A cross-sectional subset of the Long-term Outcome Ankylosing Spondylitis (LOAS) cohort included 141 people with physician-confirmed radiographic axial spondyloarthritis. The mean age was 60 years and mean diagnostic duration was 25 years; 57% were male. Fifty-six percent were managed in specialist rheumatology care and 42% were on disease-modifying antirheumatic drugs. According to ASDAS, 56% had inactive disease or low disease activity (<2.1). Health status was measured with ASAS HI and HRQoL with the SF36 physical and mental component summaries.
Investigators assessed physical function with the Bath Ankylosing Spondylitis Functional Index (BASFI), spinal mobility using the modified BASMI, leg strength by the Timed Stands Test (TST), and handgrip force with Grippit. Physical activity was self-reported across three domains: vigorous activity (exercise making you short of breath and sweaty), moderate activity (brisk walks, gardening, cycling), and sedentary behavior (sitting, apart from sleep). ASAS HI scores were categorized with ≤5 indicating good health, >5–<12 moderate, and ≥12 poor health.
Multivariable linear regression models included age, BASFI, BASMI, TST, Grippit, vigorous physical activity, moderate physical activity, and sedentary behavior. The study team reported that physical function (BASFI) and vigorous physical activity were the strongest independent determinants of both ASAS HI and the SF36 physical component (PCS) in the overall cohort. The models accounted for roughly 51% of the variation in ASAS HI and about 48% of the variation in SF36-PCS. For the SF36 mental component (MCS), the model explained approximately 21% of observed variation.
Univariate correlations matched the multivariable results: BASFI showed strong correlation with ASAS HI (Spearman rho ~0.69) and with SF36-PCS (rho ~−0.66). BASMI, TST, Grippit, and vigorous activity demonstrated weak-to-moderate correlations with ASAS HI and SF36-PCS. Age correlated with reduced spinal mobility and muscle strength.
When participants were compared with published reference values adjusted for age and sex, 55% fell within the BASFI cutoff values considered comparable to general-population levels, and 45% had BASMI within the normal range. Muscle tests showed higher concordance with references: 82% performed within normal range for leg strength (TST) and 91% for handgrip (Grippit). Self-reported activity distribution showed 51% engaged in more than one hour per week of vigorous activity. Using WHO thresholds, 77% met recommended levels for health-enhancing physical activity.
Stratified models revealed sex differences in which objective muscle measures associated with health outcomes. In men, greater leg strength (better TST) contributed to better ASAS HI. In women, greater handgrip force (Grippit) associated with better ASAS HI. For SF36-PCS, both sexes showed associations with BASFI and vigorous activity, but moderate activity additionally associated with PCS among women. For SF36-MCS, younger age, better BASFI, and higher vigorous activity related to better mental HRQoL in women; in men only BASFI was independently associated. The models explained more of the variance for outcomes in females for mental health (35%) than in males (8%).
This analysis is cross-sectional; therefore the source did not report causal relationships or longitudinal effects of changes in physical activity. Physical activity was self-reported and the study team did not provide device-measured activity data or specific exercise prescriptions. Residual confounding remains possible despite multivariable adjustment. The authors noted gaps that merit further study: whether increasing vigorous activity in older patients with long-standing disease yields sustained improvements in ASAS HI and SF36 scores, optimal intensity and dose of exercise prescriptions for this subgroup, and mechanisms behind the observed sex differences. These questions were not resolved by the present dataset and require prospective or interventional research to address.