The authors note that although they designed the study to minimize the potential for reverse causation bias, it’s possible the association between exercise and RA may be explained by symptoms of early RA. But if that were the case, these symptoms would had to have occurred two to eight years prior to clinical diagnosis.
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Nevertheless, because one of the first symptoms of RA is a limitation in physical activity, the investigators performed a secondary analysis in which they lagged the assessment of physical activity and RA risk window by an additional questionnaire cycle. This secondary analysis expanded the window between physical activity assessment and the RA risk window to at least 4–10 years. Although the analysis included fewer RA cases, the results matched those seen in the primary analysis, suggesting this documented decrease in activity would have to be a very early symptom if it were a symptom at all.
A Key Prevention Tool
Like previous studies, this research identified a statistically significant effect among women with brisk and very brisk walking paces such that longer cumulative average walking hours weekly appeared to reduce the risk of RA. Because walking seemed to be the main contributor to the composite variable of recreational activity, the researchers investigated it more closely. They found brisk and very brisk walking—but not an easy or average walking pace—seemed to be the activity driving the association between recreational activity and RA.
Senior author Jeffrey A. Sparks, MD, MMSc, an assistant professor of medicine at Brigham and Women’s Hospital and Harvard Medical School, Boston, explained that although he expected to see this sort of association in the year before RA diagnosis, he was surprised to see a clear and consistent association even many years before RA diagnosis. Moreover, he notes that walking is an activity that most people can do.
“We really saw a trend,” he says. “Increasing your physical activity seems to have a protective effect for RA risk. This is good news. There is a way to reduce your risk.”
Lara C. Pullen, PhD, is a medical writer based in the Chicago area.
References
- Krok-Schoen JL, Brasky TM, Hunt RP, at al. Dietary long-chain n-3 fatty acid intake and arthritis risk in the Women’s Health Initiative. J Acad Nutr Diet. 2018 Nov;118(11):2057–2069.
- X Liu, SK Tedeschi, B Lu, et al. Long-term physical activity and subsequent risk for rheumatoid arthritis among women: a prospective cohort study. Arthritis Rheumatol. 2019 Sep;71(9):1460–1471.