RHEUMATOID-ARTHRITIS AND MORTALITY - A LONGITUDINAL-STUDY IN PIMA-INDIANS

Objective. To determine the effect of rheumatoid arthritis (RA) on mortality rates. Methods. Longitudinal analyses of data from a cohort of Pima Indians from the Gila River Indian Community in Arizona, who were followed up during the period February 1965 through December 1989. Results. Among 2,979 study subjects aged greater-than-or-equal-to 25 years, there were 858 deaths, 79 of which occurred in subjects with RA (36 men, 43 women). Age- and sex-adjusted mortality rates were slightly higher in subjects with RA than in those without (mortality rate ratio 1.28, 95% confidence interval [95% CI] 1.01-1.62). Among those with RA, mortality rates were higher in older subjects (mortality rate ratio 1.51 per 10-year increase in age, 95% CI 1.22-1.88), in male subjects (mortality rate ratio 2.23, 95% CI 1.44-3.45, adjusted for age), and in subjects with proteinuria (mortality rate ratio 1.88, 95% CI 1.02-3.46, adjusted for age and sex). Mortality rate ratios for these risk factors were similar in subjects without RA. In addition, among subjects with RA, rheumatoid factor (RF) positivity was predictive of death (mortality rate ratio 1.94, 95% CI 1.10-3.43), and the excess mortality was found primarily among subjects who were seropositive. The death rate from cardiovascular disease (mortality rate ratio 1.77, 95% CI 1.10-2.84) and from liver cirrhosis or other alcohol-related disease (mortality rate ratio 2.52, 95% CI 1.06-6.01) was increased in persons with RA. Conclusion. The results of this population-based study suggest that although the risk of mortality in subjects with RA is significantly higher than in those without RA, the risk ratio is in the lower range of that described previously in studies of clinic-based cohorts. RF positivity as a predictor of early death among subjects with RA indicates that the immunologic processes in seropositive RA may contribute to the events that eventually lead to early death.