Objectives Examine the effect of aerobic exercise on structural brain age and explore potential mediators.

Methods In a single-blind, 12-month randomized clinical trial, 130 healthy participants aged 26-58 years were randomized into a moderator-to-vigorous intensity aerobic exercise group or a usual-care control group. The exercise group attended 2 supervised 60-minute sessions per week in a laboratory setting plus home-based exercise to achieve 150 minutes of exercise per week. Brain-predicted age difference (brain-PAD) and cardiorespiratory fitness (CRF) were assessed at baseline and 12 months. Intention-to-treat (ITT) and completers analyses were performed.

Results The 130 participants (67.7% female) had a mean (SD) age of 41.28 (9.93) years. At baseline, higher CRF (VO2peak) was associated with smaller brain-PAD (β=-0.309, p=0.012). After the intervention, the exercise group showed a decrease in brain-PAD (estimated mean difference (EMD) =-0.60; 95% CI: -1.15 to -0.04; p=0.034) compared to the control group (EMD=0.35; 95% CI: -0.21 to 0.92; p=0.22); time×group interaction (between-group difference (BGD)= -0.95; 95% CI: -1.72 to -0.17; p=0.019). VO2peak improved in the exercise group (EMD=1.60; 95% CI: 0.29 to 2.90; p=0.017) compared to the control group (EMD=-0.78; 95% CI: -2.17 to 0.60; p=0.26); time×group interaction (BGD=2.38; 95% CI: 0.52 to 4.25; p=0.015). Body composition, blood pressure, and brain-derived neurotrophic factor levels were unaffected. None of the proposed pathways statistically mediated the effect of exercise on brain-PAD. The results from completers were similar.

Conclusion Engaging in 12 months of moderate-to-vigorous exercise reduced brain-PAD in early-to-midlife adults. The pathways by which these effects occur remain unknown.

What is already known on this topic Midlife risk factors influence brain aging, with physical activity conferring protective benefits, yet evidence for the effect of exercise on midlife brain age and underlying mechanisms remains limited.

What this study adds Participation in a 12-month aerobic exercise intervention significantly reduced a neuroimaging marker of brain age. Higher cardiorespiratory fitness was also associated with younger brain age.

How this study might affect research, practice or policy Findings of this study complement the scarce literature examining the effects of exercise on early-to-midlife brain health and confirm the neuroprotective effects of aerobic exercise against accelerated brain aging in early-to-midlife adults.

The authors declare no conflicts of interest relevant to this article. Dr. Erickson is a scientific advisor for MedRhythms, Inc. and Neo Auvra, Inc.

NCT03841669

https://bmjopen.bmj.com/content/13/11/e077905

This study was funded by the National Institutes of Health and the National Heart, Lung, and Blood Institute (P01 HL040962).

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The University of Pittsburgh Institutional Review Board (IRB ID: 19020218) gave ethical approval for this work.

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