Researchers call it the obesity paradox: the phenomenon, observed in studies of patients with rheumatoid arthritis (RA) and other chronic conditions, where patients who are obese have a lower risk of death than those who weigh less. But most of these studies focused on patients who have RA for many years, and involved relatively little follow-up prior to death. Researchers from Brigham and Women's Hospital evaluated the effect of RA diagnosis on weight change and how this subsequently affects mortality risk. They did this by comparing women from the Nurses' Health Study who had been diagnosed with RA to a similar group of women who had not been diagnosed with RA. Their results suggest that the findings from previous studies regarding lower weight being associated with higher mortality may not be directly related to RA and instead reflect a more generalized phenomenon. Their study is published this week in Arthritis & Rheumatology.

"Our findings are important because they show that weight gain does not offer a mortality benefit for patients with RA," said Jeffrey Sparks. "Our observations indicate that clinicians can encourage healthy weight loss strategies for RA patients."

Prior studies testing the relationship between RA and weight loss have typically been performed by including only patients with RA, making it unclear whether the patterns reported were specific to RA or related to general population that was frail and of advanced age. In the current study, the research team narrowed in on the early RA period around the time when women were diagnosed with RA, two to four years after diagnosis or a similar period for women who were comparators. In both RA and the comparator groups, those who had severe weight loss (30 pounds or more) had the highest risk of death decades later. This increased mortality risk for severe weight loss was most likely related to unintentional weight loss, rather than healthy weight loss. Weight gain in this early RA or index period had no effect on mortality risk for either the RA or comparator groups.

"There has been a question among clinicians of whether obesity might offer a mortality benefit for patients with RA, but our data suggest that weight gain was not protective. Instead, we wonder whether people who gain or maintain weight have better observed mortality rates because they aren't sick, unlike those who unintentionally lose weight," said Sparks.

The research team accounted for certain factors -- such as physical activity and diet -- that might contribute to weight loss, but in the future, would like to understand the mechanisms for how weight change may influence risk of death.