Background The risk of cardiovascular (CV) disease is increased in patients with rheumatoid arthritis (RA). Systemic inflammation associated with RA may promote an increased risk of both CV risk factors and outcomes (CV morbidity and mortality). The objective of this study was to determine the incidence of CV risk factors among subjects with RA compared to those without RA, both at the time of RA diagnosis and during the disease course.
Methods We examined an already assembled retrospective population-based incidence cohort of all Rochester, MN, residents with RA (defined according to the American College of Rheumatology criteria) first diagnosed between 1955 and 1995, and an age and sex matched non-RA cohort. Each subject in the non-RA cohort was assigned an index date corresponding to the RA incidence date (baseline) of their matched RA patient. All subjects were followed up longitudinally through their complete (inpatient, outpatient) medical records beginning at age 18 years (or migration to Rochester), until death, migration, or January 1st, 2001. CV risk factors (i.e. smoking, hypertension, diabetes mellitus, dyslipidemia, body mass index) were defined using established criteria. Chi-square tests were used to compare the frequency of each CV risk factor at baseline. The incidence rate of each CV risk factor during follow-up was estimated using person-years methods and the rate ratios (RR) were obtained, with 95% confidence intervals (95% CI) estimated using an F approximation.
Results The study population included 603 RA and 603 non-RA subjects. At baseline, RA subjects were significantly more likely to have been former or current smokers compared with non-RA subjects (p<0.001). The baseline frequency of all other CV risk factors was similar in both groups. During follow-up, RA subjects were significantly more likely to have low BMI (RR: 1.79, 95% CI: 1.28, 2.54) and less likely to have dyslipidemia (RR: 0.75, 95% CI: 0.61, 0.91) compared with non-RA subjects. RA subjects also appeared less likely to be obese and diabetic than non-RA subjects during follow-up but these differences did not reach statistical significance.
Conclusions While many of the traditional CV risk factors were similar among RA compared with non-RA subjects, there were notable differences, esp. regarding the impact of dyslipidemia, smoking and BMI. The overall impact of risk factors for CV disease among persons with RA may differ in important ways when compared with the general population.