Not Just for Joints: Physical Activity is Associated with Greater Cortical Thickness among Adults with Osteoarthritis

Abstract

PURPOSE: Preliminary evidence suggests osteoarthritis (OA) is a risk factor for dementia. One potential reason is 87% of adults with OA are inactive, and low moderate-to-vigorous physical activity (MVPA) and high sedentary behaviour (SB) are each risk factors for brain atrophy. While regular MVPA and low SB are thus critical for brain health, it is unclear 1) what aspects of brain structure are associated with these behaviours among adults with OA; and 2) whether the relationships of MVPA and SB with brain structure are independent of each other. Hence, we investigated the independent relationships of MVPA and SB with brain structure in adults with knee OA. METHODS: This was a secondary cross-sectional analysis of a six month, proof-of-concept randomized controlled trial (RCT) to promote MVPA and reduce SB among adults with knee OA. At study entry, we objectively measured MVPA and SB for 7 days using the SenseWear Mini. Following this observation period, participants (N= 30) underwent a 3T magnetic resonance image (MRI) scan, wherein T1-weighted structural MRIs were performed to measure cortical thickness. We performed regression analyses using a surface-based cluster size exclusion method for multiple comparisons within the FreeSurfer neuroimaging software to determine if 1) MVPA was associated with greater cortical thickness independent of SB; and 2) SB was associated with less cortical thickness independent of MVPA. RESULTS: Participants had a mean age of 61 years (SD= 9 years), and 80% were female. Higher MVPA was associated with greater cortical thickness in the temporal pole (cluster size= 855 mm2; p< 0.05) and superior frontal area (cluster size= 1204 mm2; p< 0.05) of the left hemisphere independent of SB. SB was not associated with greater cortical thickness in any region independent of MVPA. CONCLUSIONS: Higher MVPA is associated with greater cortical thickness in adults with OA, however SB does not appear to be strongly associated with brain structure. Promoting MVPA among adults with OA may thus be an important strategy for maintaining cognitive health among this population.