Tze Wai Wong

Air pollution and hospital admissions for respiratory and cardiovascular diseases in Hong Kong

OBJECTIVE: To investigate short term effects of concentrations of pollutants in ambient air on hospital admissions for cardiovascular and respiratory diseases in Hong Kong. METHODS: Retrospective ecological study. A Poisson regression was performed of concentrations of daily air pollutant on daily counts of emergency hospital admissions in 12 major hospitals. The effects of time trend, season, and other cyclical factors, temperature, and humidity were accounted for. Autocorrelation and overdispersion were corrected. Daily concentrations of nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), and particulate matter < 10 microns in aerodynamic diameter (PM10) were obtained from seven air monitoring stations in Hong Kong in 1994 and 1995. Relative risks (RR) of respiratory and cardiovascular disease admissions (for an increase of 10 micrograms/m3 in concentration of air pollutant) were calculated. RESULTS: Significant associations were found between hospital admissions for all respiratory diseases, all cardiovascular diseases, chronic obstructive pulmonary diseases, and heart failure and the concentrations of all four pollutants. Admissions for asthma, pneumonia, and influenza were significantly associated with NO2, O3, and PM10. Relative risk (RR) for admissions for respiratory disease for the four pollutants ranged from 1.013 (for SO2) to 1.022 (for O3), and for admissions for cardiovascular disease, from 1.006 (for PM10) to 1.016 (for SO2). Those aged > or = 65 years were at higher risk. Significant positive interactions were detected between NO2, O3, and PM10, and between O3 and winter months. CONCLUSIONS: Adverse health effects are evident at current ambient concentrations of air pollutants. Further reduction in air pollution is necessary to protect the health of the community, especially that of the high risk group.

Associations between daily mortalities from respiratory and cardiovascular diseases and air pollution in Hong Kong, China

Objective: To investigate the association between ambient concentrations of air pollutants and respiratory and cardiovascular mortalities in Hong Kong. Methods: Retrospective ecological study. A Poisson regression of concentrations of daily air pollutants on daily mortalities for respiratory and cardiovascular diseases in Hong Kong from 1995 to the end of 1998 was performed using the air pollution and health: the European approach (APHEA) protocol. The effects of time trend, seasonal variations, temperature, and humidity were adjusted. Autocorrelation and overdispersion were corrected. Daily concentrations of nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), and particulate matter <10 μm in aerodynamic diameter (PM10) were averaged from eight monitoring stations in Hong Kong. Relative risks (RRs) of respiratory and cardiovascular mortalities (per 10 μg/m3 increase in air pollutant concentration) were calculated. Results: Significant associations were found between mortalities for all respiratory diseases and ischaemic heart diseases (IHD) and the concentrations of all pollutants when analysed singly. The RRs for all respiratory mortalities (for a 10 μg/m3 increase in the concentration of a pollutant) ranged from 1.008 (for PM10) to 1.015 (for SO2) and were higher for chronic obstructive pulmonary diseases (COPD) with all pollutants except SO2, ranging from 1.017 (for PM10) to 1.034 (for O3). RRs for IHD ranged from 1.009 (for O3) to 1.028 (for SO2). In a multipollutant model, O3 and SO2 were significantly associated with all respiratory mortalities, whereas NO2 was associated with mortality from IHD. No interactions were detected between any of the pollutants or with the winter season. A dose-response effect was evident for all air pollutants. Harvesting was not found in the short term. Conclusions: Mortality risks were detected at current ambient concentrations of air pollutants. The associations with the particulates and some gaseous pollutants when analysed singly were consistent with many reported in temperate countries. PM10 was not associated with respiratory or cardiovascular mortalities in multipollutant analyses.

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

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 (PM2.5)) 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 PM2.5 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 PM2.5 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.

SARS Transmission among Hospital Workers in Hong Kong

Despite infection control measures, breakthrough transmission of severe acute respiratory syndrome (SARS) occurred for many hospital workers in Hong Kong. We conducted a case-control study of 72 hospital workers with SARS and 144 matched controls. Inconsistent use of goggles, gowns, gloves, and caps was associated with a higher risk for SARS infection (unadjusted odds ratio 2.42 to 20.54, p < 0.05). The likelihood of SARS infection was strongly associated with the amount of personal protection equipment perceived to be inadequate, having <2 hours of infection control training, and not understanding infection control procedures. No significant differences existed between the case and control groups in the proportion of workers who performed high-risk procedures, reported minor protection equipment problems, or had social contact with SARS-infected persons. Perceived inadequacy of personal protection equipment supply, infection control training <2 hours, and inconsistent use of personal protection equipment when in contact with SARS patients were significant independent risk factors for SARS infection.

Cluster of SARS among Medical Students Exposed to Single Patient, Hong Kong

We studied transmission patterns of severe acute respiratory syndrome (SARS) among medical students exposed exclusively to the first SARS patient in the Prince of Wales Hospital in Hong Kong, before his illness was recognized. We conducted a retrospective cohort study of 66 medical students who visited the index patient’s ward, including 16 students with SARS and 50 healthy students. The risk of contracting SARS was sevenfold greater among students who definitely visited the index case’s cubicle than in those who did not (10/27 [41%] versus 1/20 [5%], relative risk [RR] 7.4; 95% confidence interval [CI] 1.0 to 53.3). Illness rates increased directly with proximity of exposure to the index case. However, four of eight students who were in the same cubicle, but were not within 1 m of the index case-patient, contracted SARS. Proximity to the index case-patient was associated with transmission, which is consistent with droplet spread. Transmission through fomites or small aerosols cannot be ruled out.

Effects of air pollution on asthma hospitalization rates in different age groups in Hong Kong

Aims To assess the relationship between levels of ambient air pollutants and hospitalization rates for asthma in Hong Kong (HK).

Prevalence of migraine and other headaches in Hong Kong.

From July 1992 to March 1993, we conducted a community-based prevalence survey of migraine and other types of recurrent headache by a telephone interview of 2,240 households with 7,356 persons aged 15 and above. 311 patients with recurrent headache were successfully interviewed. Of these, 101 were clinically validated. The overall prevalence rates were 1% for migraine, 2% for tension-type headache and 1% for unclassified headache. Adjusted for misclassification and non-response, the estimated prevalence rates for the three categories were 1.5, 3 and 0.4%, respectively. Agreement between clinical method and questionnaire interview was good for migraine, fair for tension-type headache and poor for unclassified headache. For all three types of recurrent headache, there was a female preponderance with a peak in the 25-44 age group. The prevalence of migraine was much lower than in Western communities but higher than that found in mainland China [1-8]. Common predisposing and aggravating factors for all three types of headaches as reported by the patients were mental stress, physical exertion and menstruation among females. Despite the low prevalence, the overall socioeconomic impact to a populous community is considerable.

Effects of Coarse Particulate Matter on Emergency Hospital Admissions for Respiratory Diseases: A Time-Series Analysis in Hong Kong

Background: Many epidemiological studies have linked daily counts of hospital admissions to particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM10) and ≤ 2.5 μm (PM2.5), but relatively few have investigated the relationship of hospital admissions with coarse PM (PMc; 2.5–10 μm aerodynamic diameter). Objectives: We conducted this study to estimate the health effects of PMc on emergency hospital admissions for respiratory diseases in Hong Kong after controlling for PM2.5 and gaseous pollutants. Methods: We conducted a time-series analysis of associations between daily emergency hospital admissions for respiratory diseases in Hong Kong from January 2000 to December 2005 and daily PM2.5 and PMc concentrations. We estimated PMc concentrations by subtracting PM2.5 from PM10 measurements. We used generalized additive models to examine the relationship between PMc (single- and multiday lagged exposures) and hospital admissions adjusted for time trends, weather conditions, influenza outbreaks, PM2.5, and gaseous pollutants (nitrogen dioxide, sulfur dioxide, and ozone). Results: A 10.9-μg/m3 (interquartile range) increase in the 4-day moving average concentration of PMc was associated with a 1.94% (95% confidence interval: 1.24%, 2.64%) increase in emergency hospital admissions for respiratory diseases that was attenuated but still significant after controlling for PM2.5. Adjusting for gaseous pollutants and altering models assumptions had little influence on PMc effect estimates. Conclusion: PMc was associated with emergency hospital admissions for respiratory diseases in Hong Kong independent of PM2.5 and gaseous pollutants. Further research is needed to evaluate health effects of different components of PMc.

The effects of air pollution on mortality in socially deprived urban areas in Hong Kong, China

Background Poverty is a major determinant of population health, but little is known about its role in modifying air pollution effects. Objectives We set out to examine whether people residing in socially deprived communities are at higher mortality risk from ambient air pollution. Methods This study included 209 tertiary planning units (TPUs), the smallest units for town planning in the Special Administrative Region of Hong Kong, China. The socioeconomic status of each TPU was measured by a social deprivation index (SDI) derived from the proportions of the population with a) unemployment, b) monthly household income < US

Why Did Outbreaks of Severe Acute Respiratory Syndrome Occur in Some Hospital Wards but Not in Others

250, c) no schooling at all, d) one-person household, e) never-married status, and f ) subtenancy, from the 2001 Population Census. TPUs were classified into three levels of SDI: low, middle, and high. We performed time-series analysis with Poisson regression to examine the association between changes in daily concentrations of ambient air pollution and daily number of deaths in each SDI group for the period from January 1996 to December 2002. We evaluated the differences in pollution effects between different SDI groups using a case-only approach with logistic regression. Results We found significant associations of nitrogen dioxide, sulfur dioxide, particulate matter with aerodynamic diameter < 10 μm, and ozone with all nonaccidental and cardiovascular mortality in areas of middle or high SDI (p < 0.05). Health outcomes, measured as all nonaccidental, cardiovascular, and respiratory mortality, in people residing in high SDI areas were more strongly associated with SO2 and NO2 compared with those in middle or low SDI areas. Conclusions Neighborhood socioeconomic deprivation increases mortality risks associated with air pollution.