Chronic heart failure and risk of hospitalization with pneumonia: a population-based study.

BACKGROUND: Chronic heart failure may increase risk of pneumonia due to alveoli flooding and reduced microbial clearance. We examined whether chronic heart failure is a risk factor for pneumonia-related hospitalization.
METHODS: In this large population-based case-control study we identified adult patients with a first-time primary or secondary discharge diagnosis of viral or bacterial pneumonia between 1994 and 2008, using health care databases in Northern Denmark. For each case, ten sex- and age-matched population controls were selected from Denmark's Civil Registration System. We used conditional logistic regression to compute relative risk (RR) for pneumonia-related hospitalization among persons with and without pre-existing heart failure, overall and stratified by medical treatment. We controlled for a wide range of comorbidities, socioeconomic markers and immunosuppressive treatment.
RESULTS: The study included 67,162 patients with a pneumonia-related hospitalization and 671,620 population controls. The adjusted OR for pneumonia-related hospitalization among persons with previous heart failure was 1.81 (95% confidence interval (CI): 1.76-1.86) compared with other individuals. The adjusted pneumonia RR was lower for heart failure patients treated with thiazides only (adjusted OR=1.56, 95% CI: 1.46-1.67), as compared with patients whose treatment included loop-diuretics and digoxin as a marker of increased severity (adjusted OR=1.95, 95% CI: 1.85-2.06) or both loop-diuretics and spironolactone (adjusted OR=2.02, 95% CI: 1.90-2.15). The population-attributable risk of pneumonia hospitalizations caused by heart failure in our population was 6.2%.
CONCLUSIONS: Patients with chronic heart failure, in particular those using loop diuretics, have markedly increased risk of hospitalization with pneumonia.