FROM ARTHRITIS & RHEUMATOLOGY
Weight loss at the time of rheumatoid arthritis diagnosis had the same impact on mortality in patients with and without RA, according to research trying to solve the so-called obesity paradox in RA, which has been related to prior observations of a protective effect of obesity on mortality in RA patients.
The finding indicates that clinicians can continue to encourage patients with rheumatoid arthritis to follow healthy weight-loss strategies, according to first author of the study, Jeffrey Sparks, MD, of Brigham and Women’s Hospital in Boston.
Dr. Sparks and his colleagues examined the impact of weight change and mortality in RA patients based on data from the Nurses’ Health Study.
“Our findings are significant because they show that weight gain did not offer a benefit for mortality among patients with RA,” Dr. Sparks said in an interview. “Prior to the study, there was the suggestion that weight gain or continued obesity might offer a protection from death for patients with RA,” he said.
“Our study is the first to focus on weight change around RA diagnosis and risk of death, rather than weight change in patients who had RA for many years,” Dr. Sparks noted.
By examining changes in weight near the time of RA diagnosis, Dr. Sparks and his colleagues said that they hoped to extract information about RA-specific processes rather than the underlying pathologies that might cause weight changes near the end of life.
In the study published in Arthritis & Rheumatology , the researchers compared women diagnosed with RA during follow-up to women without RA during the same index time period of 1976-2016. The study population included 121,701 women. Of these, 902 developed incident RA and were matched with 7,884 non-RA controls.
During an average of 18 years of follow-up, 41% of the RA cohort and 29% of the controls died. The risk of death was approximately twice as high (hazard ratio, 2.78; 95% confidence interval, 1.58-4.89) among those with weight loss greater than 30 pounds at the time of RA diagnosis, compared with those whose weight remained stable. However, the risk for mortality was similarly increased (HR, 2.16; 95% CI, 1.61-2.88) among the controls with weight loss greater than 30 pounds, compared with those with stable weight. No association with mortality was noted in either group among women who gained more than 30 pounds at the time of RA diagnosis.
Dr. Sparks said he was somewhat surprised by the findings.
“We expected severe, pathologic weight loss to be associated with increased risk of death among patients with RA and comparators. It was somewhat surprising that the risks in both groups were similar,” he said. “Conversely, prior studies suggested that weight gain might have been associated with increased risk of death. However, we found no association of weight gain with risk of death,” he noted.
In addition, “Our findings argue that there is not an RA-specific mortality risk based on either weight loss or gain,” he said. “While we found that weight loss was associated with increased mortality, this was most pronounced in the severe weight loss group, so was likely due to unintentional weight loss.”
Joshua F. Baker, MD, of the University of Pennsylvania, Philadelphia, and his colleagues identified an association between weight change and risk of death in RA patients in a study first published online in Arthritis & Rheumatology in 2015 ( Arthritis Rheumatol. 2015 Jul;67[7]:1711-17 ). That study addressed the so-called obesity paradox in RA, and Dr. Baker and his colleagues noted that weight loss associated with the development of chronic illness is a significant confounder that may explain the observed protective effect of obesity on mortality.
Dr. Sparks and his coauthors “felt it was important to determine if the associations between weight loss and mortality that have been observed in RA were similar to associations seen in the general population,” Dr. Baker said in an interview. Their findings make a lot of sense, and the authors were able to confirm that weight loss (and likely unintentional weight loss) “is a poor prognostic sign, regardless of its cause,” he said. “This study confirms prior studies that weight loss is a poor prognostic sign in RA, as it is in other conditions and settings,” he added. “Since weight loss is more commonly observed in RA, rheumatologists may see this occur more frequently. This also means that the bias that we see in epidemiologic studies when looking at weight and mortality is likely to be worse in studies of RA, though this study didn’t look at this question,” he said.
“It is not clear how best to monitor changes in weight, when exactly to become concerned, and what to do when changes are observed,” Dr. Baker noted. “RA patients may lose weight for a number of reasons, not all related to their arthritis, and it is unlikely that there is a ‘one size fits all’ approach,” he said.
The study was limited in part by the women-only study population, so the results might not be generalizable to men, Dr. Sparks said. “The reason for weight change was unavailable,” he added. Directions for further research include investigation of how factors such as physical activity, diet, and weight loss may affect the risk of death among individuals with and without RA, he said.
Dr. Sparks had no financial conflicts to disclose. The study was supported in part by the National Institutes of Health and the Rheumatology Research Foundation’s Disease-Targeted Innovative Award and Scientist Development Awards.
SOURCE: Sparks J et al. Arthritis Rheumatol. 2017 Nov 30. doi: 10.1002/art.40346 .
