From the Journals

Poverty affects lupus mortality through damage accumulation



The extent of damage caused by lupus appears to be one of the strongest factors that contributes to the higher mortality observed in lupus patients who live in poverty, according to the results of a longitudinal cohort study of patients.

The findings from this analysis of participants in the Lupus Outcomes Study could potentially lead to solutions to reduce mortality of poor patients with systemic lupus erythematosus (SLE) through understanding why they have higher levels of disease damage, said first author Edward Yelin, PhD, of the Philip R. Lee Institute for Health Policy Studies at the University of California, San Francisco, and his colleagues at the university (Arthritis Care Res. 2017 Oct 3. doi: 10.1002/acr.23428).

Previous studies by the researchers have shown that concurrent and persistent poverty are associated with increased damage accumulation, and permanently exiting poverty reduces the level of accumulated damage. Studies by other groups have also revealed that some measures of low socioeconomic status contribute to elevated mortality in patients with SLE. But few studies have explored how poverty leads to increased mortality in SLE patients.

About two-thirds of the patients recruited for the Lupus Outcomes Study, which began in 2003, joined the study through nonclinical sources, such as public service announcements, patient support groups, and word of mouth; the remainder were recruited from academic and community clinical practices. The patients came from 37 states and from urban and rural areas. The investigators contacted participants in annual structured phone interviews that lasted about 45 minutes. The investigators defined poverty as household income at or below 125% of the federal poverty level because most participants were from high-cost urban areas.

The investigators had full information available for 807 of 814 who completed the annual survey in 2009, and these individuals made up the baseline sample for the mortality analysis through 2015. These 807 patients had a mean age of about 50 years and a disease duration of about 17 years; 93% were women, more than one-third were members of racial and ethnic minorities, and 14% met the study’s definition of poverty.

Poor individuals were more likely to be from a racial or ethnic minority (54% vs. 33%), to have a history of smoking (47% vs. 37%, to have a high school education or less (37% vs. 14%), to have never been married (36% vs. 15%), and to have a higher baseline level of disease damage as measured by score on the Brief Index of Lupus Damage (BILD; 2.8 vs. 2.2).

Overall, more poor individuals died during 2009-2015 (12.1% vs. 8.3%), but the difference was not significant. However, the poor died at a mean age of about 50, compared with 64 for individuals who were not poor. Adjustments for age showed that poverty, disease duration, BILD damage score, and having less than a high school education were all associated with higher mortality. But in a full multivariable analysis, only female gender (hazard ratio, 0.43; 95% confidence interval, 0.19-0.94), BILD damage score (1.17/point on 0-18 scale; 95% CI, 1.07-1.29), and physical health status (0.96/point; 95% CI, 0.94-0.98) were significant predictors of subsequent mortality risk, and poverty was no longer a significant predictor of mortality.

While poverty adjusted for age more than doubled the mortality risk (HR, 2.14; 95% CI, 1.18-3.88), much of the association could be attributed to the level of disease damage because once that variable was added to the analysis, poverty was no longer associated with an elevated mortality risk (HR, 1.68; 95% CI, 0.91-3.10). Furthermore, once the investigators took physical and mental health status into account, the risk of mortality associated with poverty was even smaller (HR, 1.20; 95% CI, 0.61-2.36).

“The present analysis indicates that prevention of accumulated damage will attenuate the mortality risk associated with poverty. We know that to achieve the goal of reduced damage requires good medical care in SLE, but that alone is insufficient since medical care accounts for only a small portion of the variance in damage accumulation between the poor and non-poor,” the investigators wrote. “Strategies to reduce disease damage must take into account the provision of high-quality care for the condition as well as the stress associated with poverty and living in neighborhoods with concentrated poverty.”

The research was supported by the Robert Wood Johnson Investigator in Health Policy Award and grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

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