Exercise

Of all the lifestyle factors that protect the aging brain, exercise has the strongest and most consistent evidence behind it. Regular physical activity — particularly aerobic exercise — reduces the risk of cognitive decline and dementia, improves memory and executive function, and produces measurable structural changes in the brain itself. The 2020 Lancet Commission on Dementia Prevention identified physical inactivity as one of 12 modifiable risk factors collectively responsible for approximately 40% of dementia cases worldwide, and the 2024 update raised that estimate to 45% with the addition of two further risk factors. You don't have to train for a marathon. The research is clear that meaningful benefits begin with modest, consistent activity — and that going from doing nothing to doing something produces the largest gains.

One of the most compelling findings in this area came from a landmark randomized controlled trial by Erickson and colleagues, published in the Proceedings of the National Academy of Sciences in 2011. In that study, 120 older adults were randomly assigned to either aerobic exercise (walking) or a stretching control condition for one year. The aerobic exercise group showed a 2% increase in hippocampal volume — the brain's primary memory center — effectively reversing approximately one to two years of age-related hippocampal shrinkage. The control group showed the expected decline. These structural brain changes were accompanied by improvements in spatial memory and increases in brain-derived neurotrophic factor (BDNF), a protein that supports the growth and survival of neurons. This study demonstrated that the aging brain remains physically responsive to exercise — and that it's never too late to start.

More recent meta-analyses have confirmed and extended these findings across different types of exercise and cognitive outcomes. A 2024 network meta-analysis found that both aerobic exercise and mind-body exercise (such as tai chi and yoga) significantly enhanced memory in older adults, with the greatest effects from moderate-intensity, moderate-duration programs practiced several times per week. The neurobiological mechanisms include increased hippocampal neurogenesis, improved cerebrovascular blood flow, reduced chronic neuroinflammation, and elevated levels of BDNF and IGF-1. Resistance training has also shown independent benefits for executive function and processing speed. The current evidence supports a combined approach — aerobic activity for memory and hippocampal health, resistance training for executive function and overall brain reserve — at a minimum of 150 minutes of moderate-intensity activity per week, consistent with standard public health guidelines.

Want to go deeper? Module 5 of the Brain Health for Life course — Exercise & the Brain — covers the full evidence base, explains the mechanisms in plain language, and helps you build a personalized exercise plan that fits your life. You'll learn how much exercise is enough, which types of activity have the strongest evidence for brain protection, and practical strategies for getting started and staying consistent.

Erickson, K.I., Voss, M.W., Prakash, R.S., et al. (2011). Exercise training increases size of hippocampus and improves memory. Proceedings of the National Academy of Sciences, 108(7), 3017–3022.
https://doi.org/10.1073/pnas.1015950108

Livingston, G., Huntley, J., Sommerlad, A., et al. (2020). Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. The Lancet, 396(10248), 413–446.
https://doi.org/10.1016/S0140-6736(20)30367-6

Livingston, G., Huntley, J., Liu, K.Y., et al. (2024). Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet, 404(10452), 572–628.
https://doi.org/10.1016/S0140-6736(24)01296-0

Huang, X., Zhao, X., Li, B., et al. (2025). Optimal exercise interventions for enhancing cognitive function in older adults: a network meta-analysis. Frontiers in Aging Neuroscience.
https://pmc.ncbi.nlm.nih.gov/articles/PMC12289702/