# Longitudinal Associations Between Physical Activity Behavior and Structural Brain MRI Features After Stroke: A Sub-Study From the Nor-COAST Project

## TL;DR

This study shows that higher physical activity after a stroke is linked to better brain structure and younger brain age estimates.

## Contribution

The study identifies specific associations between post-stroke physical activity and structural brain MRI features over time.

## Key findings

- Every 1000 additional steps/day were linked to lower brain age gap and larger cortical and hippocampal volumes.
- The most active participants had significantly lower brain age gap and larger thalamic volumes compared to the least active.
- Thalamic volume showed a curvilinear relationship with step count, peaking at 4700 steps/day.

## Abstract

Post-stroke physical activity (PA) behavior may partly explain inter-individual differences in cortical and sub-cortical brain volumes and brain age estimates.

To investigate longitudinal associations of post-stroke PA behavior with structural brain MRI features.

Data were from a multicenter longitudinal cohort study. PA estimates were based on accelerometer measurements. Separate linear mixed models assessed average daily step count at 18 and 36 months, and longitudinal PA trajectory groups as measured at 3, 18, and 36 months after stroke, as primary and secondary exposures. Dependent variables included brain age gap (BAG), representing the discrepancy between brain MRI predicted age and chronological age, and MRI-based cortical, hippocampal, and thalamic volumes at 18- and 36 months post-stroke. Models accounted for age, sex, education, stroke severity, intracranial volume, and MRI scanner.

We included 146 participants (age, mean [SD]: 70.3 [11.1]; 45.7% female) with predominantly mild strokes. Every +1000 steps/day were associated with −1.15 (95% CI: −1.76 to −0.53) lower BAG, 2.63 mL (95% CI: 0.31-5.00) larger cortical volume, and 0.07 mL (95% CI: 0.03-0.11) larger hippocampal volume. The association between step/day and thalamic volume was curvilinear, with the largest volumes observed at 4700 steps/day. Out of 4 PA trajectory groups, participants in the most active group had −7.44 years (95% CI: −2.86 to −12.01) lower BAG and 0.90 mL (95% CI: 1.48-0.33) larger thalamic volumes than the least active group.

Higher PA levels post-stroke were associated with larger brain volumes and younger-appearing brains.

Graphical Abstract