Rationale: Little is known about the long-term effects of air pollution on pneumonia hospitalization in the elderly.
Objectives: To assess the effect of long-term exposure to ambient nitrogen dioxide, sulfur dioxide, and fine particulate matter with diameter equal to or smaller than 2.5 microm (PM(2.5)) on hospitalization for community-acquired pneumonia in older adults.
Methods: We used a population-based case-control study in Hamilton, Ontario, Canada. We enrolled 345 hospitalized patients aged 65 years or more for community-acquired pneumonia and 494 control participants, aged 65 years and more, randomly selected from the same community as cases from July 2003 to April 2005. Health data were collected by personal interview. Annual average levels of nitrogen dioxide, sulfur dioxide, and PM(2.5) before the study period were estimated at the residential addresses of participants by inverse distance weighting, bicubic splined and land use regression methods and merged with participants' health data.
Measurements and main results: Long-term exposure to higher levels of nitrogen dioxide and PM(2.5) was significantly associated with hospitalization for community-acquired pneumonia (odds ratio [OR], 2.30; 95% confidence interval [CI], 1.25 to 4.21; P = 0.007 and OR, 2.26; 95% CI, 1.20 to 4.24; P = 0.012, respectively, over the 5th-95th percentile range increase of exposure). Sulfur dioxide did not appear to have any association (OR, 0.97; 95% CI, 0.59 to 1.61; P = 0.918). Results were somewhat sensitive to the choice of methods used to estimate air pollutant levels at residential addresses, although all risks from nitrogen dioxide and PM(2.5) exposure were positive and generally significant.
Conclusions: In older adults, exposure to ambient nitrogen dioxide and PM(2.5) was associated with hospitalization for community-acquired pneumonia.