Prolonged exposure to higher levels of pollutants can lead to hospitalization for pneumonia

A McMaster University researcher has found the first evidence that prolonged exposure to higher levels of the pollutants found in car exhaust fumes and industrial air pollution can lead to hospitalization for pneumonia in adults aged 65 and older.

Infectious disease specialist Mark Loeb led a research team to assess the effect of long-term exposure to nitrogen dioxide and sulfur dioxide, both found in motor vehicle emissions, and fine particulate matter, found in industrial air pollution, on the risk of hospitalization for pneumonia in older adults. Loeb, a physician, is a professor in the Department of Pathology and Molecular Medicine and the Department of Clinical Epidemiology and Biostatistics of the Michael G. DeGroote School of Medicine.

The research results are to be published in the Jan. 1, 2010, issue of the American Journal of Respiratory and Critical Care Medicine.

"Our study found that among older individuals, long-term exposure to traffic pollution independently increased their risk of hospitalization for pneumonia," said Loeb, who is also the director of the Infectious Diseases Division at McMaster University. "We propose that exposure to air pollution may have increased the individuals' susceptibility to pneumonia by interfering with lung immune defenses designed to protect the lung from pathogens."

Loeb led a research team in recruiting 365 older adults from Hamilton who had been hospitalized with radiologically confirmed pneumonia between July 2003 and April 2005. Control subjects randomly selected from the same neighbourhoods as the patients were also enrolled in the study.

The research team used structured interviews to collect health data from participants and compared the two groups' exposures to nitrogen dioxide, sulfur dioxide and fine particulate matter of less than 2.5 micrometres using data from air-quality monitoring stations and land-use regression models.

The researchers found that exposure for more than 12 months to higher levels of nitrogen dioxide and fine particulate matter of less than 2.5 micrometres more than doubled the risk of hospitalization for pneumonia in adults aged 65 and older. Exposure to sulfur dioxide was not associated with an increased risk of hospitalization.

"The results of this study highlight the important health impact that long-term exposure to ambient air pollution can have on respiratory infections," Loeb said. "It also emphasizes the need to monitor emissions from vehicles, given that ground-level nitrogen dioxide is derived predominantly from traffic."

Pneumonia is a leading cause of illness and death in order adults. Rates of hospitalization for pneumonia among patients 65 year and older have increased in recent years. While the role of air pollution has been recognized as a risk factor for asthma and other respiratory diseases, few studies have been completed on the role of air pollution on pneumonia hospitalization in older adults.