Among women, higher levels of physical activity may be associated with a reduced risk of developing rheumatoid arthritis (RA), according to results published in Arthritis & Rheumatology.
The study included participants from the Nurses’ Health Study II (1989-2015). The researchers collected information on physical activity exposures and covariates, using biennial questionnaires. For participants who self-reported RA on the questionnaire and screened positive on a supplemental survey, medical records were reviewed by 2 independent rheumatologists to confirm the diagnosis.
The primary outcome was whether long-term cumulative average recreational physical activity 2 to 8 years before RA diagnosis could reduce the potential for reverse causation bias. The researchers calculated Cox regression estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for RA serologic phenotypes (all, seropositive, seronegative) by physical activity category. They adjusted for body mass index (BMI) at age 18 years, as well as time-varying potential confounders.
Of 113,366 women with 2,428,573 person-years of follow-up, the researchers identified 506 incident RA cases. Of these, 67.0% were seropositive.
After adjusting for confounders, the results indicated that an increased cumulative average of recreational physical activity was associated with a decreased risk for RA. For women who performed physical activity for an average of <1 hour/week, the HR was 1.00; for 1 to <2 hours/week, the HR was 1.00 (95% CI, 0.78-1.29); for 2 to <4 hours/week, the HR was 0.92 (95% CI, 0.72-1.17); for 4 to <7 hours/week, the HR was 0.84 (95% CI, 0.63-1.12); and for ≥7 hours/week, the HR was 0.67 (95% CI, 0.47-0.98; P trend=.02).
“We found that some of the risk of physical activity on seropositive RA was mediated by changes in BMI, suggesting that both physical activity and weight loss interventions could delay or even prevent seropositive RA onset,” the researchers wrote.