Air pollution and doctors' house calls for respiratory diseases in the Greater Paris area (2000-3)

This study describes the short-term relationships between the daily levels of PM10, PM2.5, NO2 and the number of doctors' house calls for asthma, upper respiratory diseases (URD) and lower respiratory diseases (LRD) in Greater Paris for the years 2000 - 3. Doctors' house calls are a relevant health indicator for the study of short-term health effects of air pollution. Indeed, it is potentially more sensitive than indicators such as general hospital admissions due to the severity of diseases motivating the call. In this study, time-series analysis was used. The daily numbers of doctor's house calls were adjusted for time trends, seasonal factors, day of the week, influenza, weather and pollen. Up to 15 days of lag between exposure and health effects was considered using distributed lag models. A total of about 1 760 000 doctors' house calls for all causes occurred during the study period, among which 8027 were for asthma, 52 928 for LRD and 74 845 for URD. No significant increase in risk was found between air pollution and doctors' house calls for asthma. No significant association was found between NO2 and doctors' house calls. An increase of 10 mu g/m(3) in the mean levels of PM10 and PM2.5 encountered during the 3 previous days was associated with an increase of 3% (0.8% and 5.3%) and 5.9% (2.9% and 9.0%) in the number of doctor's house calls for URD and LRD, respectively. Considering up to 15 days between exposure and health outcomes, effects persist until 4 days after exposure and then decrease progressively. No morbidity displacement was observed. This study shows a significant heath effect of ambient particles (PM2.5 and PM10). When compared to the RRs obtained for mortality or hospital admissions in the same area, the values of the RRs obtained in this study confirm the higher sensibility of doctor's house calls for respiratory diseases as a health indicator.