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Abstract Reprints
1. Creating a population-based linked health database: a new resource for health services research Richard Chamberlayne, Bo Green, Morris L Barer, Clyde Hertzman,
William J Lawrence, Samuel B Sheps As the availability of both health utilization and outcome information becomes increasingly important to health care researchers and policy makers, the ability to link person-specific health data becomes a critical objective. The integration of population-based administrative health databases has been realized in British Columbia by constructing an historical file of all persons registered with the health care system, and by probabilistically linking various program files to this 'coordinating' file. The linkages have achieved a high rate of success in matching service events to person-specific registration records. This success has allowed research projects to be proposed which would otherwise not have been feasible, and has initiated the development of policies and procedures regarding research access to linked data. These policies and procedures include a framework for addressing the ethical issues surrounding data linkage. With continued attention to confidentiality issues, these linked data present a valuable resource for health services research and planning.
2. The epidemiology of cocaine and opiate abuse in urban Canada Christiane Poulin, Pamela Fralick, Elisabeth M Whynot, Nady
el-Guebaly, Dave Kennedy, Joyce Bernstein, Denis Boivin, Joseph Rinehart This study describes the epidemiology of cocaine and heroin abuse in urban Canada as part of an initial report on a national substance abuse surveillance system, the Canadian Community Epidemiology Network on Drug Use. Data pertaining to prevalence of use, law enforcement, treatment, morbidity and mortality of cocaine and heroin were obtained from the appropriate health and law enforcement institutions in six sentinel cities: Vancouver, Calgary, Winnipeg, Toronto, Montreal and Halifax. Cocaine and heroin appear to be more available in Vancouver than in the remaining cities. In all CCENDU cities, large proportions of persons in treatment programs for substance abuse identified cocaine as their major addiction; however, there is considerable variation in treatment utilization regarding heroin. Vancouver ranks first in terms of the per capita number of cocaine and heroin-related hospital separations and mortality rate. Cocaine abuse appears to be an emerging problem in Calgary, Winnipeg and Halifax, and opiate abuse appears to be an emerging problem in Calgary.
3. Recent findings from the Ontario Student Drug Use Survey Edward M Adlaf, Frank J Ivis Background: Every 2 years, the Addiction Research Foundation of Ontario, a division of the Centre for Addiction and Mental Health, sponsors the Ontario Student Drug Use Survey. The results of the surveys conducted in 1995 and 1997 are presented here and compared with results from the early 1990s. Methods: Questionnaires were completed by 3870 and 3990 Ontario public school students enrolled in grades 7, 9, 11 and 13 in 1995 and 1997 respectively. The outcome measures were prevalence of use of 20 types of drugs and other substances, including alcohol, tobacco and prescription drugs, over the previous 12 months. Results: For several drugs the prevalence of use in the previous 12 months had increased from 1993 to 1995, but from 1995 to 1997 there was a significant increase for only one type (hallucinogens such as mescaline and psilocybin). The inhalation of glue declined, and the use of the other 18 types of drugs remained stable. Interpretation: Recent data suggest that increases in adolescent student drug use reported earlier this decade have not continued. However, the stability in rates of drug use is not a justification for complacency in this important area of public health.
4. Screening for prostate cancer: estimating the magnitude of overdetection Maurice McGregor, James A Hanley, Jean-François Boivin, Richard
George McLean Background: No randomized controlled trial of prostate cancer screening has been reported and none is likely to be completed in the near future. In the absence of direct evidence, the decision to screen must therefore be based on estimates of benefits and risks. The main risk of screening is overdetection - the detection of cancer that, if left untreated, would not cause death. In this study the authors estimate the level of overdetection that might result from annual screening of men aged 50-70. Methods: The annual rate of lethal screen-detectable cancer (detectable cancer that would prove fatal before age 85 if left untreated) was calculated from the observed prostate cancer mortality rate in Quebec; the annual rate of all cases of screen-detectable prostate cancer was calculated from 2 recent screening studies. Results: The annual rate of lethal screen-detectable prostate cancer was estimated to be 1.3 per 1000 men. The annual rate of all cases of screen-detectable prostate cancer was estimated to be 8.0 per 1000 men. The estimated case-fatality rate among men up to 85 years of age was 16% (1.3/8.0) (sensitivity analysis 13% to 22%). Interpretation: Of every 100 men with screen-detected prostate cancer, only 16 on average (13 to 22) could have their lives extended by surgery, since the prostate cancer would not cause death before age 85 in the remaining 84 (78 to 87).
5. Factors associated with seat belt use: an evaluation from the Ontario Health Survey Vic S Sahai, J Roger Pitblado, Gary W Bota, Brian H Rowe This study examines the factors associated with seat belt use for drivers and passengers in Ontario. Using the 1990 Ontario Health Survey, a population-based survey of non-institutionalized Ontario residents, factors associated with seat belt use among drivers and passengers were identified and are reported as unadjusted and adjusted odds ratios (OR; 95% CI). Seat belt non-use in Ontario drivers was most strongly associated with younger age (p < 0.0001), high risk health behaviours (drinking and driving (OR: 2.43), speeding (OR: 2.04), smoking (OR: 1.66), being male (OR: 1.87), living in northern (OR: 1.80) or rural (OR: 1.69) regions, and achieving lower education (OR: 1.46). Seat belt non-use in passengers was associated with younger age (p < 0.0001), smoking (OR: 1.62), being male (OR: 1.68), living in northern (OR: 1.63) or rural (OR: 1.46) regions, and low education (OR: 1.31). Vehicular trauma is a major public health problem and seat belt use has been shown to reduce injuries in the event of a crash. Any strategy to increase seat belt use in Ontario should be targeted to involve both drivers and passengers. Attention should be paid to increasing seat belt usage by younger adults, males, and especially those living in northern and rural regions.
6. Dental amalgam and multiple sclerosis: a case-control study in Montreal, Canada Dieudonné Bangsi, Parviz Ghadirian, Slobodan Ducic, Richard
Morisset, Sébastien Ciccocioppo, Ed McMullen, Daniel Krewski Background: The aetiology of multiple sclerosis (MS) remains poorly understood. Dental amalgams containing mercury have recently been suggested as a possible risk factor for MS. Methods: In a case-control study conducted between 1991 and 1994, we interviewed a total of 143 MS patients and 128 controls, to obtain information on socio-demographic characteristics and the number of dental amalgams and the time since installation based on dentists' records. Results: Neither the number nor the duration of exposure to amalgams supported an increased risk of MS. After adjustment for age, sex, smoking, and education those who had more than 15 fillings had an odds ratio (OR) of 2.57 (95% CI : 0.78-8.54) compared to those who had none; for individuals whose first amalgam was inserted more than 15 years prior to the study, we found an OR of 1.34 (95% CI : 0.38-4.72). Conclusions: Although a suggestive elevated risk was found for those individuals with a large number of dental amalgams, and for a long period of time, the difference between cases and controls was not statistically significant.
7. Nutritional factors in the aetiology of multiple sclerosis: a case-control study in Montreal, Canada Parviz Ghadirian, Meera Jain, Slobodan Ducic, Bryna Shatenstein,
Richard Morisset Background: It has been suggested that nutrition and food patterns, particularly high consumption of animal fat and low intake of fish products, may play a role in the aetiology of multiple sclerosis (MS). Methods: The relation between nutritional factors and MS was studied among 197 incident cases and 202 frequency matched controls in metropolitan Montreal during 1992-1995. Dietary information was collected by employing a 164-item food frequency questionnaire in a face-to-face interview. Results: An inverse association was observed between high body mass index (BMI) and the risk of MS, with an odds ratio (OR) of 0.76 (95% confidence interval [CI] : 0.61-0.95), per 5-unit increase in BMI, both sexes combined. In addition, taller women showed a greater risk for MS; the OR per 10 cm increase in height was 1.58 (95% CI : 1.06-2.35). In continuous variable analysis, using the difference between the lowest and highest quartile of intake as a unit, a positive association was observed with energy and animal fat intake. The OR per 897 kcal increase was 2.03 (95% CI : 1.13-3.67) and 1.99 (95% CI : 1.12-3.54) per 33 g of animal fat intake above the baseline. A significant protective effect was observed with other nutrients, including vegetable protein, dietary fibre, cereal fibre, vitamin C, thiamin, riboflavin, calcium, and potassium. Similar trends were seen for males and females when analysed separately. With respect to specific foods (as opposed to nutrients), a higher intake of fruit juices was inversely associated with risk (OR = 0.82; 95% CI : 0.74-0.92). A protective effect was also observed with cereal/breads intake for all cases combined (OR = 0.62; 95% CI : 0.40-0.97) and for fish among women only; pork/hot dogs (OR = 1.24; 95% CI : 1.02-1.51) and sweets/candy (OR = 1.29; 95% CI : 1.07-1.55) were positively associated with risk. Conclusion: The study generally supports a protective role for components commonly found in plants (fruit/vegetables and grains) and an increased risk with high energy and animal food intake.
8. Physical activity, physical fitness and risk
Paul J Villeneuve, Howard I Morrison, Cora L Craig, Douglas E Schaubel We examined the relation between physical activity, physical fitness, and all-cause mortality in a national population-based study of Canadians. We followed men and women ages 20-69 years who had participated in the Canada Fitness Survey between 1981 and 1988. We assessed risk factors for 6,246 men and 8,196 women using multivariate Poisson regression analysis. At baseline, all subjects were asymptomatic according to self-reported screening questions for cardiovascular disease. Men who expended >0.5 kilocalories per kilogram of body weight per day (KKD) experienced a 20% decline in risk of mortality [rate ratio (RR) = 0.82; 95% confidence interval (CI) = 0.65-1.04] when compared with subjects expending <0.5 KKD. We observed a 30% decline in risk of mortality among women expending >3.0 KKD relative to those expending <0.5 KKD (RR = 0.71; 95% CI = 0.45-1.11). Similar patterns of risk were evident for both men and women when analyses were restricted to participation in nonvigorous activities. Those who perceived themselves to be of less than average fitness were at increased risk of mortality (male RR = 1.64, 95% CI = 1.21-2.22; female RR = 1.66, 95% CI = 1.21-2.26). Subjects with undesirable cardiorespiratory fitness levels were more likely to die, compared with those having recommended fitness levels (RR = 1.52; 95% CI = 0.72-3.18). Fifty-three per cent of men and 35% of women reported participating in a vigorous activity. The relation between daily energy expenditure and risk of mortality in these subjects could not be evaluated, as there were few deaths. Nonetheless, our results among participants reporting no vigorous activities support the hypothesis that there is a reduction in mortality risk associated with even modest participation in activities of low intensity.
9. The impact of excluding non-leisure energy expenditure on the relation between physical activity and mortality in women Iris Weller, Paul Corey The purpose of this study was to examine the relation between physical activity and mortality in a 7-year follow-up of a sample of women more than 30 years of age (N = 6,620) from the Canada Fitness Survey cohort, which was initiated in 1981. Age-adjusted relative risks relating quartiles of average daily energy expenditure (kilocalories per kilogram of body weight per day) to mortality were estimated using logistic regression. Compared with the least active, the risk of all-cause mortality was 0.73 for those in the highest quartile (P for trend = 0.03). The associations were stronger for cardiovascular disease mortality (odds ratio = 0.51; P for trend = 0.01) and fatal myocardial infarction (odds ratio = 0.61; P for trend = 0.04) for those in the highest quartile. These relations were due mainly to the contribution of non-leisure (household chores) energy expenditure, which represented, on average, 82% of women's total activity. The accompanying study on the same cohort by Villeneuve et al reported estimates based on a subset of leisure-time physical activity only, which underestimates the activity of many women [CDIC Abstract Reprint No 8]. The resulting bias illustrates the importance of including non-leisure energy expenditure in the assessment of total activity. These data support the hypothesis that physical activity is inversely associated with risk of death in women.
10. Estimation of test sensitivity and specificity when disease confirmation is limited to positive results Stephen D Walter Estimation of sensitivity and specificity for diagnostic or screening tests usually requires independent confirmation of subjects as diseased or nondiseased using a gold standard. In practice, however, application of the confirmatory procedure is usually limited to individuals with one or more positive test results. For situations in which two initial tests are applied, recent literature has shown that one can use the data from confirmed disease cases to estimate the ratio of test sensitivities and the information from confirmed noncases to estimate the ratio of false-positive rates. In this paper, I show that estimates of sensitivity and specificity can be obtained for each test separately, together with an estimate of the disease prevalence. The only additional information required compared with previous methodology is the total number of individuals tested, a quantity that is usually readily available. The assumption that the test errors are independent is required. Although specific patterns of test errors cannot be identified, the overall assumption can be tested using goodness of fit. I illustrate the methods using data on breast cancer screening. Provision of sensitivity and specificity estimates for each test separately provide considerably greater insight into the data than previous methods.
11. The relationship between parental occupation and bone cancer risk in offspring Lisa Hum, Nancy Kreiger, Murray M Finkelstein Background: Bone cancers in children are serious and highly fatal conditions, yet relatively little is known about their causes or methods of prevention. Methods: The relationship between parental occupation and bone cancer in offspring was explored in a case-control study. Cases were identified from the Ontario Cancer Registry; population-based controls were matched on sex and age. Data were collected from their parents through the use of a mailed self-administered questionnaire. Results: The odds ratio estimates (OR) for bone cancer were elevated for fathers in the social sciences (OR = 2.5, 95% confidence interval [CI] : 0.7-8.4). Risk of Ewing's sarcoma was significantly high among children with fathers in social sciences (OR = 6.2, 95 % CI : 1.6-24.5) and mothers in teaching (OR = 3.1, 95 % CI : 1.1-8.7) or farming (OR = 7.8, 95% CI : 1.9-31.7). Osteosarcoma risk was increased for fathers in farming (OR = 2.1, 95% CI : 0.8-5.7), and mothers in managerial and administrative work (OR = 2.3, 95% CI : 0.6-8.1), and product fabricating, assembling, and repairing (OR = 2.0, 95% CI : 0.6-7.2). Conclusions: Certain methodological problems plague studies of bone cancer in children (e.g. small studies, low statistical power, analysis of multiple occupational categories, difficulty in identifying specific carcinogenic agents). These associations require further investigation, especially as elevated risks have been reported previously for agricultural occupations.
12. Breast cancer screening programmes in 22 countries: current policies, administration and guidelines Sam Shapiro, Elizabeth Ann Coleman, Mireille Broeders, Mary Codd,
Harry de Koning, Jacques Fracheboud, Sue Moss, Eugenio Paci, Sylvie
Stachenko, Rachel Ballard-Barbash, for the International Breast Cancer
Screening Network (IBSN) and the European Network of Pilot Projects
for Breast Cancer Screening Background: Currently there are at least 22 countries worldwide where national, regional or pilot population-based breast cancer screening programmes have been established. A collaborative effort has been undertaken by the International Breast Cancer Screening Network (IBSN), an international voluntary collaborative effort administered from the National Cancer Institute in the US for the purposes of producing international data on the policies, funding and administration, and results of population-based breast cancer screening. Methods: Two surveys conducted by the IBSN in 1990 and 1995 describe the status of population-based breast cancer screening in countries which had or planned to establish breast cancer screening programmes in their countries. The 1990 survey was sent to ten countries in the IBSN and was completed by nine countries. The 1995 survey was sent to and completed by the 13 countries in the organization at that time and an additional nine countries in the European Network. Results: The programmes vary in how they have been organized and have changed from 1990 to 1995. The most notable change is the increase in the number of countries that have established or plan to establish organized breast cancer screening programmes. A second major change is in guidelines for the lower age limit for mammography screening and the use of the clinical breast examination and breast self-examination as additional detection methods. Conclusions: As high quality population-based breast cancer screening programmes are implemented in more countries, they will offer an unprecedented opportunity to assess the level of coverage of the population for initial and repeat screening, evaluation of performance, and, in the longer term, outcome of screening in terms of reduction in the incidence of late-stage disease and in mortality.
13. First analysis of mortality and occupational radiation exposure based on the National Dose Registry of Canada JP Ashmore, D Krewski, JM Zielinski, H Jiang, R Semenciw, PR
Band A cohort mortality study of occupational radiation exposure was conducted using the records of the National Dose Registry of Canada. The cohort consisted of 206,620 individuals monitored for radiation exposure between 1951 and 1983 with mortality follow-up through December 31, 1987. A total of 5,426 deaths were identified by computerized record linkage with the Canadian Mortality Data Base. The standardized mortality ratio for all causes of death was 0.61 for both sexes combined. However, trends of increasing mortality with cumulative exposure to whole body radiation were noted for all causes of death in both males and females. In males, cancer mortality appeared to increase with cumulative exposure to radiation, without any clear relation to specific cancers. Unexplained trends of increasing mortality due to cardiovascular diseases (males and females) and accidents (males only) were also noted. The excess relative risk for both sexes, estimated to be 3.0% per 10 mSv (90% confidence interval 1.1-4.8) for all cancers combined, is within the range of risk estimates previously reported in the literature.
14. Immunohistochemical detection of c-erbB-2 and p53 in benign breast disease and breast cancer risk Thomas E Rohan, Warren Hartwick, Anthony B Miller, Rita A Kandel Background: We studied the associations between c-erbB-2 protein overexpression and p53 protein accumulation in benign breast tissue and the risk of subsequent breast cancer. Methods: We conducted a case-control study nested within the cohort of 4888 women in the National Breast Screening Study (NBSS) who were diagnosed with benign breast disease during active follow-up. Case subjects were the women who subsequently developed breast cancer (ductal carcinoma in situ [DCIS] or invasive carcinoma). Control subjects were matched to each case subject on NBSS study arm, screening center, year of birth, and age at diagnosis of benign breast disease. Histologic sections of benign and cancerous breast tissues were analyzed immunohistochemically. Information on potential confounding factors was obtained by use of a self-administered lifestyle questionnaire. Results: Accumulation of p53 protein was associated with an increased risk of progression to breast cancer (adjusted odds ratio [OR] = 2.55; 95% confidence interval [CI] = 1.01-6.40), whereas c-erbB-2 protein overexpression was not (adjusted OR = 0.65; 95% CI = 0.27-1.53). The findings for c-erbB-2 and p53 did not differ among strata defined by menopausal status, allocation within the NBSS, history of breast disease, and whether the benign breast disease was detected at a scheduled screen or between screens. The results were also similar after exclusion of case subjects whose diagnosis of breast cancer occurred within 1 year of their diagnosis of benign breast disease and after exclusion of subjects with DCIS. Conclusions: p53 protein accumulation, but not c-erbB-2 protein overexpression, appears to be associated with an increased risk of progression to breast cancer in women with benign breast disease.
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Last Updated: 2002-10-22 |  |
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