The results are in…and they might seem unusual. Researchers in Sweden have found that a high body mass index (BMI) could reduce the risk of rheumatoid arthritis (RA) in men. The study, published in Rheumatology, did not find this to be true for women.
High BMI Reduces Risk of RA…in Men
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The researchers analyzed data from 383 patients (taken from two population based health surveys with a total of 50, 705 participants). The results were based on the Malmö Diet Cancer Study (MCDS) and Malmö Preventative Medicine Program (MPMP) data sets.
Carl Turesson, M.D., Ph.D. is a rheumatologist at Malmö University Hospital, and was lead author of the paper. He commented in the September 8, 2015 news release: “to our knowledge, this is the first nested case-control study to investigate this issue in men.” He went on to comment on the effect for overweight and obese participants: “the effect of obesity on the risk of RA did not appear to be substantially different from that of overweight. However, a differential effect of very high BMI cannot be ruled out.”
After the results had been adjusted for smoking, as that has been found to be negatively associated with obesity in men, men with a BMI over 25kg/m2 were estimated to be 63% less likely to develop RA in the MDCS, and 40% less likely in the MPMP. When looking into why a high BMI would reduce the risk of men developing RA in the future, the scientists suggested that a high BMI more often reflects increased abdominal obesity or visceral fat in men compared with women, which could be protective against the development of RA. They have previously described a connection between high BMI and hormones, where metabolic pathways related to the adipose tissue and hormone-related factors could have a protective effect against RA.
Dr. Turesson told OTW, “We were surprised to learn that the negative association between overweight/obesity and future RA was as strong in the subset of cases who developed RA > 12 years later and their controls as in the rest of the sample. This suggests long term effects of metabolic pathways on the risk of RA.”
“This is an example of research where rheumatologists explore the mechanisms of disease development. Through these efforts, we hope to move beyond management of consequences of RA towards cure, and even prevention. I hope this perspective may be of interest to orthopedic surgeons.”
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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