'It makes a difference where you live': Lupus nephritis mortality highest in central metros
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Race and residence are both independently associated with lupus nephritis mortality, with Black patients and those living in large central metropolitan areas demonstrating the highest rates, according to data presented at ACR Convergence 2021.
In addition, the data revealed an “upward trend” in lupus nephritis mortality overall during the past 5 years, noted presenter Ram Singh, MD, of the University of California, Los Angeles, David Geffen School of Medicine.
“Lupus nephritis affects 50-80% of childhood-onset, and about 50% of adult, systemic lupus erythematosus,” Singh told attendees at the virtual meeting. “End-stage renal disease due to lupus nephritis portends a high premature death burden, compared to other manifestation of SLE — up to 26 times higher.
“Lupus nephritis-associated end-stage renal disease was shown to double the risk for hospital mortality versus all-case end-stage renal disease,” he added. “In a U.S. registry of lupus nephritis-related ESRD from 1995 to 2014, all-cause mortality reduced in recent years in all race and ethnic groups, but the mortality disparity did not change.”
To examine lupus nephritis mortality trends in the United States from 1999 to 2019, and identify population characteristics associated with mortality, Singh and colleagues studied the CDC WONDER database. According to the researchers, WONDER compiles mortality data using death certificates from all 50 states and Washington, D.C. The researchers obtained death counts attributed to SLE and lupus nephritis, and analyzed them as a whole, as well as based on race, ethnicity and urbanization level.
Race and ethnicity data included Hispanic, non-Hispanic white, non-Hispanic Black, non-Hispanic American Indian or Alaska Native, and non-Hispanic Asian or Pacific Islander patients. Meanwhile, urbanization was defined using 2006 data and grouped based on population size. Categories included large central metropolitan, large fringe metropolitan, medium metropolitan, small metropolitan, micropolitan and non-metropolitan. Using all of this data, Singh and colleagues calculated age-standardized mortality rates, per 100,000 persons, for lupus nephritis in each year from 1999 to 2019.
Their analyses also included a joinpoint regression to fit piecewise-linear trends to yearly lupus nephritis age-adjusted mortality rates, as well as those in patients with SLE for comparison.
According to the researchers, there were 8,899 deaths attributed to lupus nephritis, and 25,973 deaths due to SLE, from 1999 to 2019. Overall, the age-adjusted mortality rate for lupus nephritis decreased 27.2% over the 21-year period. However, a more detailed analysis suggested a wrinkle. Based on the joinpoint trends, the age-adjusted mortality rate for lupus nephritis decreased from 1999 to 2009, plateaued between 2009 and 2012, decreased again from 2012 to 2015, before significantly increasing from 2015 (0.1) to 2019 (0.12).
Meanwhile, the age-adjusted morality rate for SLE continuously decreased, without the ups and downs demonstrated in lupus nephritis, from 1999 through 2019.
According to Singh and colleagues, Black patients were “profoundly overrepresented” in lupus nephritis deaths, accounting for 38% despite representing only 12.8% of U.S. population. Meanwhile, white patients, who make up 65.4% of U.S. population, represented 41.5% of all deaths attributed to lupus nephritis. In addition, the age-adjusted mortality rate for lupus nephritis in Black individuals was sixfold higher than in white persons, and more than twofold higher than in all other race or ethnic groups.
The age-adjusted lupus nephritis mortality rate was also significantly higher in Hispanic, American Indian or Alaska Natives, and Asian or Pacific Islander patients, compared with whites.
Regarding residency, although 29.6% of the U.S. population lived in large central metro area, they accounted for 35.1% of lupus nephritis deaths. The age-adjusted mortality rate for lupus nephritis was highest in large central metro areas (P < .05 relative to all others), followed by medium metro, small metro, micropolitan and nonmetro areas.
“Lupus nephritis mortality decreased from 1999 to 2015, however, there is an upward trend in the last 5 years,” Singh said. “Both race/ethnicity and residence independently were associated with lupus nephritis mortality. Lupus nephritis mortality is highest in Black persons and residents in large central metros, relative to the respective reference groups.”
“Urbanization is an effective modifier of race/ethnicity’s effect on lupus nephritis mortality, suggesting neighborhood environmental factors on health outcomes — residence in a large central metro increased the risk, whereas living in a large fringe metro was generally protective,” he added. “Urbanization had no effect on lupus nephritis mortality risk in Black persons. However, in subsequent analyses, when we included other variables, we find some increase in mortality in large fringe metro areas. It makes a difference where we live, because it can impact health and mortality beyond individual race and ethnic factors.”
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Singh R. Abstract 0454. Presented at: ACR Convergence 2021; November 5-9, 2021 (virtual meeting).
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