The potential for using the case-control design with only hospital separation records was explored in a study of ectopic pregnancy. The Saskatchewan Hospital Services Commission hospital morbidity database was used. Cases were women hospitalized for ectopic pregnancy in the years 1984 through 1986. Controls were women hospitalized for any other pregnancy condition. In a case-control study using pregnant controls, the odds ratio is an appropriate estimator of relative risk, conditional on conception. Among the potential risk factors (exposures) represented in the data were tubal surgery, prior ectopic pregnancy, pelvic inflammatory disease, and infertility. Of these, the first two are completely ascertained during the time a woman was resident in Saskatchewan. Under representation of exposures should be non-differential, leading to odds ratios which are biased towards the null. Multiple logistic regression analysis yielded estimates of the odds ratios for acute PID, chronic PID or pelvic adhesions, prior ectopic pregnancy, tubal sterilization, and tubal repair. Of particular interest was the association between ectopic pregnancy and tubal surgery performed in the hope of maintaining or restoring normal tubal function. The attributable risk proportion of ectopic pregnancy due to such surgery was 8.1%. This study design can be used to follow trends in surgical causes of ectopic pregnancy in Canada. (Abstract shortened by UMI.)

Case-crossover and time series analyses were used to assess associations between ambient air pollutants and asthma hospitalization among children 6--12 years of age living in Toronto between 1981 and 1993. Exposures averaged over periods varying from one to seven days were used. The results from bi-directional case-crossover and time series analyses were similar. Coarse particulate matter (PM10--2.5) was significantly associated with asthma hospitalization in both males and females. The data showed no significant effects of fine (PM2.5) and thoracic (PM10) particulate matter on asthma hospitalizations. Gaseous pollutants, including carbon dioxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2) were significantly related to asthma hospitalization in males or females or both sexes, but ozone (O3) was not. These studies provide strong evidence for asthma hospitalization in children in relation to relatively low levels of ambient air pollution, and suggest that reducing current ambient levels of air pollution will have important population health benefits.

The effect of highly active antiretroviral therapy (HAART) on plasma HCV RNA level in HIV-HCV co-infected individuals is uncertain. This issue was investigated over 12 months in HIV-HCV co-infected subjects HAART-treated for at least six months and achieving HIV RNA suppression below 500 copies/mL. It was predicted that HCV RNA would initially increase from baseline, decline thereafter, and fall below baseline by 12 months. Frozen plasma specimens were used to measure quantitative HCV RNA levels in 50 HAART-treated co-infected subjects at baseline, 3, 6, and 12 months. A 0.5 logo increase in HCV RNA at 3 months was observed. This was followed by a decline below baseline. As low HCV RNA is a predictor of virologic response to HCV therapy, it may be advantageous to first achieve suppression of plasma HIV RNA level, gain immune reconstitution with HAART, and then initiate HCV antiviral treatment in HIV-HCV co-infected individuals.

Background. Diabetics with renal failure have several treatment options including cadaveric (CKT) or living (LKT) kidney transplantation, simultaneous pancreas-kidney transplantation (SPKT), pancreas transplantation after kidney transplantation (PAKT) or dialysis. The objective was to determine the most effective treatment strategy. Methods. Decision analysis comparing dialysis, CKT, LKT, PAKT and SPKT. Model probabilities were obtained from the medical literature and utilities were obtained using the standard gamble. The outcome measure was quality-adjusted life expectancy (quality-adjusted life years, QALYs). Results. LKT was associated with 10.29 QALYs; PAKT, 10.00 QALYs; SPKT, 9.09 QALYs; CKT, 6.53 QALYs; dialysis, 4.52 QALYs. The results were sensitive to several key variables. Conclusion. LKT is the most effective treatment strategy for diabetics with renal failure. However, PAKT is preferred for patients with severe metabolic complications of diabetes and for those patients who favor the kidney-pancreas health state over kidney transplantation alone.

Background. Recent studies of long-term exposure to ambient air pollution suggest that particulate matter in urban air is a risk factor for mortality. However, these studies are potentially biased because they have not taken into account spatial processes. This thesis examines the effect of exposure to sulfate air pollution when place-specific covariates, scale and spatial autocorrelation are controlled for. Methods. This thesis builds upon the American Cancer Society (ACS) Study by introducing place-specific covariates into the original Cox models. In addition, a new two-stage analysis using both metropolitan and county scale covariates is employed in the analysis of the ACS data. Finally a method of filtering out spatial autocorrelation is applied to the data. Results. For all-cause mortality, the original ACS Study found a RR of 1.15 (95% confidence interval of 1.09, 1.22) from sulfates. This was reduced to 1.06 (0.99, 1.13) by the inclusion of the place-specific covariate population change. Using the two-stage method to allow for clustering within metropolitan areas, the RR from sulfates increased to 1.25 (1.13, 1.37). When regional trends were controlled for, the RR decreased to 1.19 (1.06, 1.34). When this metropolitan data was filtered to remove spatial autocorrelation, the RR decreased again to 1.09 (1.01, 1.19). However, when counties were used instead the RR increased to 1.50 (1.30, 1.73). Conclusions. Taking into account spatial processes affects the observed association between ambient sulfate air pollution and mortality. That the sulfate effect is larger and more robust to the inclusion of place-specific covariates at the county scale provides further evidence that ambient sulfate air pollution is a population health hazard.

Ability to pay for physician services is not a barrier to service in Canada, but travel distance may restrict some people's access, especially in rural areas. This thesis examines the distance to the nearest physician from a representative point within each of Canada's census enumeration areas in 1999, and the nature and extent of changes in these distances since 1993. The study is based on the 1999 postal codes of the 56,775 physicians in the Canadian Medical Association registry. Distance to the nearest physician has changed little since 1993; 87% of the population still live less than 5 km from the nearest physician. Distance to the nearest physician was greater in rural areas and small towns, in less urbanized provinces/territories, at higher latitudes, and in less urbanized low-income areas. Physicians-to-population ratios also decreased by 6% from 1993 to 1999.

Le concept moderne du risque, definit maintenant comme un danger est invoque pour proteger l'individu de la menace du sida. En effet la seule facon de proteger la societe est en invoquant la menace individuelle. Etant percu comme une maladie resultant des choix des acteurs individuels, le sida exige des solutions de la meme nature pour enrayer sa dissemination. Considerer l'epidemie du HIV comme un probleme de comportement a risque semble avoir renforce la culture individualiste de la societe industrielle occidentale. Impregnee des stereotypes moralisateurs, du la definition sociale du sida formulee en Occident evoque la notion de responsabilite individuelle. C'est l'individu qui est coupable d'avoir contracte le HIV. Devenue une realite en soi et maintenant universalisee, cette definition de l'epidemie du HIV s'est vue refletee, non seulement dans la facon dont est vue cette problematique ailleurs, tel que dans le Tiers Monde, mais aussi, dans les solutions proposees. Celles-ci contrastent souvent avec les realities des pays du Tiers Monde. (Abstract shortened by UMI.)

In this ecological study hospital emergency admissions in London, Ontario were examined during the peak spring months of the years 1983-88 to determine if asthma morbidity was associated with tree and grass pollen levels. Pollutants and weather factors were also analyzed because they may have confounded the association between asthma and pollen, or may have had their effect modified by pollen. Daily and weekly asthma admissions were associated significantly with tree pollen (r$\sb{\rm s}$ = 0.12 and 0.25 respectively) and total pollen (tree + grass) counts (r$\sb{\rm s}$ = 0.12 and 0.34 respectively) but not with grass pollen alone. The same associations were found using ANOVA after the pollen was categorized into quartiles. These associations stood-up after controlling for confounders. A negative associations of asthma admissions was also found with temperature and this became stronger when pollen counts were elevated. Although negative associations were found for asthma with NO$\sb3$ and SO$\sb4$, these associations are not plausible and may be due to confounding by temperature. The ecological nature of this study prevented ascertainment of exposure and precluded controlling other potential confounders. (Abstract shortened by UMI.)

This thesis was conducted to establish the background for a plan to document the elimination of indigenous wild polio in Canada. Three independent studies were conducted to address the adequacy of polio detection in Canada: (a) a critical review of the existing surveillance system for poliomyelitis in Canada; (b) a retrospective chart review of acute flaccid paralysis (AFP) cases presenting in the Ottawa-Carleton Regional Municipality during a 5-year period (1986-1991); and (c) a cross-sectional survey in Ottawa-Carleton of physicians' awareness about the presentation of poliomyelitis, and their investigative practices for AFP in general. The overall conclusions from the chart review and the physician survey are that among physicians in the study region (a) the index of suspicion for paralytic poliomyelitis is very low, and (b) overall knowledge about the presentation of polio, appropriate diagnostic tests, and requirements for notification are poor, or else not adequately applied. On the basis of the above findings, the conclusion is that Canada does not currently meet the PAHO requirements for certification of a polio-free status. In addition, there is insufficient evidence from the data obtained for the supposition of wild polio elimination in Canada. Recommendations are presented for improving polio surveillance and for establishing protocols for investigation and control of polio. (Abstract shortened by UMI.)

Healthstyles was a community based health promotion program that ran in Ottawa from 1982 to 1984. This program provided an opportunity to assess the effects of health promotion on health behaviours and use of health care services through a quasi-experimental design. Primary analyses of questionnaire responses have shown a number of positive behavioural outcomes. For the secondary analysis, data on health care use 6 months before, 18 months during and 6 months after the program were obtained from Ontario's universal health insurance plan (OHIP). These data were available for 520 volunteer participants and 932 matched controls. Participants and controls were matched on sex, age (within 5 years), education level (2 categories), stress (3 levels), smoking status and an aggregate risk score. Controlling for baseline differences through analysis of covariance, program participants had higher costs and number of visits for ambulatory care during the first year (p 0.01) and second year (p 0.05) after entry into the program. Within ambulatory care, participants used significantly more diagnostic services than controls during both years of follow-up. Participants were also more likely to use counselling and psychotherapy services in year 1 (RR 1.53, 95% CI 1.28, 1.81) and year 2 (RR 1.57, 95% CI 1.31, 1.89). There were no differences between participants and controls in visits for medical consultations and assessments, preventive services or surgical services. These results suggest that health promotion may lead to increased costs and use of ambulatory services, at least over the short-term. However, these costs may be offset over a longer follow-up period if health promotion successfully reduces the incidence of chronic illness. Since the sample population was relatively young and had positive health behaviours at baseline, compared to the general population, the results may not apply to other, less healthy populations.