A study by Hospital for Special Surgery (HSS) researchers finds that body mass index (BMI) plays a role in rheumatoid arthritis (RA) patients' ability to achieve a sustained remission. Looking at patients who had received an RA diagnosis within the past 12 months, investigators found that those who were significantly underweight or overweight/obese were the least likely to remain in remission.
The study, titled, "Very Low or High Body Mass Index Negatively Affects Patients' Ability to Achieve Sustained Remission in Early RA in a Multicenter Canadian Cohort," was presented at the American College of Rheumatology annual meeting in Boston.
Researchers set out to determine if early RA patients with a very low BMI (<18.5) or high BMI (≥ 25) were able to achieve a sustained remission. Patients were grouped by BMI categories and symptoms were measured prospectively over three years in patients participating in the CATCH (Canadian Early Arthritis Cohort) study using the Disease Activity Score for RA (DAS28).
The DAS28, which measures the number of swollen and tender joints, as well as inflammation markers in the blood and the patients' own assessment of their disease, is used to determine the severity of RA and can indicate if a patient is in remission. In the study, sustained remission was defined as having low disease activity at two consecutive doctor visits three to six months apart.
A total of 944 patients were categorized into six groups based on World Health Organization BMI classifications. Researchers analyzed data for eligible patients with a measured BMI and at least two consecutively measured DAS28 scores over three years.
Only two percent of patients were underweight and 65 percent were either overweight or obese. Patients with a higher BMI were older, more often female and had worse function. Those with a very low or high BMI had more inflammation, and those with a low or normal BMI were more often smokers.
"What's striking is that if you look at the BMI classifications, all the patients in the underweight or overweight categories were much less likely to achieve sustained remission compared to those with a normal BMI," said Susan Goodman, M.D., a rheumatologist at HSS. "Patients who were severely obese had an even lower chance of achieving sustained remission. Individuals in the highest BMI categories also had more inflammation and more pain."
When looking at other contributing factors, the researchers found that early use of methotrexate, nonsmoker status and responding to treatment within the first six months increased the chances of achieving a sustained remission, independent of BMI.
"It is important to identify possible factors we can modify to help patients with this disease," said Vivian Bykerk, M.D., principal investigator and director of the Inflammatory Arthritis Center at HSS. "We also saw that those who smoked were less able to achieve sustained remission."
"Our findings represent the first study to present evidence that BMI should be considered among the modifiable risk factors for poor RA outcomes," said Dr. Goodman. "There are many things patients can do to manage the disease. Along with timely diagnosis and treatment, weight control and other good practices can result in better outcomes."
Dr. Bykerk and her team at Hospital for Special Surgery have initiated an American Early Arthritis Cohort (CATCH-U.S.) study and have begun to enroll patients. The study will be expanded to include a multicenter cohort at eight additional U.S. sites to expand this collaboration. The centers will enroll patients with early inflammatory arthritis thought to be RA to compile information on outcomes and determine best practices.