A recent epidemiologic study of patients with systemic lupus erythematosus (SLE) investigated racial and ethnic differences in the risk for cardiovascular disease (CVD). Among SLE patients enrolled in Medicaid, the risk for myocardial infarction (MI) was lower in Hispanics and Asians compared with whites, and the risk of stroke was higher in blacks and Hispanics compared with whites.1
Explore this issueDecember 2017
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“The risk of CVD is known to be greatly elevated among SLE patients and is the major cause of death in SLE,” says Medha Barbhaiya, MD, MPH, an assistant attending physician at the Hospital for Special Surgery and an assistant professor at Weill Cornell Medical College in New York City. “It is also known that Hispanic, Asian and African Americans in the United States have higher incidence of SLE than whites, and often more severe disease. However, the role of patient race and ethnicity in relation to risk of CVD previously has not been well understood.”
The researchers used the Medicaid Analytic eXtract to identify patients between 18 and 65 years old with an SLE diagnosis and at least 12 months of continuous enrollment. The study ran from 2000–2010. The researchers followed the subjects from their SLE index date to their first CVD event, MI or stroke (if any), or death, disenrollment, loss to follow-up or end of the follow-up period. Of the 65,788 SLE patients enrolled, 93% were women, roughly 42% were black, 48% were white, 16% were Hispanic, 3% were Asian, and 1% were Native American/Alaskan Native. The mean follow-up time was 3.8 years.
CVD rates were highest among blacks, with an incidence rate (IR) of 10.57, and lowest among Asians, with an IR of 6.63. After multivariable adjustment, the risk of CVD events was elevated among blacks, with a hazard ratio (HR) of 1.14, compared with whites. When examining MI or stroke risk separately, Hispanics and Asians had a lower risk, with an HR of 0.61 and 0.57, respectively, compared with white SLE patients enrolled in Medicaid. Blacks and Hispanics had a higher risk for stroke than whites, with an HR of 1.31 and 1.22, respectively. Among all patients, the annual CVD event IR per 1,000 person-years measured 9.31. All rates came with a 95% CI.
The researchers also looked at a subgroup of patients with lupus-related nephritis. However, these results remained too underpowered to demonstrate an association in that group after multivariable adjustment.
“In this very large study of Medicaid SLE patients drawn from a nationwide sample, we found a 31% and 22% increased risk for stroke among black and Hispanic patients [respectively] when compared with white patients,” Dr. Barbhaiya says. “The risk of heart attack was lower among Hispanics and Asians (39% and 43%, respectively) and similar for blacks when compared with whites. Although blacks had increased rates of hypertension, and Asians as well as Hispanics had fewer CVD risk factors compared with whites, adjustment for these factors did not account for the risks demonstrated.”
Results Need Confirmation
Dr. Barbhaiya says these results must be confirmed in other data sets using other populations. Additionally, as a population-based study, its ability to address individual patient management remains limited.
However, this large, Medicaid-based study did include SLE patients of multiple races and ethnicities, and it reveals demographic differences in CVD risks among SLE patients that clinicians should know about.
“The results go against current thinking, but are largely consistent with studies in the general population showing a Hispanic and Asian paradox,” Dr. Barbhaiya says. “It is currently not clear whether there is some protective element … causing them to not have as many strokes and MIs, or whether this is an epidemiologic association. However, this is the first time it has been shown in SLE.”
In contrast, African Americans have increased CVD risk factors, leading to more heart disease. The higher event rates in this group indicate SLE may result in an additional disease burden.
“If the MI risk [difference] is confirmed, this may suggest certain races/ethnicities could undergo earlier screening and aggressive risk factor management,” says Dr. Barbhaiya. “Additionally, we did not look at age stratification in this study. Further research is needed to determine whether, for example, we should be screening for hypertension and cholesterol in younger blacks with SLE than suggested by current guidelines.”
The fact the study worked with such a large data sample—a decade of data on more than 65,000 SLE patients—bolsters its results. Sociodemographic factors, as well as CVD- and SLE-specific comorbidities, were available in the claims data. This allowed the researchers to fit several models looking for confounders and mediators that might have contributed to increased CVD deaths in these patients.
They did note there are limitations inherent in using Medicaid data, including using administrative case definitions to identify SLE prevalence and potential misclassifications of race/ethnicity. The researchers also couldn’t examine risks among those 65 years or older given dual enrollment in Medicare.
Look at Underlying Mechanism?
Dr. Barbhaiya says further research must look at underlying mechanisms to better understand how to best address these findings. For example, is there a genetic component or perhaps biomarker differences doctors could exploit? Until these questions are answered, how to intervene remains an open question.
“Increased understanding of how race and ethnicity in SLE influence cardiac disease risk may help us improve prevention strategies,” she says. “The goal is to identify patients at higher risk for cardiovascular disease early and enhance the management of CVD among SLE patients.”
Kurt Ullman has been a freelance writer for more than 30 years and a contributing writer to The Rheumatologist for 10 years.
- Barbhaiya M, Feldman CH, Guan H, et al. Race/ethnicity and cardiovascular events among patients with systemic lupus erythematosus. Arthritis Rheumatol. 2017 Sep;69(9):1823–1831.