Published in May in Arthritis & Rheumatology, the report, “Weight loss, the obesity paradox and the risk of death in rheumatoid arthritis,” found that, although lower body mass index (BMI) is associated with improved outcomes in the general population, it has been associated with premature death in patients with rheumatoid arthritis (RA). As the first study to comprehensively look at the role of weight loss over time in predicting death in patients with RA, it helps explain this “obesity paradox,” in which weight loss—not low BMI, per se—is a strong predictor of mortality.
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“What our study tried to do is take [the research] a step further and … figure out why that is and get at the idea that perhaps this is all due to confounding by disease-related weight loss,” says lead author Joshua Baker, MD, MSCE, a rheumatologist at the University Hospital of the University of Pennsylvania in Philadelphia. “This confounding … really causes you to underestimate the risks of obesity.”
The report, which used data from the Department of Veterans Affairs, found that a loss in BMI greater than or equal to 1 kg/m2 was associated with a greater risk of death after adjusting for demographics, comorbidities, BMI, smoking and RA therapies (HR 1.99 [CI 1.53, 2.59], p<0.001). Weight loss at an annualized rate of greater than or equal to 3 kg/m2 was associated with the greatest risk of death (HR 2.49 [1.73, 3.57], p<0.001).1
Dr. Baker says the focus of the current paper and future research is on unintentional weight loss, because those patients with RA who shed pounds via exercise or controlled diets are not likely to be at risk.
“It may also be helpful to think about how body composition changes,” Dr. Baker adds. “So, not just weight loss, but also how your lean mass and your fat mass and your distribution of fat change over time. If we can identify why those things happen and how those things happen in the setting of RA … then we could use those things as a better way of predicting risk.
“Maybe asking people about weight histories in epidemiologic studies is something we should be doing to try and get around this confounding by weight loss and better estimate the risks of obesity,” Dr. Baker says.
Richard Quinn is a freelance writer in New Jersey.
Reference
- Baker JF, Billig E, Michaud K, et al. Weight loss, the obesity paradox, and the risk of death in rheumatoid arthritis. Arthritis Rheumatol. 24 May 2015. DOI: 10.1002/art.39136