SAN DIEGO – Women who regularly drink one or more sugar-sweetened soft drinks per day are at heightened risk of developing seropositive rheumatoid arthritis, according to a massive analysis of combined data from the prospective-cohort Nurses’ Health Study and Nurses’ Health Study II.
During 1.9 million person-years of prospective follow-up in the Nurses' Health Study (NHS) and 1.5 million person-years in NHS II, there were 563 confirmed cases of new-onset seropositive rheumatoid arthritis and 320 cases of seronegative rheumatoid arthritis. The two studies collectively enrolled 238,131 U.S. female registered nurses who periodically filled out validated food frequency questionnaires.
In a multivariate analysis adjusted for numerous potential confounding variables, women who reported drinking an average of one or more non-diet sodas per day had a 71% greater risk of developing seropositive rheumatoid arthritis during follow-up than did those who drank none or less than one per month (P = .005), Yang Hu reported at the annual meeting of the American College of Rheumatology.
It’s noteworthy that the increased risk was present at a cut point of one daily serving, a level of consumption many Americans wouldn’t view as excessive.
The mechanism for the observed association between frequent soft drink consumption and seropositive rheumatoid arthritis remains unclear. The investigators decided to look at sugar-containing soda consumption because it has been shown to be associated with overweight and obesity, type 2 diabetes, and cardiovascular disease. And since obesity has previously been shown to be associated with increased risk of rheumatoid arthritis, the thinking was that obesity might mediate the link between soda consumption and rheumatoid arthritis. Daily soda consumption, however, was independently associated with a 71% increase in risk even after controlling for body mass index in the multivariate analysis, noted Mr. Hu of Brigham and Women’s Hospital, Boston.
Other potential confounders that were adjusted for in the analysis included age, smoking, alcohol consumption, physical activity, reproductive factors, multivitamin use, income level, and diet quality.
The NHS and NHS II studies are funded by the National Institutes of Health. Mr. Hu reported having no financial conflicts of interest, but one of his associates disclosed relationships with several pharmaceutical companies.
*Correction, 11/15/2013: An earlier version of the article misstated the number of nurses involved in the analysis.