Prognostic importance of low body mass index in relation to cardiovascular mortality in rheumatoid arthritis

Objective. Various etiologic mechanisms have been implicated in the observed increase in cardiovascular mortality in rheumatoid arthritis (RA). Body mass index (BMI) is associated with cardiovascular mortality in the general population. This study compared the effect of BMI on cardiovascular mortality in a population-based cohort of subjects with RA with that in a cohort of individuals without RA from the same population. Methods. The RA cohort comprised all members of an incidence cohort of Rochester, Minnesota residents ages :18 years who were first diagnosed with RA (by the American College of Rheumatology 1987 criteria) from 1955 through 1994. An age- and sex-matched comparison cohort of subjects without RA was assembled. Both cohorts were followed up longitudinally through their complete (inpatient, outpatient) medical records beginning at age 18 years and continuing until death, migration, or January 1, 2001, and the details of weight and height changes during this period were recorded. High BMI was defined as a BMI >30 kg/m(2) and low BMI as <20 kg/m(2). Cox regression models were used to estimate the effect of BMI on cardiovascular mortality after accounting for traditional cardiac risk factors and malignancies. Results. RA subjects with low BMI at incidence had a significantly higher risk of cardiovascular death (hazard ratio [HR] 3.34, 95% confidence interval [95% CI] 2.23-4.99) compared with non-RA subjects with normal BMI, after adjusting for age, sex, personal cardiac history, smoking status, and presence of diabetes, hypertension, and malignancies. RA subjects with normal BMI at incidence who experienced low BMI during followup also had a higher risk of cardiovascular death (HR 2.09, 95% CI 1.50-2.92) when compared with non-RA subjects who maintained normal BMI throughout followup. Conclusion. Among patients with RA, low BMI is associated with a significantly increased risk of cardiovascular death.