People who have rheumatoid arthritis (RA) are known to be more likely to develop other serious health problems, including heart disease, lung disease and some types of cancer. Now a recent study in the online journal PLOS One appears to indicate they also have a higher risk of developing type 2 diabetes.
Lead study author Piero Ruscitti, MD, of the University of L’Aquila in Italy, writes that he and his colleagues undertook the study to show that type 2 diabetes is common but often overlooked in RA patients.
For the study, the researchers followed 439 people with newly-diagnosed RA for one year, evaluating them every three months. During that time, 31 (7.1 percent) developed type 2 diabetes. The researchers then investigated the role of traditional risk factors as well as RA-specific risk factors to determine which ones predicted who might develop diabetes at then end of the 12 months.
After taking into account factors such as demographic characteristics (like age and sex), the presence of other conditions, smoking status and medications used, they found three factors that pointed to a higher risk of developing diabetes among the study group.
As might be expected, those who had impaired fasting glucose (IFG), a condition sometimes called pre-diabetes, had a more than 30-times greater chance of progressing to diabetes than someone with normal fasting glucose level. Additionally, those who had high blood pressure – a well-established risk factor for diabetes in the general population – had an almost seven-times greater risk.
But the factor that had the greatest impact was having a high RA disease activity score (DAS28) at the end of the 12 months. The DAS28, which measures how well RA is controlled, is based the amount of inflammation, joint pain and swelling a person has. A score below 2.6 indicates remission; 2.6 to 3.2 is considered low disease activity; 5.1 or above is very high and indicates uncontrolled disease.
Patients with a high DAS28 (the researchers calculated the cut-off as having a DAS28 above 3.71) were more than 33 times more likely to have diabetes at the end of the study compared with those who had lower scores.
The authors say the link between moderately active RA and diabetes makes sense; both seem to be driven by the same inflammatory proteins, especially TNF and interleukin 1 (IL-1). But the connection doesn’t stop there: Both RA and diabetes are independent risk factors for heart disease. Having just one of the conditions increases the risk; having both raises the risk even more. The authors believe that identifying and effectively treating people with this double threat can reduce the risk of heart attack and stroke.
Other findings of the study were more surprising. For example, corticosteroids are known to raise blood-sugar levels, but the researchers didn’t find that to be the case for this group of patients. Also, TNF blockers, which theoretically should help protect against diabetes, didn’t seem to do that. And obesity – normally a big risk factor for type 2 diabetes – was not found to be a risk factor.
It’s not entirely clear what to make of these findings. Jasvinder Singh, MD, a professor in the Division of Clinical Immunology and Rheumatology at the University of Alabama at Birmingham, says the study is good quality and is especially strong in adjusting for “important covariates and confounders” that might skew the results. But it has limitations, too, including “a small sample size, short follow-up duration and detection bias because the authors were carefully examining patients for the new development of type 2 diabetes.”
Furthermore, Dr. Singh, who was not involved in the study, says the results may not be the same in other settings and health systems – this study looked only at patients from a single center, and there was no control group for comparison.
One thing is for sure, though. According to the Centers for Disease Control and Prevention (CDC) in Atlanta, certain lifestyle changes like weight loss and getting more physical activity can cut the risk of type 2 diabetes by more than half in adults younger than 60 and up to 71 percent in those who are older. And, the CDC says, pre-diabetes can be completely reversed with similar lifestyle changes.
- More Than Just Joints: How Rheumatoid Arthritis Affects the Rest of Your Body
- How RA Inflammation Affects Your Heart
- Arthritis Comorbidities