Real cognitive change
There was a 1.31% improvement in cognition ranking compared to the sample average after replacing 9 minutes of sedentary activity with MVPA (1.31; 95% confidence interval [CI], 0.09-2.50). There was a 1.27% improvement after replacing 7 minutes of LIPA with MVPA, and a 1.2% improvement after replacing 7 minutes of sleep with MVPA.
Individuals might move up from about the 50th percentile to the 51st or 52nd percentile after just 9 minutes of more moderate to vigorous movement in place of sitting, said Mr. Mitchell. “This highlights how even very modest differences in people’s daily movement – less than 10 minutes – is linked to quite real changes in our cognitive health.”
The impact of physical activity appeared greatest on working memory and mental processes, such as planning and organization.
On the other hand, cognition declined by 1%-2% after replacing MVPA with 8 minutes of SB, 6 minutes of LIPA, or 7 minutes of sleep.
The activity tracking device couldn’t determine how well participants slept, which is “a clear limitation” of the study, said Mr. Mitchell. “We have to be cautious when trying to interpret our findings surrounding sleep.”
Another limitation is that despite a large sample size, people of color were underrepresented, limiting the generalizability of the findings. As well, other healthy pursuits – for example, reading – might have contributed to improved cognition.
In a comment, Jennifer J. Heisz, PhD, associate professor and Canada research chair in brain health and aging, department of kinesiology, McMaster University, Hamilton, Ont., said the findings from the study are important.
“Through the statistical modelling, the authors demonstrate that swapping just 9 minutes of sedentary behavior with moderate to vigorous physical activity, such as a brisk walk or bike ride, was associated with an increase in cognition.”
She added that this seemed to be especially true for people who sit while at work.
The findings “confer with the growing consensus” that some exercise is better than none when it comes to brain health, said Dr. Heisz.
“Clinicians should encourage their patients to add a brisk, 10-minute walk to their daily routine and break up prolonged sitting with short movement breaks.”
She noted the study was cross-sectional, “so it is not possible to infer causation.”
The study received funding from the Medical Research Council and the British Heart Foundation. Mr. Mitchell and Dr. Heisz have disclosed no relevant financial relationships.
A version of this article first appeared on.