National Cost of Hospitalization for Legionnaires' Disease, 2001 - 2009

BACKGROUND:   The crude national incidence of Legionnaires’ disease (LD) increased 192% from 2000 – 2009 (0.39 to 1.15 per 100,000 population) with 8,000 – 18,000 hospitalizations annually. With an increase in the burden of LD and an aging population it is important to identify risk factors and associated hospitalization costs.

METHODS:   Analysis was conducted using Nationwide Inpatient Sample (NIS) data, Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, the largest all-payer inpatient care hospital discharge database publicly available in the US NIS is sampled to approximate a 20% stratified sample of US community hospitals and weighted to obtain national estimates. Data was restricted to individuals with an ICD-9 discharge code for LD (482.84) from 2001 – 2009. US Census data were utilized to calculate incidence. To assess illness severity, four mutually exclusive severity categories were created using procedure codes and an outcome variable (live/dead). Generalized linear models (GLM) were utilized to identify risk factors associated with disease severity, cost, and length of stay (LOS). Economic data was adjusted to 2011 US dollar values. Cost estimates do not include prescription information.

RESULTS:   From 2001 – 2009, an estimated 25,147 records contained a LD discharge code, with the annual incidence increasing steadily (0.58 to 1.48 per 100,000 population) and the percentage of deaths decreasing (10.4% in 2001 to 7.5% in 2009). The annual average LD LOS ranged from 10.9 – 12.8 days. LD hospitalization costs exceeded $716 million; with average cost per hospitalization ranging from $25,375 – $30,625. When analyzed from the lowest severity category (1) to highest (4), average LOS and cost per stay ranged from 7.5 – 25.1 days and $13,053 - $71,318, respectively. Age, alcohol abuse, deficiency anemias, congestive heart failure (CHF), coagulation deficiency, metabolic disorders, neurologic disorders, paralysis, and renal failure (RF) were significant risk factors for severe outcome. Disease severity, age, CHF, coagulation deficiency, diabetes complications, metabolic disorders, paralysis, RF, region, and insurance type were associated with increased LOS and cost.

CONCLUSIONS:   Although analysis did not include prescription and post-discharge cost, hospitalizations for LD carry a significant economic cost. Furthermore, several demographic variables and chronic conditions associated with disease severity, LOS and cost were identified. With the national LD incidence increasing yearly, total annual cost can be expected to rise. More focus should be placed on vulnerable populations to prevent LD and the progression to severe disease.