Burden of Serious Infections in Adults With Systemic Lupus Erythematosus: A National Population-Based Study, 1996-2011

Abstract

Objective: To compare rates of hospitalization for serious infections, trends in rates from 1996 to 2011, and in-hospital mortality between patients with systemic lupus erythematosus (SLE) and those without SLE in a national sample.

Methods: We analyzed hospitalizations for pneumonia, bacteremia/sepsis, urinary tract infections, skin infections, and opportunistic infections among adults in the Nationwide Inpatient Sample. We compared rates of hospitalization yearly among patients with SLE and the general population. We also computed odds ratios (ORs) for in-hospital mortality.

Results: In 1996, the estimated number of hospitalizations for pneumonia in patients with SLE was 4,382, followed by sepsis (2,305), skin infections (1,422), urinary tract infections (643), and opportunistic infections (370). Rates were much higher in patients with SLE than in those without SLE, with age-adjusted relative risks ranging from 5.7 (95% confidence interval [95% CI] 5.5-6.0) for pneumonia to 9.8 (95% CI 9.1-10.7) for urinary tract infection in 1996. Risks increased over time, so that by 2011, all relative risks exceeded 12.0. Overall risk of in-hospital mortality was higher in SLE only for opportunistic infections (adjusted OR 1.52 [95% CI 1.12-2.07]). However, in pneumonia and sepsis, mortality risks were higher in SLE among those who required mechanical ventilation.

Conclusion: Hospitalization rates for serious infections in SLE increased substantially between 1996 and 2011, reaching over 12 times higher than in patients without SLE in 2011. Reasons for this acceleration are unclear. In-hospital mortality was higher among patients with SLE and opportunistic infections and those with pneumonia or sepsis who required mechanical ventilation.

Figure 1

Rates of infectious hospitalizations by calendar year among adults age 18 years or older with systemic lupus erythematosus (a) and without systemic lupus erythematosus (b). Values are percents, age-adjusted to the 2000 Standard Population. Age-adjusted relative risks of hospitalization by type of infection and calendar year in patients with systemic lupus erythematosus compared to patients without systemic lupus erythematosus (c). Error bars are 95% confidence intervals. Error bars are very close to the point estimates in (b) and are difficult to appreciate.

Figure 2

Proportion of hospitalizations among adults age 18 years or older with systemic lupus erythematosus with in-hospital mortality, by type of infection and calendar year. Results are three-year moving averages, therefore values are missing for 1996 and 2011. Error bars are 95% confidence intervals. Mortality for urinary tract infection hospitalizations are not represented because these were rare.

Figure 3

Mortality risks in hospitalizations among adults age 18–64 years with or without systemic lupus erythematosus and nephritis hospitalized with pneumonia or sepsis (left) and subgroups with or without systemic lupus erythematosus who used mechanical ventilation among those hospitalized with pneumonia or sepsis (right). Values are odds ratios with 95% confidence intervals. The reference group in each case is that of hospitalizations among patients without systemic lupus erythematosus and without the clinical risk factor.