The temporal relationship between air pollutants and hospital admissions for chronic obstructive pulmonary disease in Hong Kong.

Abstract

Aims: To assess any relationship between the levels of ambient air pollutants and the hospitalization rate due to chronic obstructive pulmonary disease (COPD) in Hong Kong. Methods: This is a retrospective ecological study. Data of daily emergency hospital admissions to 15 major hospitals in Hong Kong for COPD and indices of air pollutants (sulphur dioxide [SO2], nitrogen dioxides [NO2], ozone [O3], particulates with an aerodynamic diameter of less than 10μg/m3 [PM10] and 2.5μg/m3 [PM2.5]) and meteorological variables from January 2000 to December 2004 were obtained from several government departments. Analysis was performed by the generalized additive models with Poisson distribution. The effects of time trend, season, other cyclical factors, temperature, and humidity were adjusted. Autocorrelation and overdispersion were corrected. Results: Significant associations were found between hospital admissions for COPD with all 5 air pollutants. Relative risks for admission for every 10μg/m3 increase in SO2, NO2, O3, PM10 and PM2.5 were 1.007, 1.026, 1.034, 1.024 and 1.031 respectively, at a lag day ranged from lag 0 to cumulative lag 0-5. In a multi-pollutant model, O3, SO2 and PM2.5 were significantly associated with increased admissions for COPD. SO2, NO2, and O3 had a stronger effect on COPD admissions in the cold season (December to March) than during the warm season. Conclusion: Adverse effects of ambient concentrations of air pollutants on hospitalization rates for COPD are evident, especially during the winter season in Hong Kong. This might be due to indoor exposure to outdoor pollution through opened windows as central heating is not required in our mild winter. Measures to improve air quality are urgently needed.