Mortality risk associated with rheumatoid arthritis in a prospective cohort of older women: results from the Iowa Women's Health Study

OBJECTIVE: To determine whether rheumatoid arthritis (RA) is associated with excess mortality among older women. METHODS: RA associated mortality was examined in a prospective cohort study that was started in 1986, and included 31 336 women aged 55-69 years without a history of RA at baseline. Up to 1997, 158 cases of RA were identified and validated against medical records. The relative risk (RR) and 95% confidence interval (CI) were calculated as measures of association between RA onset and subsequent mortality (overall and cause-specific) using Cox proportional hazards regression. RESULTS: Compared with non-cases, women developing RA during follow up had a significantly increased mortality risk (RR=1.52; 95% CI 1.05 to 2.20). Mortality was higher among rheumatoid factor (RF) positive cases (RR=1.90; 95% CI 1.24 to 2.92) than among RF negative cases (RR=1.00; 95% CI 0.45 to 1.99). There were trends towards increased proportions of RA related deaths from infection (RR=3.61; 95% CI 0.89-14.69) and circulatory disease (RR=1.46; 95% CI 0.76 to 2.81) but not malignancy (RR=0.97; 95% CI 0.46 to 2.04). CONCLUSIONS: RA was associated with significantly increased mortality in a cohort of older women, and the association appeared to be restricted to those with RF positive disease.