.
The researchers noted that it would be “tempting to speculate that the time spent being sedentary was related to engaging in cognitively stimulating sedentary activities,” but a “bidirectional or third variable relationship is equally plausible.”
“One important next step will be pairing objective sensor data, as we reported here, with reports on the type of sedentary behavior people are engaging in,” Fanning said.
Physical Activity Remains Important
Commenting on the study for Medscape Medical News, Madeleine Hackney, PhD, associate professor of medicine, Emory School of Medicine, Division of General Medicine and Geriatrics, Atlanta, Georgia, said it was interesting that the study results suggest time spent being sedentary was deemed “okay.” However, she added, they also suggest that individuals were engaging in cognitive activities that contribute to brain health.
Hackney, who is also a research scientist at the Atlanta VA, and was not involved with the study, called the finding that light physical activity had no impact on cognition “disheartening,” emphasizing that it still “is a great action for our seniors and has benefit, although maybe not for fluid cognition in particular.”
Also commenting on the study for Medscape Medical News, Douglas Scharre, MD, director of the Division of Cognitive Neurology, Ohio State University Wexner Medical Center in Columbus, said that individuals with cognitive disorders and dementia who engage in higher levels of physical activity seem to experience slower cognitive decline vs their sedentary counterparts.
“My usual suggestions are to increase physical activity [and] increase socialization [as people are] now socially distanced, and increase other brain stimulation activities,” stated Scharre, who was not involved in the research.
This work was supported by the National Institute on Aging and by a grant from the National Institutes of Health, as well as funding from Abbott Nutrition through the Center for Nutrition, Learning, and Memory at the University of Illinois. The authors, Hackney, and Scharre report no relevant financial relationships.
Psychol Aging. Published online September 24, 2020. Abstract