Does rheumatoid arthritis (RA) raise the risk of developing type 2 diabetes mellitus (DM)? Previous epidemiologic studies have drawn varying conclusions. Now, a large population-based cohort study bolsters the case that RA in fact is not associated with a heightened risk.
The study, published in the September Arthritis Care & Research, examined the incidence of type 2 DM in people with RA and in general non-RA, hypertension, osteoarthritis (OA) and psoriatic arthritis (PsA) cohorts. Results showed the risk of type 2 DM was lower in the RA cohort compared to other cohorts, after adjusting for potential confounding.
Seoyoung C. Kim, MD, ScD, MSCE, director of the Program in Rheumatologic, Immunologic, and Musculoskeletal PharmacoEpidemiology (PRIME) at Brigham and Women’s Hospital, is the study’s lead author. She said the results were somewhat surprising, as she and her colleagues had expected to see a greater risk of type 2 DM associated with RA.
“Patients with hypertension, OA or PsA are likely to have more shared risk factors for diabetes than the RA group,” Dr. Kim said. “Also, advances in RA treatment have helped us better control RA disease activity and minimize the use of steroids, which are a risk factor for diabetes.
“I don’t want to imply that RA is somehow protective against diabetes. But relatively speaking, based on our data, compared with the general and other disease populations, merely having RA does not increase the risk of developing type 2 DM.”
Size and Generalizability of Study Cohort a Strength
A major strength of the study, Dr. Kim noted, was its size and generalizability: It used a U.S. commercial insurance claims database of nearly 450,000 people. With such a vast data source, investigators were able to incorporate various comparison groups that were representative of the U.S. population and make a thorough assessment of baseline risks and health care utilization.
“Our study was carefully designed to account for potential differences not only in participants’ demographics, medications and other comorbidities, but also in their patterns of health care system use,” she added.
During the follow-up of a median of 1.6 years, the incidence rate of type 2 DM was 7.0 per 1,000 person-years in the RA cohort. That same rate was 7.4 in in the general non-RA cohort, 7.8 in the OA cohort, 9.9 in the PsA cohort and 12.3 in the hypertension cohort. “After adjusting for >40 baseline covariates, we found that RA was associated with a 24–35% lower risk of incident type 2 DM compared to 4 comparison groups,” according to the paper.
“These numbers provide a very good data point that you can share with a patient who asks about their chance of developing diabetes,” Dr. Kim said. “My goal is always to provide high-quality evidence that physicians can share with the patient as they make treatment decisions together, and that was part of the point of doing this study.”
Seeking Improved Outcomes in RA Patients
Dr. Kim and her colleagues conducted another study published in the April Arthritis Care & Research to determine the associations between biologic or targeted disease-modifying antirheumatic drugs (DMARDs) and the risk of incident DM in RA patients. That study found abatacept was associated with a lower such risk compared with infliximab or adalimumab.
“Certain biologic or targeted DMARDs may directly affect patients’ risk of diabetes because of their role in preserving beta cell functions.” Dr. Kim said. “Also, it is possible they have an indirect effect on the comorbidities by decreasing the systemic inflammation.”
Moving forward, Dr. Kim cautioned, failing to treat RA adequately or using long-term steroids will worsen the risks of patients developing type 2 DM and other comorbidities. Treat-to-target strategy to manage RA proactively and aggressively to control systemic inflammation, she said, will lead to better outcomes.