An evaluation of the air quality health index program on respiratory diseases in Hong Kong: An interrupted time series analysis

Background: On December 30th, 2013, the Hong Kong government implemented the Air Quality Health Index (AQHI) alert programme warnings designed to reduce short-term effects of air pollution on population health. However, whether air quality alert programme warnings, such as the AQHI, reduce morbidity is still questionable. Using a quasi-experimental design, we conducted the first evaluation of the AQHI in Hong Kong focusing on respiratory morbidity. Method: Interrupted time series with Poisson segmented regression from 2010 to 2016 was used to detect any sudden or gradual changes in emergency respiratory hospital admissions, adjusted for air pollutants (NO2, SO2, PM10, O-3), temperature and humidity, when the AQHI policy was implemented. The findings were validated using three false policy study periods and digestive diseases as a control. We also assessed effects on specific respiratory diseases (respiratory tract infections (RTI), asthma, chronic obstructive pulmonary disease and pneumonia) and by age. Results: From January 1st' 2010 to December 31st, 2016, 10576.98 deseasonalized, age-standardized hospital admissions for respiratory disease occurred in Hong Kong. On implementation of the AQHI, RTI admissions immediately dropped by 14% (relative risk (RR) 0.86 95% confidence interval (CI) 0.76-0.98). In age specific analysis, immediate reductions in hospital admissions were only apparent in children for RTI (RR 0.84, 95% CI 0.74-0.96) and pneumonia (RR 0.88, 95% CI 0.60-0.96). Conclusion: Hong Kong's AQHI helped reduced hospital admissions in children, particularly for RTI and pneumonia. To maximize health benefits of the policy, at risk groups need to be able to follow the behavioral changes recommended by the AQHI warnings.