Significant Reductions in Mortality in Hospitalized Patients with Systemic Lupus Erythematosus in Washington State from 2003 to 2011

Abstract

Background: Systemic lupus erythematosus (SLE or lupus) is an autoimmune multisystem disease. While a complete understanding of lupus' origins, mechanisms, and progression is not yet available, a number of studies have demonstrated correlations between disease prevalence and severity, gender, and race. There have been few population based studies in the United States.

Objectives: To assess temporal changes in demographics and hospital mortality of patients with lupus in Washington State from 2003 to 2011.

Study design: This study used data from the Healthcare Cost and Utilization Project (HCUP), a patient information database, and data from the Washington State census to study a group of patients in the state. Lupus hospitalizations were defined as any hospitalization with an ICD-9-CM diagnosis code for systemic lupus erythematosus. Regression analysis was used to assess the effect of calendar time on demographics and hospital outcomes.

Results: There were a total of 18,905 patients in this study with a diagnostic code for lupus. The mean age of the group was 51.5 years (95% CI: 50.6-52.3) in 2003 and 51.3 years (95% CI: 50.6-52.0) in 2011. The population was 88.6% female. Blacks were 2.8 times more likely to have a lupus hospitalization than whites when compared to the Washington population. While hospital mortality decreased during this eight year period (3.12% in 2003 to 1.28% in 2011, p=0.001) hospital length of stay remained statistically unchanged at an average of 4.9 days during that eight year period. We found a significant decrease in annual hospital mortality over the study period [odds ratio(OR): 0.92 per year, 95% CI 0.88-0.96, P<0.001]. Hospital mortality was higher in males (2.6% male death to 1.8% female death).

Conclusions: In this large group of hospitalized lupus patients in Washington, hospital length of stay remained relatively stable over time but hospital mortality decreased by over 50% over the eight year study period.

Fig 1. Prevalence of lupus hospitalizations by race based on Washington State population estimates, 2008 through 2011.

Fig 2. Prevalence of lupus hospitalizations in Hispanics and non-Hispanics based on Washington State population estimates, 2008 through 2011.