Association between air pollution and general practitioner visits for respiratory diseases in Hong Kong.

BACKGROUND Few studies have explored the relation between air pollution and general practitioner (GP) consultations in Asia. Clinic attendance data from a network of GPs were studied, and the relationship between daily GP consultations for upper respiratory tract infections (URTI) and non-URTI respiratory diseases and daily air pollutant concentrations measured in their respective districts was examined. METHODS A time series study was performed in 2000-2002 using data on daily patient consultations in 13 GP clinics distributed over eight districts. A Poisson regression model was constructed using the generalised additive model approach for each GP clinic, and associations with daily numbers of first visits for URTI were sought for daily concentrations of the following air pollutants: SO(2), NO(2), O(3), PM(10,) and PM(2.5). A summary relative risk of first visits to the GP for URTI per unit increase in concentration for each air pollutant was derived using a random effect model. First visits for non-URTI respiratory diseases were analysed in three GP clinics. RESULTS Significant associations were observed between first visits for URTI and an increase in the concentrations of NO(2), O(3), PM(10), and PM(2.5). The excess risk was highest for NO(2) (3.0%), followed by O(3) (2.5%), PM(2.5) (2.1%), and PM(10) (2.0%). Similar associations with these air pollutants were found for non-URTI respiratory diseases. CONCLUSIONS These results provide further evidence that air pollution contributes to GP visits for URTI and non-URTI respiratory diseases in the community.