Highly physically active women at low risk of rheumatoid arthritis
High physical activity levels reduce the risk of developing rheumatoid arthritis (RA) in women, a study has found.
The study involved 113,366 participants from the Nurses' Health Study II, among whom 506 developed RA (67.0 percent had seropositive RA) over 2,428,573 person‐years of follow‐up. Every participant completed biennial questionnaires to determine physical activity exposures and covariates.
Researchers evaluated the long‐term cumulative average number of hours spent in recreational physical activity 2–8 years prior to the RA diagnosis. This time span was chosen to reduce the potential for reverse causation bias, given that early RA affects physical activity prior to diagnosis.
Multivariable Cox regression analysis revealed that increasing cumulative average total hours of recreational physical activity had a protective association with the risk of RA. Relative to women engaging in <1 hour of physical activity per week, those who were more physically active had up to about a 30-percent lower risk of developing RA (2 to <4 hours/week: hazard ratio [HR], 0.92, 95 percent CI, 0.72–1.17; 4 to <7 hours/week: HR, 0.84, 0.63–1.12; ≥7 hours/week: HR, 0.67, 0.47–0.98; p-trend=0.02).
Body mass index mediated some of the effect of physical activity on all RA (14.0 percent; p=0.002) and on seropositive RA (20.0 percent; p=0.001), suggesting that both physical activity and weight-loss interventions could delay or even prevent the onset of seropositive RA, according to the researchers.
The present data contribute to the increasing evidence that metabolic factors play an important role in RA pathogenesis, they added.