Although mortality among patients with rheumatoid arthritis (RA) is higher than in the general population, the relative contribution of comorbid diseases to this mortality difference is not known. This study was undertaken to evaluate the contribution of congestive heart failure (CHF) and ischemic heart disease (IHD), including myocardial infarction, to the excess mortality in patients with RA, compared with that in individuals without RA.
We assembled a population-based inception cohort of individuals living in Rochester, Minnesota, in whom RA (defined according to the criteria of the American College of Rheumatology [formerly, the American Rheumatism Association]) first developed between 1955 and 1995, and an age- and sex-matched non-RA cohort. All subjects were followed up until either death, migration from the county, or until 2001. Detailed information from the complete medical records was collected. Statistical analyses included the person-years method, cumulative incidence, and Cox regression modeling. Attributable risk analysis techniques were used to estimate the number of RA deaths that would be prevented if the incidence of CHF was the same in patients with RA and non-RA subjects.
The study population included 603 patients with RA and 603 subjects without RA. During followup, there was an excess of 123 deaths among patients with RA (345 RA deaths occurred, although only 222 such deaths were expected). The mortality rates among patients with RA and non-RA subjects were 39.0 and 29.2 per 1,000 person-years, respectively. There was a significantly higher cumulative incidence of CHF (but not IHD) in patients with RA compared with non-RA subjects (37.1% versus 27.7% at 30 years of followup, respectively; P < 0.001). The risk of death associated with either CHF or IHD was not significantly different between patients with RA and non-RA subjects. If the risk of developing CHF was the same in patients with RA and individuals without RA, the overall mortality rate difference between RA and non-RA hypothetically would be reduced from 9.8 to 8.0 excess deaths per 1,000 person-years; that is, 16 (13%) of the 123 excess deaths could be prevented.
CHF, rather than IHD, appears to be an important contributor to the excess overall mortality among patients with RA. CHF contributes to this excess mortality primarily through the increased incidence of CHF in RA, rather than increased mortality associated with CHF in patients with RA compared with non-RA subjects. Eliminating the excess risk of CHF in patients with RA could significantly improve their survival.