Overview: Frequent moderate to vigorous exercise is linked to better cognition and brain power in middle age. This level of intensity was associated with better working memory and mental processes. Reducing intensity to a lower intensity or sedentary behavior for 6-7 minutes per day was associated with poorer cognitive performance.
The amount of time spent in moderate and vigorous physical activity each day is associated with midlife brain power, according to research published online in the Journal of Epidemiology & Community Health.
This level of intensity appears to be best for working memory and mental processes such as planning and organization, and replacing it with just 6-7 minutes of light intensity activity or sedentary behavior per day is associated with poorer cognitive performance, the findings show.
Previously published studies link daily moderate and vigorous physical activity, or MVPA for short, to health, but few have included sleep time, which makes up the largest component of any 24-hour period, the researchers say.
They therefore took a compositional approach to find out whether MVPA might be best for midlife cognitive performance relative to all other daily exercise behaviors.
They were based on participants in the 1970 British Cohort Study, which consisted of people born in England, Scotland and Wales in 1970 and whose health was followed through childhood and adulthood.
In 2016-2018, 8581 participants had reached the age of 46-47. At that point, they were asked to complete detailed health, background and lifestyle questionnaires and to wear an activity tracker for up to 7 days and for at least 10 days. consecutive hours per day.
They took several cognitive tests for verbal memory (immediate and delayed word recall) and executive functions (verbal fluency and processing speed/accuracy).
Scores for each test were added together to produce an overall global score for memory and executive function.
Of those who agreed to wear an activity tracker, 2959 participants were excluded due to device errors, insufficient wearing time or not completing the questionnaires completely.
The final analysis included 4481 participants, of whom just over half (52%) were female. Two-thirds (66%) were married and 43% had completed education up to the age of 18. Over two-thirds (68%) were occasional or non-risk drinkers and half had never smoked.
Analysis of the activity tracker data showed that participants clocked an average of 51 minutes of MVPA, 5 hours and 42 minutes of light-intensity physical activity, 9 hours and 16 minutes of sedentary behavior, and 8 hours and 11 minutes of sleep over a 24-hour period .
Time spent in MVPA relative to other types of behavior was positively associated with cognitive performance after adjusting for education level and physical activity at the workplace. But additional adjustment for health problems weakened these associations.
Sedentary behavior over sleep and light physical activity was also positively associated with cognitive performance: a trend that likely reflects more engagement in cognitively stimulating activities such as reading or working than any clear benefit from watching TV, the researchers note.
The associations were stronger for executive function than for memory.
Compared to the sample mean, participants in the top half of the cognitive performance scores spent more time in MVPA and sedentary behaviors and less time sleeping, while the bottom 25% of scorers clocked the lightest physical activity.
To better understand the joint associations of movement with cognition, the researchers moved time from one component to another, minute by minute, to estimate what impact this might have on global cognitive performance scores.
This revealed increases in scores after MVPA theoretically supplanted other activities.
Individuals’ cognition showed a 1.31% improvement in cognition ranking compared to the mean sample improvement after just 9 minutes of sedentary activity with more vigorous activity – a positive trend that became much more substantial with much greater reductions in sedentary activity.
Similarly, there was a 1.27% improvement by replacing quiet activities or 1.2% by replacing 7 minutes of sleep. Such improvements showed further improvement with more exchange of time.
Sedentary behavior was also beneficial for cognition score, but only after replacing it with 37 minutes of light-intensity physical activity or 56 minutes of sleep.
Participants theoretically began to decline by 1-2% in their cognition rankings within the study sample after replacing just 8 minutes of more vigorous activity with sedentary activity. The rankings continued to fall with larger drops in MVPA.
Similarly, replacing vigorous activity with 6 minutes of light-intensity physical activity or 7 minutes of sleep was associated with similar 1–2% declines in cognition ranking, again worsening for greater losses of MVPA.
The activity trackers can only record time spent in bed rather than sleep duration or quality, which could help explain the association with sleep, the researchers say.
“MVPA is typically the shortest part of the day in real terms, and the most difficult intensity to acquire. Perhaps partly for this reason, the loss of any MVPA time seemed detrimental, even within this relatively active cohort,” they explain.
This is an observational study and as such cannot establish a cause. And the researchers point out several caveats: Activity tracker measures can’t provide context for every part of movement. And despite a large sample size, people of color were underrepresented, limiting the generalizability of the findings.
Nevertheless, they conclude, “This robust method confirms a critical role for MVPA in supporting cognition, and efforts should be made to reinforce this component of daily movement.”
About this research into movement, aging and cognition
Writer: Press Office
Contact: Press Service – BMJ
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Original research: Open access.
“Exploring the Associations of Daily Movement Behavior and Midlife Cognition: A Composite Analysis of the 1970 British Cohort Study” by John J Mitchell et al. Journal of Epidemiology & Community Health
Investigating the associations of daily exercise behavior and midlife cognition: a composite analysis of the 1970 British Cohort Study
Exercise behaviors (e.g., sedentary behavior (SB), moderate and vigorous physical activity (MVPA), light-intensity physical activity (LIPA), and sleep) are linked to cognition, but the relative importance of each component is unclear and not yet explored with compositional methodologies .
To (i) assess the associations of various components of daily movement and the participant’s overall cognition, memory, and executive function, and (ii) understand the relative importance of each individual component to cognition.
The 1970 UK Cohort Study (BCS70) is a prospective birth cohort study of UK-born adults. At age 46, the participants agreed to wear an accelerometer and take tests of verbal memory and executive function. Compound linear regression was used to examine cross-sectional associations between 24-h exercise behavior and standardized cognition scores. Isotemporal substitution was performed to model the effect of time reallocation between components of daily movement on cognition.
The sample consisted of 4481 participants (52% female). Time in MVPA relative to SB, LIPA, and sleep was positively associated with cognition after adjusting for education and occupational physical activity, but additional adjustment for health status attenuated associations. SB relative to all other movements was robustly positively associated with cognition. Modeling time redistribution between components revealed an increase in cognition centile after theoretical MVPA 9 minutes SB (OR = 1.31; 95% CI 0.09 to 2.50), 7 minutes LIPA (1.27, 0.07 to 2, 46) or replaced 7 minutes of sleep (1.20); 0.01 to 2.39).
Relative to time spent on other behaviors, more MVPA and SB was associated with higher cognitive scores. Loss of MVPA time, given the smaller relative amount, appears highly detrimental. Efforts should be made to maintain or reinforce MVPA time rather than other behaviors.