CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Temporal relationship between air pollutants and hospital admissions for chronic obstructive pulmonary disease in Hong Kong

Fanny W S Ko¹, Wilson Tam², Tze Wai Wong³, Doris P S Chan¹, Alvin H Tung¹, Christopher K W Lai¹, David S C Hui¹

¹ Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
² Nethersole School of Nursing, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
³ Department of Community and Family Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong

Correspondence to:
Dr David S C Hui
Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, 30–32 Ngan Shing Street, Shatin, New Territories, Hong Kong; dschui{at}cuhk.edu.hk

Aims: To assess any relationship between the levels of ambient air pollutants and hospital admissions for chronic obstructive pulmonary disease (COPD) in Hong Kong.

Methods: A retrospective ecological study was undertaken. Data of daily emergency hospital admissions to 15 major hospitals in Hong Kong for COPD and indices of air pollutants (sulphur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃), particulates with an aerodynamic diameter of <10 µm (PM₁₀) and 2.5 µm (PM_2.5)) and meteorological variables from January 2000 to December 2004 were obtained from several government departments. Analysis was performed using generalised additive models with Poisson distribution, adjusted for the effects of time trend, season, other cyclical factors, temperature and humidity. Autocorrelation and overdispersion were corrected.

Results: Significant associations were found between hospital admissions for COPD with all five air pollutants. Relative risks for admission for every 10 µg/m³ increase in SO₂, NO₂, O₃, PM₁₀ and PM_2.5 were 1.007, 1.026, 1.034, 1.024 and 1.031, respectively, at a lag day ranging from lag 0 to cumulative lag 0–5. In a multipollutant model, O₃, SO₂ and PM_2.5 were significantly associated with increased admissions for COPD. SO₂, NO₂ and O₃ had a greater effect on COPD admissions in the cold season (December to March) than during the warm season.

Conclusion: Ambient concentrations of air pollutants have an adverse effect on hospital admissions for COPD in Hong Kong, especially during the winter season. This might be due to indoor exposure to outdoor pollution through open windows as central heating is not required in the mild winter. Measures to improve air quality are urgently needed.

Abbreviations: APHEA2, Air Pollution and Health: A European Approach 2; COPD, chronic obstructive pulmonary disease; NMMAPS, National Morbidity, Mortality, and Air Pollution Study; NO₂, nitrogen dioxide; O₃, ozone; PM₁₀, particulates with an aerodynamic diameter <10 µm; PM_2.5, particulates with an aerodynamic diameter <2.5 µm; SARS, severe acute respiratory syndrome; SO₂, sulphur dioxide

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