A prior study established that concurrent poverty, persistent poverty, and exiting poverty were associated with the subsequent extent of damage accumulation in systemic lupus erythematosus (SLE). In this study, we examined whether concurrent poverty affects mortality after taking extent of damage accumulation into account.
Analyses were conducted on 807 persons with SLE participating in the University of California-San Francisco Lupus Outcomes Study in 2009, stratified by whether they lived in households with incomes ≤125% of the federal poverty level in that year. We used Cox proportional hazards regression to estimate the risk of mortality as a function of poverty status, with and without adjustment for demographics; lupus status, including extent of disease damage; overall health status; health behaviors; and health care characteristics.
Among 807 individuals interviewed in 2009, 71 (8.8%) had died by 2015, 57 (8.3%) among the nonpoor and 14 (12.1%) among the poor (P = 0.18). With adjustment only for age, poverty in 2009 was associated with an increased risk of mortality (hazard ratio [HR] 2.14 [95% confidence interval (95% CI) 1.18-3.88]) through 2015. However, after adjustment for extent of damage and age, poverty was no longer associated with an increased risk of mortality (HR 1.68 [95% CI 0.91-3.10]). Among those who died, those who were poor lived 13.9 fewer years (95% CI 6.9-20.8; P < 0.0001).
The principal way that poverty results in higher mortality in SLE is by increasing the extent of damage accumulation.