Epidemiology and sociodemographics of systemic lupus erythematosus and lupus nephritis among US adults with Medicaid coverage, 2000-2004.

TLDR: There was sociodemographic variation in SLE and LN prevalence and incidence in this nationwide Medicaid population, and the areas with lowest SES had the highest prevalence; areas with the fewest ACR rheumatologists had the lowest prevalence.

Abstract: Systemic lupus erythematosus (SLE) is a complex autoimmune disease with substantial variation by sex, race, ethnicity and socioeconomic status (1–4). Past estimates of SLE prevalence in the adult U.S. population range from 24 to 150 per 100,000 (5, 6) and incidence from 2.2 to 5.6 per 100,000 (7, 8) (Table 1). Despite the wide variation in these estimates, rates are consistently higher in women compared to men and in African Americans compared to Caucasians. Prior studies also suggest increased prevalence among Asians, Hispanics and Native Americans (2, 9–11). To date, however, there are no U.S. nationwide administrative database examinations of the sociodemographics of adult SLE prevalence or incidence. A number of studies suggest that lupus nephritis (LN), one of the most severe manifestations of SLE, is both more common and more severe in racial and ethnic minorities, and progression to end-stage renal disease is higher in minority, uninsured, and low socioeconomic status (SES) groups (3, 11–18). Currently, no studies are available that investigate the prevalence or incidence of LN in a large, low-income U.S. population. Table 1 Previous Estimates of the Prevalence and Incidence of Systemic Lupus Erythematosus (SLE) in the U.S. per 100,000 Adults In this study we used nationwide Medicaid claims data to investigate sociodemographic differences in the incidence and prevalence of SLE and LN among U.S. adults. Medicaid is a U.S. federal-state jointly run insurance program that provides health and long-term care coverage to eligible low-income individuals (19). Within this population, we investigated whether county-level SES and the number of rheumatologists per state (approximated using American College of Rheumatology (ACR) members), were related to differences in incidence and prevalence of SLE and LN, and the degree to which these variables could explain variation by race and ethnicity. Our goal was to provide a better understanding of the burden of SLE and LN among low-income, high-risk U.S. adults, which will encourage the necessary allocation of resources for early detection and essential treatment. We hypothesized that there would be significant variation in incidence and prevalence of SLE and LN by sociodemographic group, but that SES and the number of rheumatologists would modify these differences.