DIFFERENCE IN THE EFFECT OF COARSE PARTICULATE MATTER ON FIRST, SECOND AND OVERALL ADMISSIONS FOR RESPIRATORY DISEASE AMONG THE ELDERLY IN VANCOUVER, CANADA

Abstract

ISEE-107 Purpose: To examine the difference in the effect of particulate matter on first, second, and overall hospital admissions for respiratory disease among the elderly. Methods: We studied 8,989 adults 65 years of age or older living in greater Vancouver, who were admitted to hospital for any acute respiratory disease (ICD-9 codes 460–519) during the period from June 1, 1995 to March 31, 1999. Time-series analysis was used to evaluate the association between respiratory admissions and daily measures of particulate matter (PM10, PM2.5 and PM10–2.5) after adjustment for gaseous pollutants (CO, O3, NO2 and SO2) and meteorological variables. Results: Repeated admissions for respiratory disease were common among the elderly. Approximately 30 percent of the subjects were readmitted to hospital, and 9% had more than two admissions for respiratory disease during the 4-year study period. PM10–2.5 was significantly associated with the second and overall admissions for respiratory disease, but not with the first admission. The adjusted relative risks for an increment of 4.2 μg/m3 in 3-day average PM10–2.5 concentrations were 1.03 (95% confidence interval: 0.98–1.09) for first admission, 1.22 (1.10–1.36) for second admission, and 1.06 (1.02, 1.11) for overall admissions. There was no significant effect of PM2.5 on hospital admissions for respiratory disease among the elderly. Conclusions: Our data suggest that: 1) coarse particulate matter may be associated with exacerbations of respiratory conditions, rather than disease induction; 2) analysis based on overall hospital admissions tends to provide conservative relative risk estimates; and 3) PM10–2.5 has a larger effect on respiratory admissions than PM2.5.