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1.  Modelling continuous data 
PMCID: PMC1216295  PMID: 16186569
2.  Mortality among subjects with chronic obstructive pulmonary disease or asthma at two respiratory disease clinics in Ontario 
Chronic obstructive pulmonary disease (COPD) accounts for nearly three million deaths annually, with approximately 5% of deaths in Canada attributed to COPD in 2004. Mortality rates among individuals with COPD or asthma, however, are not extensively studied in North America. Certainly, follow-up of individuals with respiratory diseases can shed light on mortality risks and contribute valuable information to prevent premature death. Accordingly, this retrospective study investigated mortality rates and examined risk factors for premature death among patients diagnosed with respiratory diseases identified from two lung function testing databases of two respiratory clinics in Ontario during the 1990s.
Chronic obstructive pulmonary disease (COPD) and asthma are common; however, mortality rates among individuals with these diseases are not well studied in North America.
To investigate mortality rates and risk factors for premature death among subjects with COPD.
Subjects were identified from the lung function testing databases of two academic respiratory disease clinics in Hamilton and Toronto, Ontario. Mortality was ascertained by linkage to the Ontario mortality registry between 1992 and 2002, inclusive. Standardized mortality ratios were computed. Poisson regression of standardized mortality ratios and proportional hazards regression were performed to examine the multivariate effect of risk factors on the standardized mortality ratios and mortality hazards.
Compared with the Ontario population, all-cause mortality was approximately doubled among subjects with COPD, but was lower than expected among subjects with asthma. The risk of mortality in patients with COPD was related to cigarette smoking, to the presence of comorbid conditons of ischemic heart disease and diabetes, and to Global initiative for chronic Obstructive Lung Disease severity scores. Individuals living closer to traffic sources showed an elevated risk of death compared with those who lived further away from traffic sources.
Mortality rates among subjects diagnosed with COPD were substantially elevated. There were several deaths attributed to asthma among subjects in the present study; however, overall, patients with asthma demonstrated lower mortality rates than the general population. Subjects with COPD need to be managed with attention devoted to both their respiratory disorders and related comorbidities.
PMCID: PMC3267622  PMID: 22187688
Asthma; Cohort study; COPD; Mortality; Risk factors
6.  A Cohort Study of Traffic-Related Air Pollution and Mortality in Toronto, Ontario, Canada 
Environmental Health Perspectives  2009;117(5):772-777.
Chronic exposure to traffic-related air pollution (TRAP) may contribute to premature mortality, but few studies to date have addressed this topic.
In this study we assessed the association between TRAP and mortality in Toronto, Ontario, Canada.
We collected nitrogen dioxide samples over two seasons using duplicate two-sided Ogawa passive diffusion samplers at 143 locations across Toronto. We calibrated land use regressions to predict NO2 exposure on a fine scale within Toronto. We used interpolations to predict levels of particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) and ozone levels. We assigned predicted pollution exposures to 2,360 subjects from a respiratory clinic, and abstracted health data on these subjects from medical billings, lung function tests, and diagnoses by pulmonologists. We tracked mortality between 1992 and 2002. We used standard and multilevel Cox proportional hazard models to test associations between air pollution and mortality.
After controlling for age, sex, lung function, obesity, smoking, and neighborhood deprivation, we observed a 17% increase in all-cause mortality and a 40% increase in circulatory mortality from an exposure contrast across the interquartile range of 4 ppb NO2. We observed no significant associations with other pollutants.
Exposure to TRAP was significantly associated with increased all-cause and circulatory mortality in this cohort. A high prevalence of cardiopulmonary disease in the cohort probably limits inference of the findings to populations with a substantial proportion of susceptible individuals.
PMCID: PMC2685840  PMID: 19479020
air pollution; GIS; mortality; nitrogen dioxide; traffic air pollution; Toronto
7.  Effectiveness of selective serotonin reuptake inhibitors 
PMCID: PMC2292765  PMID: 18427097
8.  Relation between income, air pollution and mortality: a cohort study 
Community levels of air pollution have been associated with variability in mortality rates, but previous studies have inferred exposure to pollutants on a citywide basis. We investigated mortality in relation to neighbourhood levels of income and air pollution in an urban area.
We identified 5228 people in the Hamilton–Burlington area of southern Ontario who had been referred for pulmonary function testing between 1985 and 1999. Nonaccidental deaths that occurred in this group between 1992 and 1999 were ascertained from the Ontario Mortality Registry. Mean household income was estimated by linking the subjects' postal codes with the 1996 census. Mean neighbourhood levels of total suspended particulates and sulfur dioxide were estimated by interpolation from data from a network of sampling stations. We used proportional hazards regression models to compute mortality risk in relation to income and pollutant levels, while adjusting for pulmonary function, body mass index and diagnoses of chronic disease. Household incomes and pollutant levels were each divided into 2 risk categories (low and high) at the median.
Mean pollutant levels tended to be higher in lower-income neighbourhoods. Both income and pollutant levels were associated with mortality differences. Compared with people in the most favourable category (higher incomes and lower particulate levels), those with all other income–particulate combinations had a higher risk of death from nonaccidental causes (lower incomes and higher particulate levels: relative risk [RR] 2.62, 95% confidence interval [CI] 1.67–4.13; lower incomes and lower particulate levels: RR 1.82, 95% CI 1.30–2.55; higher incomes and higher particulate levels: RR 1.33, 95% CI 1.12–1.57). Similar results were observed for sulfur dioxide. The relative risk was lower at older ages.
Mortality rates varied by neighbourhood of residence in this cohort of people whose lung function was tested. Two of the broader determinants of health — income and air pollution levels — were important correlates of mortality in this population.
PMCID: PMC183288  PMID: 12952800
9.  Preventive screening. What factors influence testing? 
Canadian Family Physician  2002;48:1494-1501.
OBJECTIVE: To determine factors associated with having preventive screening tests in a population-based sample of Ontario women. DESIGN: Secondary analysis of data from Statistics Canada's National Population Health Survey linked to data from the Ontario Health Insurance Plan to ascertain whether women aged 20 or older had Pap smears, mammography, bone densitometry, or cholesterol testing. Factors associated with having testing were subjected to logistic regression analysis. SETTING: Ontario. PARTICIPANTS: Women aged 20 or older; from 19,600 Canadian households, 2232 Ontario women gave consent to linkage of administrative databases. MAIN OUTCOME MEASURES: Age-specific population screening rates. Odds ratios and probabilities of having screening in relation to socioeconomic, geographic, and physician-associated factors. RESULTS: Having screening was associated with age, income, education, and place of residence. Women with regular physicians were more likely to have Pap smears (odds ratio [OR] 4.4, range 1.7 to 12), densitometry (OR 22, range 3.6 to 140), and cholesterol testing (OR 8.0, range 2.3 to 29). Women who had periodic health examinations were more likely to have Pap smears (OR 6.7, range 4.6 to 9.8), mammograms (OR 3.7, range 2.3 to 5.9), densitometry (OR 3.7, range 1.3 to 10.5), and cholesterol testing (OR 3.0, range 2.0 to 4.5). The probability of having testing increased with number of visits a year to a doctor, but ceased to increase after three visits. CONCLUSION: Having screening tests was associated with socioeconomic factors including income, education, and place of residence. Patients who went to doctors for episodic care only were less likely to have preventive screening than patients who went for periodic health examinations.
PMCID: PMC2214098  PMID: 12371308
10.  Medical conditions, medications, and urinary incontinence. Analysis of a population-based survey. 
Canadian Family Physician  2002;48:96-101.
OBJECTIVE: To assess associations between various medical conditions and drug treatments and reports of urinary incontinence. DESIGN: Secondary analysis of responses to the second wave of the National Population Health Survey (NPHS). Odds ratios were calculated using survey-weighted multiple logistic regression; confidence intervals were calculated using bootstrap methods. SETTING: Canadian households in all 10 provinces, as assessed by Statistics Canada's NPHS. PARTICIPANTS: From among respondents to the NPHS, the 54,920 people aged 30 years or older. MAIN OUTCOME MEASURES: Responses to the question "Do you have urinary incontinence diagnosed by a health professional?" and analysis of variables related to medical conditions and medications. RESULTS: Urinary incontinence was associated with strokes, arthritis, and back problems in both sexes. Odds ratios for incontinence were elevated among men and women who reported having asthma. Narcotics and diuretics were strongly associated with incontinence in both sexes. Psychoactive medications were associated with incontinence in women; antidepressants were associated with incontinence in men. CONCLUSION: Physicians should consider the possibility that patients with common conditions, such as arthritis, back problems, or respiratory conditions associated with coughing, might also have urinary incontinence. Physicians should also be aware that urinary incontinence might be a side effect of therapies and make relevant inquiries. Medications associated with incontinence could be changed.
PMCID: PMC2213925  PMID: 11852617
11.  Do factors other than need determine utilization of physicians' services in Ontario? 
Universal health care systems seek to ensure access to care on the basis of need, rather than income, but there are concerns about preferential access to cardiovascular and specialist care for high income patients. In this study, I used population-based, individual-level health, income and utilization data to determine whether whether there is evidence for differential access to physician care in relation to household income.
I studied data for 2170 Ontario respondents to the 1995 National Population Health Survey (aged 40 to 79 years) who had approved linkage of their survey responses to the administrative databases of the Ontario Health Insurance Plan and for whom income data were available. I used linear and generalized linear regression to model the mean per capita expenditures on physician care and the probability of referral to a specialist in relation to income and self-reported health status.
Residents of higher income households incurred lower per capita expenditures for physicians' services than those in lower income households; for example, the mean per capita expenditure in the upper middle income group was $220 less (95% confidence interval –$87 to –$334) than the mean per capita expenditure in the lowest income group. Expenditures were significantly related to self-reported health status; for example, the mean per capita expenditure among those reporting fair health status was $590 higher (95% confidence interval $465 to $737) than among those reporting excellent health. After adjustment for health status, there was no association between income and the expenditures on all physician services, out-of-hospital services or specialist care.
Utilization of physicians' services in Ontario is based on need, rather than income.
PMCID: PMC81414  PMID: 11563208

Results 1-11 (11)