Original article
Chronic heart failure and risk of hospitalization with pneumonia: A population-based study

https://doi.org/10.1016/j.ejim.2013.02.013Get rights and content

Abstract

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.

Introduction

Hospitalizations with pneumonia have increased by up to 50% in Western populations during the past 15 years [1], [2], [3], and pneumonia is a leading cause of death [4], [5], [6]. The prevalence of many chronic diseases has increased because of lifestyle factors, population aging, and longer disease survival [7]. This increase is expected to contribute to a further rise in pneumonia hospitalizations, both in the Western world [8] and in developing countries [9].

Chronic heart failure may be a major risk factor for hospitalization with pneumonia, yet population-based studies on this association are few [10], [11], [12], [13], [14], [15]. Persons with heart failure may have increased susceptibility to severe pneumonia for several reasons [8]. Alveoli flooding may interfere with normal physiological mechanisms operating in the alveolar lining fluid at the interphase between air and the lung tissue (including effective opsonins and macrophages), thus hampering microbial clearance and increasing the risk of bacterial infection [16]. Also, pneumonia may induce or worsen heart failure and cardiogenic pulmonary edema as cardiac output fails to meet the needs during infection, increasing the risk of being hospitalized with pneumonia [1].

A few cohort and case–control studies have included heart failure on a list of predictors for pneumonia, with widely varying relative risk estimates between 1.5 and 3.8 [11], [12], [13], [17]. Studies on the effect of the severity of heart failure on the risk of pneumonia are, to our knowledge, absent. Bearing in mind that pre-existing heart failure increases risk of death following pneumonia by 30–50% [8], [18], [19], it is important to investigate heart failure as risk factor for pneumonia and to clarify which patients are at particularly increased risk. We undertook a large population-based case–control study to assess these associations.

Section snippets

Materials and methods

We conducted this study in the Danish counties of North Jutland and Aarhus, with a mixed rural and urban population of approximately 1.15 million people. The Danish National Health service provides tax-supported health care for all residents, including free access to primary care and hospitals, and reimbursement of a portion of the cost of most prescription drugs [20]. Civil registration numbers, unique identifiers assigned to each Danish citizen, which encode birth date and sex, allow accurate

Descriptive data

We identified 67,162 patients with a first incident pneumonia-related hospitalization and 671,620 population controls (Table 1). The study population was 53% male and 47% female, with a median age of 73 (interquartile range 60 to 81) years. A total of 12,339 pneumonia cases (18.4%) and 53,989 controls (8.0%) had a previous diagnosis of heart failure. Compared with their age-matched population controls, pneumonia cases were much more likely to have a history of any hospital-diagnosed comorbidity

Discussion

Our large population based study of more than 67,000 patients with pneumonia provides robust evidence that patients with chronic heart failure have an almost doubled risk of hospitalization with pneumonia compared with other individuals. Heart failure patients with cardiomyopathy and heart valve disease and those who used loop-diuretics for therapy were at particularly increased risk.

The results of our population-based study are consistent with previous observations of increased risk of

Learning points

  • In a large and unselected population of all ages, patients with chronic heart failure had an almost doubled risk of hospitalization with pneumonia, compared with other individuals.

  • Patient use of loop-diuretics, and the presence of cardiomyopathy or heart valve disease are predictors of particularly increased pneumonia risk.

  • Clinicians should remain vigilant for the risk of pneumonia in heart failure patients, and further studies should elucidate modifiable risk factors for pneumonia in this

Funding source

This study was supported by the Karen Elise Jensen Foundation and the Clinical Epidemiological Research Foundation, Denmark. The Department of Clinical Epidemiology is a member of the Danish Centre for Strategic Research in Type 2 Diabetes (the Danish Research Council, grant nos. 09-075724 and 10-079102).

Conflict of interests

None of the authors received any fees, honoraria, grants or consultancies that would constitute a conflict of interest with the current study. The Department of Clinical Epidemiology, Aarhus University Hospital, receives funding for other studies from companies in the form of research grants to (and administered by) Aarhus University; none of these studies has any relation to the present study.

Ethics approval

As this study did not involve any contact with patients or any intervention, according to Danish law it was not necessary to obtain permission from the Danish Scientific Ethical Committee.

Acknowledgments

None.

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