Epidemiology of comorbidities in early rheumatoid arthritis with emphasis on cardiovascular disease

Rheumatoid arthritis (RA) is associated with a substantially increased risk for cardiovascular (CV) morbidity and mortality. Along with their CV burden, RA patients are at increased risk for other comorbidities such as hypothyroidism and depressive symptoms. The aim of this work was to evaluate the prevalence of CV comorbidities and hypothyroidism among RA patients in comparison to those of the general population at the time of RA diagnosis. We also aimed to determine, among patients with early RA, the contribution of psychiatric and CV comorbidities as causes of long-term work disability (WD). Lastly, we assessed CV mortality rates in early RA. Between 2000 and 2007, all patients diagnosed with RA in Finland were possible to identify from a Finnish nationwide register on special reimbursements for medicine expenses. The same register provided information on the presence of comorbidities antedating RA diagnosis. From the pension registers, we retrieved data on permanent or temporary disability pensions. Causes of death were obtainable until the end of 2008. We compared the main outcomes, that is, the prevalence of comorbidities at RA diagnosis, the incidence of comorbidity-related disability pensions, and CV mortality rates to those of the age- and sex-specific Finnish population, and calculated standardized rate, incidence and mortality ratios (SRRs, SIRs, and SMRs). In a population of 7,209 RA patients, the risk of having coronary heart disease (CHD) at RA diagnosis was slightly elevated, the SRR (95% CI) being 1.10 (1.01 1.20). The SRR for levothyroxine-treated hypothyroidism at RA diagnosis was 1.51 (1.35 to 1.67). SRR was highest, almost 2.5, among women with RA aged 20 to 49, the excess prevalence of hypothyroidism decreasing steadily and fading in older age groups. From 2000 to 2008, of 7,831 RA patients, 1,095 were granted a disability pension. The 9-year cumulative incidence of WD resulting from RA was 11.9%, from a psychiatric comorbidity 1.3%, and from a CV disease 0.5%. SIR of WD resulting from CV disease was 1.75 (1.23 to 2.51) and SIR of WD resulting from psychiatric disorders was 0.99 (0.80 to 1.23). By the end of 2008, of 14,878 RA patients, 1,157 had died, 501 (43%) from CV causes. The SMR in the entire RA cohort was 0.57 (0.52 0.62). To conclude, the risks for CHD and hypothyroidism were already higher among RA patients at RA diagnosis, highlighting the importance of CV risk detection and management and of vigilance for hypothyroidism. Psychiatric and CV comorbidities were the primary causes of long-term WD much less frequently than was RA itself; the risk for WD due to CV disease, however, was higher in RA than in the general population. During the era of modern treatment regimens for RA, the risk of CV death during the early years of RA was not elevated. All these findings together stress the importance of recognizing, preventing, and targeting comorbidities in RA, already in the early years of the disease.