The burden and etiology of community-onset pneumonia in the aging Japanese population: a multicenter prospective study

Abstract

Background: The increasing burden of pneumonia in adults is an emerging health issue in the era of global population aging. This study was conducted to elucidate the burden of community-onset pneumonia (COP) and its etiologic fractions in Japan, the world's most aged society.

Methods: A multicenter prospective surveillance for COP was conducted from September 2011 to January 2013 in Japan. All pneumonia patients aged ≥ 15 years, including those with community-acquired pneumonia (CAP) and health care-associated pneumonia (HCAP), were enrolled at four community hospitals on four major islands. The COP burden was estimated based on the surveillance data and national statistics.

Results: A total of 1,772 COP episodes out of 932,080 hospital visits were enrolled during the surveillance. The estimated overall incidence rates of adult COP, hospitalization, and in-hospital death were 16.9 (95% confidence interval, 13.6 to 20.9), 5.3 (4.5 to 6.2), and 0.7 (0.6 to 0.8) per 1,000 person-years (PY), respectively. The incidence rates sharply increased with age; the incidence in people aged ≥ 85 years was 10-fold higher than that in people aged 15-64 years. The estimated annual number of adult COP cases in the entire Japanese population was 1,880,000, and 69.4% were aged ≥ 65 years. Aspiration-associated pneumonia (630,000) was the leading etiologic category, followed by Streptococcus pneumoniae-associated pneumonia (530,000), Haemophilus influenzae-associated pneumonia (420,000), and respiratory virus-associated pneumonia (420,000), including influenza-associated pneumonia (30,000).

Conclusions: A substantial portion of the COP burden occurs among elderly members of the Japanese adult population. In addition to the introduction of effective vaccines for S. pneumoniae and influenza, multidimensional approaches are needed to reduce the pneumonia burden in an aging society.

Fig 1. Annual incidences of community-onset pneumonia per 1,000 people by age group and gender.

The incidence among the male population is shown as a solid line, and the incidence among the female population is shown as a dashed line. The 95% confidence intervals for each point are shown as vertical lines.

Fig 2. Estimated annual burden of community-onset pneumonia in Japanese adults by clinical and etiological category, 2012.

CAP = community-acquired pneumonia; CI = confidence interval; HCAP = health care-associated pneumonia; HI = H. influenzae; PDR = potentially drug-resistant; RV = respiratory virus; SP = S. pneumoniae. Maximum estimates are shown for SP- and HI-associated pneumonia.