Low prevalence of rheumatoid arthritis among patients with pre-existing type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a non-autoimmune disease characterized by chronic hyperglycemia and increased non-enzymatic glycation of amino groups. Glycation occurs through a series of events eventually leading to the formation of irreversible "advanced glycation end-products" (AGEs). AGEs may affect the function of long-lived proteins, including cytokines, immunoglobulins and their receptors, resulting in a "less active" immune system. We aimed to test the hypothesis that a common inflammatory chronic disease, such as rheumatoid arthritis (RA), in which the earliest event is an inflammatory response to unknown stimulus, has a lower prevalence in these patients than in normoglycemic, non-diabetic subjects.

In this study, we compared the prevalence of RA in a prospectively followed outpatient cohort of patients with T2DM patients (n=1,630) with a control, matched, non-diabetic population (n=1,630).

Among non-diabetic controls, 13 patients (prevalence 0.80%) with RA were identified. An almost 3-fold lower prevalence of RA (0.25%) was found in consecutive patients with T2DM (P=0.029). Most of the RA cases among participants with T2DM were diagnosed early after diabetes onset. The onset of RA in patients with T2DM occurred at significantly older age (64±15 years) as compared to the non-diabetes group (48±18 years; P=0.004).

The prevalence of RA is lower and occurs in an older age in patients with pre-existing T2DM in comparison with people without T2DM.