Liu X, et al. - Investigators studied long-term physical activity in relation to the consequent risk for rheumatoid arthritis (RA) among females in the Nurses' Health Study II (1989-2015). They noticed a correlation between increasing cumulative average total hours of recreational physical activity and reduced RA risk. They recorded 506 incident RA cases during ~2.4 million person-years of follow-up. They found 14.0% to be the proportion of the effect between physical activity and RA mediated by updated body mass index for all RA vs 20.0% for seropositive RA. They also reported an association of higher levels of physical activity with reduced RA risk.