Karen Y. Fung

Association of Ambient Air Pollution with Respiratory Hospitalization in a Government-Designated “Area of Concern”: The Case of Windsor, Ontario

This study is part of a larger research program to examine the relationship between ambient air quality and health in Windsor, Ontario, Canada. We assessed the association between air pollution and daily respiratory hospitalization for different age and sex groups from 1995 to 2000. The pollutants included were nitrogen dioxide, sulfur dioxide, carbon monoxide, ozone, particulate matter ≤10 μm in diameter (PM10), coefficient of haze (COH), and total reduced sulfur (TRS). We calculated relative risk (RR) estimates using both time-series and case-crossover methods after controlling for appropriate confounders (temperature, humidity, and change in barometric pressure). The results of both analyses were consistent. We found associations between NO2, SO2, CO, COH, or PM10 and daily hospital admission of respiratory diseases especially among females. For females 0–14 years of age, there was 1-day delayed effect of NO2 (RR = 1.19, case-crossover method), a current-day SO2 (RR = 1.11, time series), and current-day and 1- and 2-day delayed effects for CO by case crossover (RR = 1.15, 1.19, 1.22, respectively). Time-series analysis showed that 1-day delayed effect of PM10 on respiratory admissions of adult males (15–64 years of age), with an RR of 1.18. COH had significant effects on female respiratory hospitalization, especially for 2-day delayed effects on adult females, with RRs of 1.15 and 1.29 using time-series and case-crossover analysis, respectively. There were no significant associations between O3 and TRS with respiratory admissions. These findings provide policy makers with current risks estimates of respiratory hospitalization as a result of poor ambient air quality in a government designated “area of concern.”

Association between air pollution and multiple respiratory hospitalizations among the elderly in Vancouver, Canada.

Recurrent events, such as repeated hospital admissions for the same health outcome, occur frequently in environmental health studies. In this study, we conducted an analysis of data on repeated respiratory hospitalizations among the elderly in Vancouver, Canada, for the period of June 1, 1995, to March 31, 1999, using a new method proposed by () for recurrent events, and compared it with some traditional methods. In particular, we assessed the impact of ambient gaseous (SO2, NO2, CO, and O3) and particulate pollutants (PM10, PM2.5, and PM10–2.5) as well as the coefficient of haze (CoH) on recurrent respiratory hospital admissions. Using the new procedure, significant associations were found between admissions and 3-day, 5-day, and 7-day moving averages of the ambient SO2 concentrations, with the strongest association observed at the 7-day lag (RR = 1.044, 95% CI: 1.018–1.070). We also found PM10–2.5 for 3-day and 5-day lag to be significant, with the strongest association at 5-day lag (RR = 1.020, 95% CI: 1.001–1.039). No significant associations with admission were found with current day exposure.

Breast Cancer Survival in Ontario and California, 1998–2006: Socioeconomic Inequity Remains Much Greater in the United States

This study re-examined the differential effect of socioeconomic status on the survival of women with breast cancer in Canada and the United States. Ontario and California cancer registries provided 1,913 cases from urban and rural places. Stage-adjusted cohorts (1998-2000) were followed until 2006. Socioeconomic data were taken from population censuses. SES-survival associations were observed in California, but not in Ontario, and Canadian survival advantages in low-income areas were replicated. A better controlled and updated comparison reaffirmed the equity advantage of Canadian health care.

Associations of Physician Supplies With Breast Cancer Stage at Diagnosis and Survival in Ontario, 1988 to 2006

The authors examined whether the supply of primary care physicians had protective effects on breast cancer stage and survival in Ontario and whether supply losses during the 1990s were associated with diminished protection.

Condensation and validation of a 4-item index of the Acne-QoL

Background: The 19-item Acne-QoL is a validated psychometric instrument designed for use in clinical trials. Objective: The purpose of this study was to develop a condensed version of the Acne-QoL as an alternative measure of psychosocial impact for use in routine clinical practice. Methods: Four condensed versions of the Acne-QoL were evaluated by regression analysis in a subset of 434 patients. The version with four items most broadly representative of acne-specific quality of life combined with a high level of correlation to Acne-QoL total score was selected for further validation in two different patient samples. Results: The patient ranked condensation, representing items from each domain of greatest patient-perceived importance and relevance was selected for further analysis (Acne-Q4). The Acne-Q4 explained 98.5% of the variation in total score of Acne-QoL. Validation of the Acne-Q4 in a follow-up group and an independent subset of patients resulted in Pearson correlation coefficients of 0.967 (p<0.001). Construct validity of the Acne-Q4 was confirmed by demonstrating a similar relationship as the Acne-QoL to acne severity. Limitations: There is less breadth and detail of QoL information in the Acne-Q4 than in the Acne-QoL. The analysis relied on a total score for Acne-QoL, which the original developers did not validate. Conclusions: The Acne-Q4 is accurately reflective of the parent instrument and may facilitate the psychometric evaluation of the impact of facial acne on patients in routine clinical practice by its practicality.

Establishing the spatial variability of ambient nitrogen dioxide in Windsor, Ontario

This study is aimed at identifying the determinants of intra‐urban variation in ambient concentrations of nitrogen dioxide (NO2) in Windsor, Ontario, Canada, and to develop a model to predict NO2 in the city. NO2 samples were collected over a two‐week period during winter 2004 by using passive samplers in 50 locations across Windsor. A land use regression (LUR) model was constructed to generate independent variables that could best predict NO2 concentrations across the city. We tested 71 variables of land use, traffic, road characteristics, population and dwelling counts, and physical geographic variables such as elevation. The final model contained five variables: distance to the Ambassador Bridge, daily traffic on Class 1 and Class 2 arterial roads within 400 m, industry within 600 m, and total population within 700 m. All the variables were statistically significant and had the expected direction of correlation. The final regression model yielded a coefficient of determination, R 2, of 0.88. The spatial variations captured in this analysis are being used to guide the selection of participants for a number of Health Canada studies.

On measurement error adjustment methods in poisson regression

This paper echoes the familiar warning that additive measurement error and multicollinearity in the explanatory variables can mislead investigators in multiple Poisson regression analysis. Often, a causal variable measured with error may be overlooked and its significance transferred to another covariate. Two measurement error adjustment methods were applied and compared in terms of mean squared error of the regression estimates as well as confidence interval coverage of the parameters. Computer simulation was used to evaluate these methods when the explanatory variables are subject to both classical and Berkson error. Results showed that the regression calibration method (RCAL) performed the best in all situations considered, except in the presence of Berkson error when the predictor variables are highly correlated. Copyright

Breast cancer care in the Canada and the United States: Ecological comparisons of extremely impoverished and affluent urban neighborhoods

This study examined the differential effect of extreme impoverishment on breast cancer care in urban Canada and the United States. Ontario and California registry-based samples diagnosed between 1998 and 2000 were followed until 2006. Extremely poor and affluent neighborhoods were compared. Poverty was associated with non-localized disease, surgical and radiation therapy (RT) waits, non-receipt of breast conserving surgery, RT and hormonal therapy, and shorter survival in California, but not in Ontario. Extremely poor Ontario women were consistently advantaged on care indices over their California counterparts. More inclusive health insurance coverage in Canada seems the most plausible explanation for such Canadian breast cancer care advantages.

Physician Supply and Breast Cancer Survival

Background: This study tested the hypothesis that physician supply thresholds are associated with breast cancer survival in Ontario. Methods: The 5-year survival of 17,820 female breast cancer patients diagnosed between 1995 and 1997 was surveilled until 2003 for all-cause mortality. Physician supply densities in 1991 and 2001 were computed for 49 Ontario regions. Results: There were independent threshold effects for general practitioners (GP; 7.25 per 10,000) and obstetrician/gynecologists (OB/GYN; 6 per 100,000) at or above which women with breast cancer were more likely to survive for 5 years. The respective risk of living in areas undersupplied with OB/GYN and GP increased 30% to nearly 5-fold during the 1990s. Five-year survival tended to be lower in provincial areas outside of Toronto, which experienced GP (odds ratio, 0.83; 90% CI, 0.70–0.99) and OB/GYN (odds ratio, 0.76; 95% CI, 0.61–0.96) supply decreases. Conclusion: As they do in America, primary care physician supplies in Canada seem to matter in the effective provision of cancer care. Community resources such as health care service endowments, including physician supplies, may be particularly critical to the performance of health care systems such as Canadas, which aim to provide medically necessary care for all.

Air pollution and daily hospitalization rates for cardiovascular and respiratory diseases in London, Ontario

In this paper, we examine the role that ambient air pollution plays in exacerbating cardiovascular and respiratory disease hospitalization in London, Ontario from 1 November 1995 to 31 December 2000. The number of daily cardiac and respiratory admissions was linked to concentrations of air pollutants (sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide, coefficient of haze, PM10) and weather variables (maximum and minimum of temperature and humidity). Results showed that current day carbon monoxide and coefficient of haze produced significant percentage increase in daily cardiac admissions of 8.0% (95% CI: 1.5–11.5%) and 5.7% (95% CI: 0.9–10.8%) for people < 65 years old. PM10 was found to be significantly associated with asthma admission in the > 65 group, with percentage increase in cardiac admission of 25% (95% CI: 2.8–52.3%) and 26.0% (95% CI: 5.3–50.9%) for current day and 2‐day means, respectively.