Physical activity reduces the risk of osteoporosis in patients with arthritis: A dual-cohort prospective study and mechanistic exploration.

BACKGROUND

Osteoporosis is a major complication in patients with arthritis, yet the long-term protective effect of physical activity (PA) and its underlying mechanisms are not fully understood.

METHODS

This study utilized two large aging cohorts, the U.S. Health and Retirement Study (HRS) and the English Longitudinal Study of Ageing (ELSA). All exposures and outcomes, including PA and physician-diagnosed arthritis and osteoporosis, were based on self-reported data. Cross-sectional analyses assessed the association between PA and arthritis-osteoporosis comorbidity. Longitudinal Cox models examined the effect of baseline PA on new-onset osteoporosis in patients with arthritis. Subgroup, E-value, and mediation analyses were performed to explore effect heterogeneity, robustness, and the mediating role of depression. An exploratory reverse analysis assessed the association of PA with new-onset arthritis in osteoporosis patients.

RESULTS

Among 20,175 HRS and 10,525 ELSA participants in the cross-sectional analysis, and 8032 HRS and 2984 patients with arthritis in the prospective analysis, PA was associated with lower comorbidity prevalence (HRS: OR = 0.78; ELSA: OR = 0.69). In longitudinal analyses, active PA was independently associated with reduced osteoporosis risk (HRS: HR = 0.86; ELSA: HR = 0.70) in patients with arthritis. The effect was more pronounced in younger patients and those with heart disease or depression. In HRS, depression significantly mediated 36.55% of the protective effect, whereas this mediation pathway was non-significant in ELSA. No significant association was found between PA and new-onset arthritis in osteoporosis patients.

CONCLUSION

Regular physical activity was associated with a lower risk of osteoporosis in patients with arthritis; the association may be partly explained by improvements in depressive symptoms. Promoting PA should be integral to clinical management.