Time-series studies for daily mortality and hospital admissions: Interaction between

1. HEI – Public Health and Air Pollution in Asia (PAPA) Project Time-series studies for daily mortality and hospital admissions: Interaction between air pollution and respiratory viruses (Hong Kong Study) CM Wong1 , JSM Peiris2, TQ Thach1, PYK Chau1 KP Chan1 , GN Thomas1, TW Wong3,TH Lam1, AJ Hedley1, 1 Department of Community Medicine and 2 Department of Microbiology, The University of Hong Kong 3 Department of Family & Community Medicine, The Chinese University of Hong Kong

2. Background Hong Kong • Located in a sub-tropical region with average temperature 24oC (range 11-34) and relative humidity 78% (range 45-95) • Population 6.8 million in 1092 km2 in urban and rural areas • Primary care: 85% private practitioners • Hospital care: 94% in public hospitals • Computerized mortality and hospital information systems

3. The problems of air pollution arise mainly from burning fossil fuels.

4. In the past 15 years NO2 and O3 were on the increase while PM10 was relatively stable, and SO2 levels remained low after implementation of sulphur restriction regulations in 1990 and in subsequent years.

5. The University of Hong Kong Department of Community Medicine since 1989 has carried out a series of air population and health studies, including • Cross-sectional studies on children respiratory symptoms • Bronchial responsiveness in children exposed to atmospheric pollution • Respiratory health of primary school children • Health benefit of the 1990 sulphur restriction intervention • Cardiorespiratory and all-cause mortality after the restrictions • Comparison between two districts of the effects of an air pollution intervention on bronchial responsiveness in primary school children • Effects of an ambient air pollution intervention and environmental tobacco smoke on children's respiratory health • Daily time-series studies on mortality and morbidity • Effects of air pollution on hospital admissions in Hong Kong and London compared • Effect of air pollution on daily mortality

6. PAPA Project Hong Kong, Bangkok, Shanghai and Wuhan were selected in the 1st phase. While all cities are to perform time-series studies on mortality, Hong Kong will also study effects of air pollution on hospitalization. • Average 30,000 deaths per year, including 26% cardiovascular and 19% respiratory. • Average 1.3 million hospital admissions, including 8% cardiovascular and 11% respiratory.

7. Daily counts of health outcome will be modeled by Poisson regression with adjustment for seasonality, trend and covariates. Temperature, Humidity, Holidays

8. Daily air pollutants will then be assessed in the model after the adjustment. • Hourly data in each monitoring station • Definition: 8 hourly mean of O3; 24 hourly mean of SO2, NO2 & PM10 • Missing data: < 75% of hourly data

9. In addition, the Hong Kong team will assess the effects of air pollution and influenza, as well as interaction between these two agents on mortality and morbidity. –Identification of epidemics based on virological data

10. General Air Quality Monitoring Station General Air Quality Monitoring Station employed in this study Roadside Air Quality Monitoring Station Progress We had visited all 8 air pollutant monitoring stations to be used in the study.

11. The surrounding environments are representative of the living environments of Hong Kong with residential areas close to commercial complexes and traffic routes. Picture of Kwun Tong site

12. We collected documents for site selection criteria, data processing policy and procedure, data validation and performance audit procedure from the Environmental Protection Department.

13. We obtained an outline of data collection and quality control for isolation of respiratory viruses.

14. We assessed the procedure in retrieving data for death from the Death Registry, Department of Health and Census & Statistics Department.

15. Clinical data are captured in real time by a Clinical Management System. After the accuracy and coverage of the Clinical Data Format were assessed to be satisfactory in an ad hoc study, the system was extended to all major public hospitals.

16. All the data for year 1996-2002 have been collected and are ready for analysis. Air pollutants: NO2, SO2, PM10 and O 3 Mortality: All natural causes, Cardio-pulmonary, Cardiovascular, Stroke, Cardiac or heart disease, Respiratory, Lower respiratory infections, Chronic obstructive pulmonary diseases, Tuberculosis, Digestive and genitourinary, Neoplasm excluding lung cancer Hospital admissions: Cardiovascular, Stroke, Ischaemic heart disease, Respiratory, Acute respiratory diseases, Acute lower respiratory infections, Chronic obstructive pulmonary diseases, Asthma Virology: Specimens, Flu A+B and Respiratory syncytial virus isolations Meteorological: Temperature, Relative humidity

17. 70 percentiles cut-off 80 percentiles cut-off 90 percentiles cut-off We first assessed a proxy measure for influenza epidemics according to weekly numbers of respiratory deaths above a cut-off. The validity of the measure against the gold standard according to virology data was high.

18. Way forward We will proceed with the following in the coming 5 months. • Standardization of data structure • Statistical modeling • Definition for influenza epidemics • Documentation of research procedure and outputs • Development of common protocol for the PAPA studies

19. Acknowledgement • Health Effect Institute • Environmental Protection Department • Hospital Authority • Department of Health • Census and Statistics Department