Being underweight or experiencing rapid weight loss are both independently associated with an increased risk of cause-specific mortality in individuals with rheumatoid arthritis, according to new research.

In a cohort of 1,600 U.S. veterans with rheumatoid arthritis who were followed for a median of 3.2 years, researchers found that being overweight (BMI 25-30 kg/m2) was associated with a 41% lower risk of cardiovascular mortality. Cumulative weight loss of greater than 10% and weight loss greater than 3 kg/m2 per year were both significantly associated with a twofold higher risk of cardiovascular mortality.

Similarly, more rapid weight loss of more than 3 kg/m2 per year was also associated with a greater than twofold increase in the risk of cancer mortality, while less rapid weight loss did not show a significant impact (Arthritis Care Res. 2017 Apr 20. doi: 10.1002/acr.23258 ).

Individuals who were underweight (BMI less than 20 kg/m2) had nearly a threefold greater risk of respiratory mortality, compared with individuals with a normal BMI. Researchers saw a dose-dependent association between respiratory mortality and percent of weight loss: 5%-10% weight loss was associated with an 86% higher risk of respiratory mortality, and greater than 10% weight loss showed a more than twofold greater risk.

This appears to be the first study to examine the impact of both BMI and weight loss on cause-specific mortality in rheumatoid arthritis, according to Bryant R. England, MD, of the VA Nebraska-Western Iowa Healthcare System of Nebraska, Omaha, and his coauthors.

“In this study of cause-specific mortality, we again demonstrate that underweight BMI and weight loss both drive mortality risk, but, importantly, this risk may differ across causes,” they wrote. “In cardiovascular and cancer mortality, we identified rapid and cumulative weight loss as the weight parameters most predictive of death, while in respiratory mortality underweight BMI was the weight parameter most predictive.”

Weight loss most likely reflects a systematic process, such as inflammation, that is a well-known risk factor for cardiovascular disease and mortality in people with rheumatoid arthritis, the authors suggested. Weight loss may also reflect comorbidities, chronic illness, disease phenotype, aging, smoking, and other factors, they said.

“Overall, these data illustrate the importance of considering the dynamic nature of body composition when assessing mortality risk in RA,” they said.

The authors noted that, while the study population was predominantly composed of older men, their findings were largely in agreement with those from studies with a higher proportion of women.

The researchers received grant support from the Department of Veterans’ Affairs and the National Institutes of Health. They reported having no conflicts of interest.