Marked reduction in 30-day mortality among elderly patients with community-acquired pneumonia

Abstract

Background: Community-acquired pneumonia is the most common infectious cause of death in the US. Over the last 2 decades, patient characteristics and clinical care have changed. To understand the impact of these changes, we quantified incidence and mortality trends among elderly adults.

Methods: We used Medicare claims to identify episodes of pneumonia, based on a validated combination of diagnosis codes. Comorbidities were ascertained using the diagnosis codes located on a 1-year look back. Trends in patient characteristics and site of care were compared. The association between year of pneumonia episode and 30-day mortality was then evaluated by logistic regression, with adjustment for age, sex, and comorbidities.

Results: We identified 2,654,955 cases of pneumonia from 1987-2005. During this period, the proportion treated as inpatients decreased, the proportion aged ≥80 years increased, and the frequency of many comorbidities rose. Adjusted incidence increased to 3096 episodes per 100,000 population in 1999, with some decrease thereafter. Age/sex-adjusted mortality decreased from 13.5% to 9.7%, a relative reduction of 28.1%. Compared with 1987, the risk of mortality decreased through 2005 (adjusted odds ratio, 0.46; 95% confidence interval, 0.44-0.47). This result was robust to a restriction on comorbid diagnoses assessing for the results' sensitivity to increased coding.

Conclusions: These findings show a marked mortality reduction over time in community-acquired pneumonia patients. We hypothesize that increased pneumococcal and influenza vaccination rates as well as wider use of guideline-concordant antibiotics explain a large portion of this trend.

Figure 1

Standarized incidence of community-acquired pneumonia among elderly adults. Trends for men and women are standardized for age. Trends for the combined sample are standardized to the sex and age distribution of the elderly Medicare population in the year 2000.

Figure 2

Trends in the frequency of selected comorbid conditions among inpatients and outpatients diagnosed with community-acquired pneumonia. CHF denotes congestive heart failure; DM denotes diabetes mellitus.

Figure 3

Adjusted 30-day mortality rates among elderly patients diagnosed with community-acquired pneumonia. Mortality rates are standardized to the sex and age distribution of year 2000.

Figure 4

Multivariate-adjusted mortality trends. DM denotes diabetes mellitus. This figure shows the odds ratio of death 30 days after a diagnosis of community-acquired pneumonia in each year relative to reference year 1987.