COPENHAGEN, DENMARK. It is well established that rheumatoid arthritis (RA) is associated with an increased risk of heart attack (myocardial infarction) and heart failure. Now Danish researchers report that RA is also associated with an increased risk of atrial fibrillation (AF) and stroke (ischemic and hemorrhagic). Their study included the entire Danish populations over the age of 15 years at January 1, 1997. After eliminating about 100,000 persons with previous AF, stroke or RA, the study cohort was 4,182,335 people. The members of the cohort were followed for 13 years or until death, emigration or the diagnosis of RA, AF or stroke.

During follow-up, 18,247 participants were diagnosed with RA. The diagnosis was made at an average age of 59 years and most (70%) of RA patients were women. Also during follow-up, a total of 165,343 cohort members, including 718 with RA, experienced a stroke (ischemic or hemorrhagic) and 156,484 including 774 with RA were diagnosed with AF. The incidence rate of AF was found to be 0.82%/year in RA patients and 0.6%/year in the general population, corresponding to an age- and sex-adjusted incidence rate ratio of 1.41. In other words, patients with RA had a 41% (relative) increased risk of being diagnosed with AF than did a member of the general population. The incidence of stroke was 0.76%/year in RA patients and 0.57%/year in the general population, corresponding to an age- and sex-adjusted incidence rate ratio of 1.32 or a 32% (relative) increased risk of suffering a stroke when compared to the general population.

The relative risk of RA patients being diagnosed with AF or stroke was 3-fold higher among younger patients (age below 50 years) than among older ones. However, the actual incidence of AF in people below the age of 50 years was very low (below 0.05%/year). The researchers conclude that RA is associated with an increased risk of AF and stroke and recommend that RA patients be routinely checked for AF.
Lindhardsen, J, et al. Risk of atrial fibrillation and stroke in rheumatoid arthritis. British Medical Journal, March 8, 2012 [Epub ahead of print]

Editor's comment: It is not surprising that RA patients are more likely to be diagnosed with AF than are members of the general population. After all, the two conditions share several characteristics including the likely presence of systemic inflammation, heart disease, heart failure, and atherosclerosis. The question is, "Is a 40% (relative) increase in risk of being diagnosed with AF really relevant?" Essentially, the results of the Danish study mean that, in a group of RA patients, 8 out of 1000 will develop AF during a 1-year follow-up as compared to 6 members of the general population.