Fine particulate air pollution and cardiorespiratory effects in the elderly

Background: Past studies of air pollution effects among sensitive subgroups have produced inconsistent results. Our objective was to determine relationships between various measures of air pollution and cardiorespiratory effects in older subjects. Methods: We conducted a study that included repeated measurements of pulmonary function (arterial oxygen saturation) and cardiac function (heart rate and blood pressure) in a panel of 88 subjects (>57 years of age) in Seattle during the years 1999 to 2001. Subjects were healthy or had lung or heart disease. Each subject participated in sessions of 10 consecutive days of exposure monitoring and collection of health outcomes for up to 2 sessions. Associations between health outcomes and indoor, outdoor, and personal measures of particulate matter <= 2.5 micrometers (PM2.5) or particulate matter <= 10 micrometers (PM10) were evaluated using generalized estimating equations with an exchangeable working correlation matrix and robust standard errors. The model included terms for the within-subject, within-session effect; the within- subject, betweensession effect; and an interaction term for medication usage. The model controlled for temperature, relative humidity, body mass index, and age. Results: Associations between air pollution and health measurements were found primarily in healthy subjects. Healthy subjects taking no medications had decreases in heart rate associated with indoor and outdoor PM2.5 and PM10. Healthy subjects on medication had small increases in systolic blood pressure associated with indoor PM2.5 and outdoor PM10. Heterogeneity analysis found differences among the health groups for associations with particulate air pollution in heart rate but not in blood pressure. Conclusion: Modest concentrations of air pollutants were associated with small changes in cardiac function.