LARGER LATERAL PREFRONTAL CORTEX VOLUME PREDICTS BETTER EXERCISE CLASS ATTENDANCE AMONG OLDER ADULTS: EVIDENCE FROM THREE EXERCISE TRAINING STUDIES

Abstract

Engaging in regular exercise has numerous benefits in older adults, including to cognition and brain health. Recent research has suggested an important role of lateral prefrontal cortex (lPFC) in engagement in positive health behaviors, including adhering to exercise. 145 older adults (age range 59-89 years) from 3 previous studies of exercise training who underwent structural MRI prior to starting the exercise training. Cortical segmentation and volume estimation were determined in Freesurfer (version 5.3.0). Depending on the study and treatment condition, exercise consisted of aerobic, resistance, or balance-and-tone training, 1,2, or 3 times per week, and for 6 or 12 months. Exercise adherence was calculated as the percentage of exercise classes attended during the exercise-training period. Robust mixed-model regression, including study as a random effect, determined whether baseline lPFC volume predicted exercise adherence. Across the three studies, average exercise adherence was 66% (range 0%-100%) and average baseline lPFC volume was 68.2cm3 (range 43cm3-86cm3). Independent of baseline intracranial volume, age, and treatment condition, larger lPFC volume predicted greater exercise adherence, such that each 1cm3 increase in lPFC volume was associated with a 0.6-percentage point increase in exercise adherence (95% CI: 0.1-1.1). Regional analysis showed that this relationship was driven by volume in the middle frontal gyrus (0.9, 95% CI:0.1-1.6) and in the lateral orbito-frontal cortex (3.0, 95% CI:0.6-5.4), but not in the inferior frontal gyrus (1.5, 95% CI: -0.1, 3.2). See Figure for scatterplots of these associations.