Background Cardiovascular disease (CVD) is the leading cause of death among SLE patients, with significantly elevated risks of myocardial infarction (MI) and stroke among SLE patients compared to age-matched controls. The objective of our study was to examine the rates of non-fatal MI, stroke, and the combined endpoint of non-fatal MI or stroke, overall and by race/ethnicity, among SLE patients enrolled in Medicaid.
Materials and methods Within Medicaid Analytic eXtract (MAX), containing billing claims from 2000–10 for Medicaid patients from the 29 most populated US states, we identified patients aged 18–65 with prevalent SLE (≥ 3 ICD-9 codes 710.0, ≥30 days apart) with >12 months of continuous enrollment prior to 3rd code (index date). Baseline data from 12 months prior to index date included age, sex, race/ethnicity, zip code, year, SLE-related and other comorbidities, including CVD risk factors (based on ICD-9 and DRG codes). Those missing race/ethnicity were excluded. Subjects were followed from index date to first MI or stroke event, death, Medicaid disenrollment, or end of follow-up. MI, stroke, and combined outcome per 1000 person-years with 95% CIs were calculated overall and by race/ethnicity. Subdistribution proportional hazards regression models, accounting for the competing risk of death, were used to calculate multivariable-adjusted hazard ratios (HRsd) for MI, stroke, and combined outcome.
Results Among 43,448 cases with prevalent SLE, 93.6% were female. Racial/ethnic breakdown was: 41% Black, 39% White, 15% Hispanic, 3% Asian, 1% Native American. Mean follow-up was 3.48 ± 2.86 years for all SLE patients. Overall crude rates were highest among Native Americans for MI, Blacks for stroke, and Native Americans for MI or stroke. Hispanics had the lowest overall crude rates for MI, stroke, and the combined outcome. After multivariable adjustment and accounting for the competing risk of death, Hispanics had lower MI risk (HRsd] 0.59 [95% CI: 0.42–0.84]) and Blacks had elevated risk of stroke (HRsd 1.36 [95% CI: 1.15–1.60]) as compared with Whites. For the outcome of MI or stroke, Blacks had an elevated risk (HRsd 1.22 [95% CI: 1.07–1.38], whereas Hispanics had a lower risk (HR 0.82 [95% CI: 0.67 to 0.99] compared to Whites.
Conclusions Marked race/ethnicity-specific variation exists in MI and stroke risks among Medicaid patients with SLE. Elevated CVD risks among Blacks and lower risks among Hispanics may account for some of the excess all-cause mortality observed among Black patients and lower overall mortality among Hispanics with SLE as previously described.
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