Researchers publishing in Ageing Research Reviews have conducted a large meta-analysis of papers that document the effects of exercise on cognitive function in healthy people.
Not just for established conditions
We have previously discussed how, even for healthy people, exercise is associated with improved biomarkers of health. These researchers have done something similar, although rather than biological biomarkers, their research focuses on analyzing the effects of exercise on cognition in healthy people.
This meta-analysis was created through a search of studies conducted from January 2003 to April 2022. To be included, each study had to meet four critical criteria: it had to be a randomized, controlled trial rather than a cohort or longitudinal study, it had to include any type of regular exercise, it had to be published in English, and it had to report at least one cognitive outcome.
These studies were carefully analyzed for potential sources of bias, including improper blinding and randomness along with incomplete reporting of information. Of the over 15,000 non-duplicate studies found by the reviewers, only 54, containing 6,277 participants, were found to be suitable for data analysis.
Because all of these studies had different methods of quantifying exercise, they were normalized according to FITT-VP: frequency, intensity, time, type, volume, and progression. These are the fundamental aspects behind medical prescriptions of exercise, detailing what kind of exercise people do and when. What this means in practice varies greatly by the individual: what is ‘moderate’ for one person may be nearly impossible for someone else.
Towards more conclusive results
Interestingly, many of the individual studies found tendencies toward improvements in various domains of brain function, but individually, relatively few of them provided statistically significant results on their own. However, combining them together provided far more useful information.
All exercise types were found to have significant effects on overall cognition, with resistance exercise (lifting and related activities) having the greatest effect. The reviewers also noted that exercises with an aerobic component were less effective than strict resistance-based interventions.
The effects of short exercise sessions were inconclusive, but moderate and longer sessions had positive effects, with moderate being the most effective. However, low-frequency exercise was found to have slightly more significant effects than moderate-frequency exercise for cognition. Moderation was also found to be a good idea for exercise intensity, and interventions that spanned a longer span of time were found to be more effective than shorter-term interventions.
In total, for overall cognition and for executive function, the results of this meta-analysis suggest that a moderate-intensity, moderate-length session of weightlifting conducted at a low frequency is broadly beneficial. Mind-body exercise (such as yoga and tai chi), moderate duration and frequency, and high-intensity exercise were found to be beneficial for memory. Attention and information processing were found to benefit from low-intensity, moderate-frequency exercise, although these domains were less well-studied and had few papers.
A further analysis found that people who were at least 60 years old had, by far, the greatest effects in all of the cognitive domains studied; exercise was found to have far fewer effects on cognition in younger people.
This meta-analysis contains no biological examinations, but the reviewers do note previous research linking such factors as IGF-1  and BDNF  to potential benefits of exercise in older people. As biology changes with age, exercise may be responsible for spurring mechanisms that may not need to be spurred in younger people.
Offering more exercise interventions to less functional older populations may induce more biological mediators to help guard against cognitive decline during aging.
This is a meta-analysis of randomized, controlled trials that were conducted on human beings. Therefore, it provides broad and largely conclusive evidence that regular, infrequent, and moderate exercise, particularly resistance exercise, conducted over a long period of time is likely to help cognitive function in people who are at least 60 years old. However, it specifically refers to exercise prescriptions that professionals gave to individual participants. Someone who is looking to start an exercise regimen to fight cognitive decline may be well-served by consulting a medical expert first.
 Ashpole, N. M., Sanders, J. E., Hodges, E. L., Yan, H., & Sonntag, W. E. (2015). Growth hormone, insulin-like growth factor-1 and the aging brain. Experimental gerontology, 68, 76-81.
 Wrann, C. D., White, J. P., Salogiannnis, J., Laznik-Bogoslavski, D., Wu, J., Ma, D., … & Spiegelman, B. M. (2013). Exercise induces hippocampal BDNF through a PGC-1a/FNDC5 pathway. Cell metabolism, 18(5), 649-659.