Abstract MP05: Prospective Associations of Midlife Physical Activity and Sedentary Behavior With Brain Structure: The Cardia Study

Introduction: Strong evidence suggests physical activity may prevent cognitive decline. Less research has explored potential associations of physical activity with brain structure. This is an important research gap given that age related alterations in brain structure are thought to occur prior to signs of cognitive decline. Objective: To determine if accelerometer measured sedentary time (SED), light-intensity physical activity (LPA), and moderate-to-vigorous intensity physical activity (MVPA) at ages 38-50 years are prospectively associated with brain structure. Methods: We studied 562 Black and White men and women enrolled in CARDIA who participated in the 2005-06 exam (baseline) and exams 5 (2010-11) and/or 10 years later (2015-16). SED, LPA, and MVPA were measured by the ActiGraph 7164 accelerometer at baseline. Magnetic resonance imaging (MRI) was used to quantify whole brain, white matter, gray matter, and abnormal tissue volume of white matter at the 5- and/or 10-year follow-up. Compositional isotemporal substitution analysis examined associations of SED, LPA, and MVPA at baseline with repeated measures (unstructured covariance) of MRI measures at follow-up after accounting for intracranial volume and adjusting for confounders ( Table ). Results: Consistent with our hypothesis, substituting 30 minutes of SED to LPA was associated with 0.044% greater total white matter volume (95% CI: 0.001, 0.086). The effect size was larger when substituting SED to MVPA, but this association was not statistically significant. There were no associations observed between accelerometer measures and total brain, total gray matter, or abnormal white matter tissue volumes. Associations did not differ by sex or age. Conclusions: Statistical substitution of time from SED to higher intensity physical activity (LPA or MVPA) was associated with greater total white matter volume. It is unclear why this association was observed in white matter only. Additional research with longer follow-up is needed to confirm these findings.