Background/Purpose: As epidemiologic studies throughout the world have shown significant variations, we sought to characterize racial differences in longitudinal epidemiologic trends of adult rheumatoid arthritis (RA) in a large, racially diverse, managed care organization. The study objective was to estimate racial/ethnic differences in incidence density (ID) and prevalence rates (PR) of RA over time, while adjusting for age, and gender.

Methods: This was a retrospective population based study using active members from a large managed care health plan, during 01/01/2002 and 12/31/2010. RA patients were identified using a diagnosis code for RA in combination with the use of a disease modifying antirheumatic treatment within a year of the diagnosis code date. Subjects were required to be between the ages of 18 years and 100 years at the time of diagnosis. Non-RA adult health plan members informed the denominator for the ID and PR rates which were calculated on an annual basis. The longitudinal trend of ID and PR across 2002 to 2010, was further stratified by race/ethnic groups (Caucasian; Hispanic; African American; Asian and Other race); age (18-34; 35-44; 45-54; 55-64; and >= 65), and gender. Negative binomial regression models were used to estimate age, gender and race, adjusted rate ratios, for incidence density (aIDr) and prevalence (aPRr). The negative binomial models also included yearly dummy indicators to evaluate the statistical significance (alpha 0.05) in changes of these rates overtime.

Results: During the study period, a total of 8,108 incident cases and 58,644 prevalent cases of RA were identified. The majority of incident (76.9%) and prevalent (77.8%) cases were females. The major race/ethnic group was Caucasians, in the incident (55.8%) as well as the prevalent (64.2%) cases. Due to the predominance of females, the negative binomial models were stratified by gender. For females, the aIDr (mean (95% CI) with Caucasians as reference category) was as follows: Asian 0.7 (0.51-0.89); African Americans 1.0 (0.77-1.35); Hispanics 0.6 (0.45-0.78) and other race 0.9 (0.72-1.25). The aPRr in females (with Caucasians as reference category) was as follows: Asian 0.69 (0.56-0.83); African Americans 1.02 (0.84-1.24); Hispanics 0.45 (0.37-0.55) and other race 0.88 (0.73-1.07). Additionally, as compared to the 18-34 year age group, all other age groups had significantly higher aIDr and aPRr in both genders. Lastly, as compared to reference year 2002, the time trend for aPRr confirmed a statistically significant increase in prevalence rates in both genders.

Conclusion: We find evidence of racial differences in epidemiologic trends in RA with Asians and Hispanics having significantly lower incidence density and prevalence rates as compared to Caucasians. We also find evidence on increase in incidence and prevalence of RA with increasing age and also increase in prevalence rates over time.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/racialethnic-trends-in-incidence-and-prevalence-of-rheumatoid-arthritis-in-a-large-multi-ethnic-managed-care-population/