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Blacks with scleroderma exhibit more severe pulmonary disease
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Black patients with scleroderma demonstrate more severe pulmonary disease and higher unadjusted mortality compared with nonblack patients, according to data published in Arthritis Care & Research.
However, the researchers added that, when adjusted for socioeconomic factors, black race was not an independent factor for increased mortality. According to the researchers, lower median household income more accurately predicted increased mortality, independent of race. However, black patients had lower measures of socioeconomic status by all measured variables.
“While African-American patients with scleroderma have a distinct phenotypic and serologic profile, their experience of and outcomes in the disease may be confounded by socioeconomic factors that correlate with race,” Duncan F. Moore, MD, of MedStar Georgetown University Hospital, and colleagues wrote. “Within scleroderma cohorts, African-Americans have decreased educational attainment, increased Medicaid prevalence, decreased household income and decreased vehicle ownership relative to non–African-Americans.”
“Marital status, employment, educational attainment, insurance status and median income by household have all been examined as covariates in scleroderma mortality research,” they added. “Effect sizes have varied, and socioeconomic factors have not fully explained racial disparities in any studies to date.”
To evaluate the risks for severe disease and higher mortality among black patients, compared with nonblacks, with scleroderma, Moore and colleagues conducted a retrospective study of 402 participants seen between 2008 and 2016 at MedStar Georgetown University Hospital. Black and nonblack patients with scleroderma were matched by sex, age at first visit, date of first visit, disease duration at first visit and limited vs. diffuse cutaneous disease. The researchers also compared demographic, serologic and clinical features.
In addition, the researchers determined mortality risks using a Cox proportional hazards model, with covariates for race, marital status, education, employment, insurance and household income. Moore and colleagues imputed household income using patients’ zip code at first visit, based on U.S. Census data from 2006 to 2010. Among the participants, 202 were black. The 200 nonblack patients included 193 white patients, four Asian patients and three individuals that identified as “other.” Of the 12 patients who identified as Latino or Hispanic, 11 were non–black.
According to the researchers, black patients demonstrated more reduced forced vital capacity and diffusing capacity of the lungs for carbon monoxide compared with nonblacks, as well as more severe lung fibrosis, a higher prevalence of pulmonary hypertension and more severe cardiac involvement. In addition, there were statistical differences in the autoantibody profiles between the two groups. During the follow-up period, the mortality rate among blacks was 21%, compared with 11% in the nonblack group (P = .005).
Regarding mortality, black patients demonstrated an unadjusted hazard ratio for death of 2.061 (95% CI, 1.232-3.449) during follow-up. However, after adjusting for socioeconomic covariates, that figure was reduced to 1.256 (95% CI, 0.494-3.191). According to the researchers, only significant covariate associated with increased mortality was median income based on zip code, measured in tens of thousands of dollars (HR = 0.845; 95% CI, 0.723-0.986).
“We have re-demonstrated the unique clinical and serologic profile and increased morbidity and mortality of scleroderma in African-Americans, relative to non–African-Americans, in a large and previously undescribed cohort,” Moore and colleagues wrote. “In the US, race is largely a social construct, rather than a biological one, and it is confounded by relative economic deprivation. Thus, in robustly controlling for socioeconomic status, we have demonstrated a relatively diminished magnitude and significance of the mortality effect conferred by race. Nonetheless, race and ethnicity do correlate with differences in fibrosis-related gene expression and also with specific HLA haplotypes and SNPs.”
“Higher socioeconomic status may blunt the effects of intrinsic racial differences,” they added. “Regardless of the relative magnitudes of the contributory socioeconomic versus genetic factors, it is clear that African-Americans with scleroderma merit more intensive efforts to facilitate timely diagnosis and access to continued evaluation and suppressive treatment, particularly with respect to cardiopulmonary involvement.” – by Jason Laday
Disclosure: Moore reports no relevant financial disclosures. Please see the study for all other relevant financial disclosures.
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