Rheumatoid arthritis patients had a 40% increased risk of atrial fibrillation and a 30% increased risk of stroke compared to the general population, based on data from a national cohort study in Denmark.
Previous studies have shown an association between rheumatoid arthritis (RA) and increased risk of myocardial infarction, but data on the risk of stroke have been inconsistent, said Dr. Jesper Lindhardsen, a research fellow in the department of cardiology at Gentofte Hospital in Hellerup, Denmark.
The findings were published online March 8 in the British Medical Journal (BMJ 2012 March 8 [doi: 10.1136/bmj.e1257]).
Dr. Lindhardsen and colleagues reviewed data from a national registry that included all Danish individuals older than 15 years of age as of Jan. 1, 1997. The study cohort included 4.3 million individuals. Of these, 18,247 had RA. During a follow-up period of up to 13 years, a total of 156,484 individuals, including 774 RA patients, were diagnosed with atrial fibrillation, and 165,343 individuals, including 718 RA patients, had a stroke.
The incidence of atrial fibrillation (a modifiable risk factor for stroke) was 8.2 events per 1,000 person-years in RA patients vs. 6 events per 1,000 person years in the general population. Women were at slightly increased risk, compared with men, and the risk was significantly higher in the youngest age groups. "The absolute risk attributable to rheumatoid arthritis ranged from 25% in the oldest to 70% in the youngest age group," the researchers noted.
The incidence of stroke was 7.6 per 1,000 person-years among RA patients vs. 5.7 per 1,000 person-years in the general population. As with atrial fibrillation, the relative risk for stroke in RA patients was highest in the younger age groups.
"Nonetheless, the absolute differences in rates of atrial fibrillation and stroke between people with and without rheumatoid arthritis were highest in the oldest patients," the researchers said.
The study is the first known to examine the incidence of atrial fibrillation in a large population of RA patients. The results were limited by the use of a national registry, which missed patients not seen in clinics or treated with antirheumatic drugs during the study period.
However, the findings correspond to one new case of atrial fibrillation per 12 RA patients followed for 10 years after their diagnoses, the researchers said. Therefore, the researchers recommended that clinical care of RA patients include screening for atrial fibrillation.
"This study also underlines the importance of rigorous control of inflammation with disease modifying antirheumatic drugs, not only for the management of joint symptoms but also to reduce the need for drugs with potential adverse cardiovascular effects and, ultimately, to diminish the inflammation driven atherothrombotic process," they emphasized.
The findings are a continuation of data presented by Dr. Lindhardsen at the European Society of Cardiology meeting in 2010 in Stockholm.
Dr. Lindhardsen said he had no financial conflicts to disclose.