Status Report--Retracing the history of the early development of national chronic disease surveillance in Canada and the major role of the Laboratory Centre for Disease Control (LCDC) from 1972 to 2000.

TITRE: Rapport d'étape - Historique des débuts de la surveillance nationale des maladies chroniques au Canada et rôle majeur du Laboratoire de lutte contre la maladie (LLCM) de 1972 à 2000. INTRODUCTION: La surveillance de la santé consiste en l'utilisation systématique et continue de données sur la santé recueillies régulièrement en vue d'orienter les mesures de santé publique en temps opportun. Ce document décrit la création et l'essor des systèmes nationaux de surveillance au Canada et les répercussions de ces systèmes sur la prévention des maladies chroniques et des blessures. En 2008, les auteurs ont commencé à retracer l'historique des débuts de la surveillance nationale des maladies chroniques au Canada, en commençant à 1960, et ils ont poursuivi leur examen jusqu'en 2000. Une publication de 1967 a retracé l'historique de la création du Laboratoire d'hygiène de 1921 à 1967. Notre étude fait suite à cette publication et décrit l'historique de l'établissement de la surveillance nationale des maladies chroniques au Canada, à la fois avant et après la création du Laboratoire de lutte contre la maladie (LCDC).

Safe drinking water: a public health challenge.

Disinfection of drinking water through processes including filtration and chlorination was one of the major achievements of public health, beginning in the late 1800s and the early 1900s. Chloroform and other chlorination disinfection by-products (CBPs) in drinking water were first reported in 1974. Chloroform and several other CBPs are known to cause cancer in experimental animals, and there is growing epidemiologic evidence of a causal role for CBPs in human cancer, particularly for bladder cancer. It has been estimated that 14 16% of bladder cancers in Ontario may be attributable to drinking water containing relatively high levels of CBPs; the US Environmental Protection Agency has estimated the attributable risk to be 2 17%. These estimates are based on the assumption that the associations observed between bladder cancer and CBP exposure reflect a cause-effect relation. An expert working group (see Workshop Report in this issue) concluded that it was possible (60% of the group) to probable (40% of the group) that CBPs pose a significant cancer risk, particularly of bladder cancer. The group concluded that the risk of bladder and possibly other types of cancer is a moderately important public health problem. There is an urgent need to resolve this and to consider actions based on the body of evidence which, at a minimum, suggests that lowering of CBP levels would prevent a significant fraction of bladder cancers. In fact, given the widespread and prolonged exposure to CBPs and the epidemiologic evidence of associations with several cancer sites, future research may establish CBPs as the most important environmental carcinogens in terms of the number of attributable cancers per year.

Serum folate and risk of fatal coronary heart disease.

OBJECTIVE: To assess the relationship between serum folate level and the risk of fatal coronary heart disease (CHD) among men and women. DESIGN: Retrospective cohort study with serum folate levels measured from September 1970 to December 1972, with follow-up through 1985. SETTING: Participants in the Nutrition Canada Survey. PARTICIPANTS: A total of 5056 Canadian men and women aged 35 to 79 years with no history of self-reported CHD. MAIN OUTCOME MEASURE: Fifteen-year CHD mortality. RESULTS: A total of 165 CHD deaths were observed. We found a statistically significant association between serum folate level and risk of fatal CHD, with rate ratios for individuals in the lowest serum folate level category (<6.8 nmol/L [3 ng/mL]) compared with the highest category (>13.6 nmol/L [6 ng/mL]) of 1.69 (95% confidence interval, 1.10-2.61). CONCLUSIONS: These data indicate that low serum folate levels are associated with an increased risk of fatal CHD.

Sudden death from asthma in 108 children and young adults.

To identify factors that may contribute to asthma mortality, 108 acute asthma deaths were reviewed. Information was obtained from medical records, next-of-kin, and autopsy records. The fatal asthmatic was characterized by early-onset asthma, severe disease requiring systemic corticosteroids, and prior hospitalization. Risk factors associated with gender, season, employment, and region were also identified. The fatal attack was characterized by an identifiable trigger, delay in seeking medical attention, and rapid deterioration in clinical status. Death due to asthma was confirmed in 95% of autopsied cases. Adrenal cortical abnormalities were recorded for 18.7% of cases. We conclude that, in addition to established risk factors, complications associated with the use of systemic steroids may contribute to the risk for sudden death in this age group.

Canada's health status: a public health perspective.

Health status assessment and disease surveillance are essential to identify and priorize health issues, to evaluate intervention programs and to plan to meet future needs for health services. Canadians currently benefit by having among the highest life expectancies at birth in the world (81 for females, 74 for males). Disability-free life expectancies for females and males, respectively, were 10.1 and 11.3 years lower for the lowest income quintile compared to the highest. Canada's infant mortality rate in 1990 (7/1000 live births) was one of the lowest in the world but within Canada, the rate in the lowest income quintile (10.5/1000 live births) was almost double that in the highest income quintile (5.8/1000 live births). Fair or poor health was reported by 36% of adult Canadians in the lowest income category in 1990 compared to only 5% in the highest income group. The leading causes of premature death for females in 1991 were breast cancer, coronary heart disease, lung cancer, car crashes, birth defects and suicide; those for males were coronary heart disease, suicide, car crashes, lung cancer, birth defects, and AIDS. Lowest income quintile males had mortality rates at least double those for the highest income quintile for alcohol-related conditions, violence, injuries and emphysema. Cardiovascular diseases, cancer, musculoskeletal diseases, injuries and respiratory diseases imposed the highest direct and indirect economic costs in Canada in 1986. For all of these conditions, improved prevention is possible. For example, the forecasted tobacco-related deaths before age 70 among current male smokers age 15 will far exceed those due to car crashes, suicide, murder, AIDS, and drug abuse combined. Population aging will aggravate trends for many chronic conditions especially those with increasing incidence rates; there will be large increases in the numbers of persons with aging-related cancers, dementias and other conditions. There is an urgent need for Canadian health jurisdictions to ensure that rational priorities, goals/objectives, strategies, and programs are in place to enhance prevention and disease control.

Serum iron and risk of fatal acute myocardial infarction.

We assessed the relation of serum iron, dietary iron, and the use of iron supplements to the risk of fatal acute myocardial infarction in the Nutrition Canada Survey cohort. We found an association between serum iron and risk of fatal acute myocardial infarction, with rate ratios for males and females in the highest category of serum iron (> or = 175 micrograms per dl) of 2.18 [95% confidence intervals (CI) = 1.01-4.74] and 5.53 (95% CI = 1.69-18.12), respectively. We found no important association between risk of fatal acute myocardial infarction and either dietary iron or iron supplement use among the 9,920 participants included in this study.

Non-Hodgkin's lymphoma and agricultural practices in the prairie provinces of Canada.

OBJECTIVES: The aim of this study was to provide an update of a cohort study (1971-1985) that previously reported a significant trend in the risk of non-Hodgkin's lymphoma among male Saskatchewan farm operators according to fuel-oil expenditures and herbicide spraying for farms less than 1000 acres (2570 hectares) by including two additional Canadian prairie provinces, two additional years of follow-up, and data from the 1981 Census of Agriculture. METHODS: Information on farmers from 1971 records of the Census of Agriculture was linked to 1971 records of the Census of Population, to 1981 records of the Census of Agriculture, and to death records. Poisson regression was used to estimate risks according to herbicide spraying and fuel and oil expenditures. RESULTS: The addition of a further two years of follow-up resulted in lower risk estimates associated with herbicide spraying for Saskatchewan. No excess risk was observed between herbicide spraying and non-Hodgkin's lymphoma for Alberta or Manitoba in the 1971 data. However, a significantly increased risk of non-Hodgkin's lymphoma according to acres sprayed with herbicides was observed for the three provinces combined when the herbicide spraying data from the 1981 Census of Agriculture was used [> or = 380 acres (> or = 939 hectares) sprayed, rate ratio 2.11, 95% confidence interval 1.1-3.9]. CONCLUSIONS: Although the current results are not entirely consistent with the original Saskatchewan analysis, they support the overall finding of an association between herbicides and risk of fatal non-Hodgkins lymphoma. Prospective cohort studies are needed to overcome the limitations of existing epidemiologic studies.

Risk assessment of physical activity and physical fitness in the Canada Health Survey mortality follow-up study.

The effect of physical fitness and physical activity on all-cause mortality and mortality due to cardiovascular disease (CVD), cancer and other causes was examined using a population-based representative sample of the Canadian population. A total of 691 deaths occurred among persons age 30-69 during the 7-year follow-up period. Of these, 37, 33 and 30% died of CVD, cancer and other causes, respectively. The effect of each risk factor on mortality was assessed using logistic regression analysis. Adjustment was made for age, sex, smoking and body mass index in the case of mortality due to CVD, all causes and causes other than CVD and cancer. Models for mortality due to cancer included adjustment for age, sex, smoking and alcohol consumption. For all cause mortality, those individuals who did not pass the physical fitness tests had significantly higher risks of death than those that passed. For CVD mortality, subjects whose physical activity was moderate were protected, and those who did not pass the physical fitness tests had substantially higher risks of death due to CVD. The risk of death due to cancer was not significantly related to physical activity or physical fitness. Persons who failed the physical fitness tests had significantly elevated risks of death due to causes other than CVD or cancer. Our findings support the conclusion that persons who are physically fit have an overall reduced risk of death independent of other major risk factors. Moderate levels of physical activity appear to be protective against cardiovascular disease.

Increasing brain cancer rates in Canada.

OBJECTIVE: To analyse brain cancer patterns in Canada, particularly according to age and sex distributions, temporal patterns and regional variations. Changes in diagnostic techniques, survival rates and trends by tumour type were also examined. DESIGN: Descriptive epidemiologic study based on Canada-wide population data for 1959-88. OUTCOME MEASURES: Rates of death, incidence and admission to hospital because of brain cancer, as well as survival time and methods of diagnosis. SUBJECTS: Incidence and death rates and time trends were examined for Canada as a whole, by province and by census division. RESULTS: The rates of death from brain cancer increased rapidly among Canadians aged 55 years or more from 1959 to 1988. In particular, age-adjusted death rates increased by 117%, 797% and 118% among men 65 to 74 years, 75 to 84 and 85 or more respectively. The corresponding increases among women were 138%, 535% and 400%. The incidence rates also increased substantially. The trends in incidence rates by tumour type indicated that the increase was more pronounced for glioblastomas. The incidence rates of cases detected histologically, radiologically and clinically all increased. CONCLUSIONS: Because glioblastomas are generally easier to diagnose than astrocytomas and because the incidence rates of glioblastomas were found to increase substantially, the increased brain cancer rates among elderly people may not be entirely attributable to improved diagnostic techniques. However, analytic investigations of the impact of changes in diagnostic procedures on brain cancer trends are needed to clarify this issue.

The relationship of suicide rates to sociodemographic factors in Canadian census divisions.

The correlates of suicide rates were determined by conducting a multivariate study of sociodemographic indicators and suicide rates of 261 Canadian census divisions. Twenty-one sociodemographic variables were entered into a stepwise multiple linear regression to develop a model for suicide rates. The important variables were mortality rate for all causes of death, the age of the population, average family income, population density, proportion with no religious affiliation, proportion of Francophones, unemployment, immigration, proportion of Native people, a regional effect for British Columbia and the north, and growth by mobility, explaining 62% of the observed variation. This spatial ecologic analysis highlights the importance of cultural differences in explaining the variation of suicide rates. The analysis supports the previously found negative relationship between income and suicide while contrasting from previous studies in determining a inverse relationship with unemployment and an inverse relationship with the age distribution.

Long-term survival rates among patients with cancer in Saskatchewan, 1967-1986.

We calculated relative survival rates from 5 to 15 years after diagnosis for cancer cases diagnosed in Saskatchewan, Canada, between 1967 and 1986. Cancers with high 15-year relative survival (greater than 60%) included lip, melanoma among women, other male genital sites, and corpus uteri. As anticipated, relative survival rates declined with increasing length of follow-up, with the largest relative declines noted among those in the oldest age group (65+ years). Only small declines in relative survival were noted for cancers of the colon and cervix with increasing length of follow-up. Improved survival of cases diagnosed in the period 1980-1984 compared to 1970-1974 was observed for all sites combined, as well as the following sites: colon, lung, prostate, brain, ill-defined sites, non-Hodgkin's lymphoma, and lymphoid leukemia. For colorectal cancer, stage at diagnosis was a more important independent predictor of survival than age.

Mortality study of Canadian male farm operators: cancer mortality and agricultural practices in Saskatchewan.

The present investigation involved an analysis of approximately 70,000 male Saskatchewan farm operators, a subset of the 365,000 Canadian farm operators to be investigated in the Canadian Farm Operator Mortality Study. The results of the Saskatchewan analysis indicate that during the interval studied, overall mortality among Saskatchewan farmers was 25% lower than that for all Saskatchewan men, and that, during the same time interval, the risk of death from all types of cancer was also about 25% lower among Saskatchewan farmers than to all Saskatchewan men. Although the present study indicates that overall mortality of death from cancer was 25% lower among Saskatchewan male farmers, there was a relationship between non-Hodgkin's lymphoma mortality and acres sprayed for weeds; a similar risk relationship between expenditures on fuel oil and risk of death from non-Hodgkin's lymphoma was also evident. The magnitude of risk for Saskatchewan farmers is probably greater than that reflected in the estimates in this study, due to the likelihood of misclassification of exposure. There is a particular need for further studies in this area to improve the quantification of farming-related exposures, and to study the exposure history of individuals who develop non-Hodgkin's lymphoma.

Effects of residential exposure to environmental tobacco smoke on Canadian children.

The effects of residential exposure to environmental tobacco smoke were studied in a sample of 6,529 Canadian children under 15 years of age. Univariate analysis indicated an elevated risk of bronchitis among children whose mothers were single, or under age 25, or whose income or educational level was low. Multivariate analysis indicated that the relative risk of bronchitis among children whose mothers were current smokers relative to those whose mothers never smoked was 3.0 (95% CI:1.6,5.2). Significant dose-response relationships between risk of bronchitis and amount smoked as well as duration of exposure were observed. Using the composite exposure score of all smokers in the household as the source of exposure, the risk of bronchitis decreased slightly but remained significantly elevated. Examination of the risk conferred by the mother's smoking relative to the total household exposure showed that most of the elevation in risk was associated with the mother's smoking contribution. Asthma was also studied, but failed to show a statistically significant association with smoking.

Premature deaths in Canada: impact, trends and opportunities for prevention.

The impact, time trends and potential for prevention of premature deaths in Canada were assessed. There were almost 100,000 deaths before age 75 in Canada during 1986 resulting in over 1.7 million potential years of life lost (PYLL). The three leading broad disease categories responsible for PYLL were cancer, injuries/violence and cardiovascular disease. In both sexes, coronary heart disease, car accidents, lung cancer and perinatal conditions ranked in the top 5 specific diseases responsible for PYLL; breast cancer (females) and suicide (males) also ranked in the top 5 conditions. Over the period 1969 to 1986, death rates among persons less than age 75 increased for 3 conditions among females and 11 conditions among males. Lung cancer and brain cancer death rates increased in both sexes, chronic obstructive pulmonary disease death rates increased among females only and death rates for suicide and 8 types of cancer increased among males only. Over the same period, death rates declined for 37 discrete disease categories among both females and males including particularly large improvements for coronary heart disease, stroke, car accidents and perinatal conditions. An estimated 50,000 or over 50% of all premature deaths per year are preventable through control of smoking, hypertension, elevated serum cholesterol, diabetes and alcohol abuse. About 6,000 premature deaths are avoidable through improvements in medical care.

Suicide in Canada: an epidemiological assessment.

Suicide rates in Canada rapidly increased during the 1960s and 1970s. More recent analysis of these trends indicates that in males suicide rates have stabilized and in females a notable decrease has been identified. The greatest changes in suicide rates have occurred among the youngest age groups (15 to 19), while little change has occurred in suicide mortality rates for males aged 50 years and over. The age-specific death rates in 1986 are uniformly distributed in males above age 20, while in females an inverted "U" curve is demonstrated with the peak at age 45-50. Males continue to have higher rates and the difference between males and females is expanding. A birth cohort analysis indicates that the contribution of the birth cohort to explaining suicide rates has diminished and been replaced by a more recent period effect. Suicide remains the second most important cause of death of persons between 15 and 34 years of age. Provincial variation is discussed through geographic variation, cause-specific rankings and potential years of life lost. In contrast to national trends, suicide mortality in Alberta, Quebec and New Brunswick continues to increase. An atlas is provided to display Canadian census divisions that exhibit elevated rates of suicide.

Seasonality in epidemics of asthma mortality and hospital admission rates, Ontario, 1979-86.

Monthly trends in mortality and hospital admission rates attributed to asthma for those aged 15 to 34 for the province of Ontario were examined for the period 1979 to 1986. Graphs showing the monthly variation after the elimination of trend are presented. Time series models were constructed to evaluate the statistical significance. Asthma hospital separations peaked in the autumn and a test for seasonality was statistically significant (p less than 0.001). Although the pattern for asthma mortality was similar, the test for seasonality was not significant (p greater than 0.10).

Mortality study of Canadian male farm operators: non-Hodgkin's lymphoma mortality and agricultural practices in Saskatchewan.

A cohort study of the mortality experience (1971-1985) of male Saskatchewan farmers has been conducted. This study involved linkage of records of the almost 70,000 male farmers identified on the 1971 Census of Agriculture and the corresponding Census of Population to mortality records. Pesticide exposure indices for individual farm operators for the year 1970 were derived from the 1971 Census of Agriculture records. Although the cohort as a whole had no excess mortality for any specific causes of death, including non-Hodgkin's lymphoma, significant dose-response relationships were noted between risk of non-Hodgkin's lymphoma and acres sprayed in 1970 with herbicides, as well as with dollars spent on fuel and oil for farm purposes in 1970. Using Poisson regression modeling, we found that relative risks for the highest level of herbicide use (greater than or equal to 250 acres sprayed) and fuel purchased in 1970 (greater than or equal to $900) on farms less than 1,000 acres total area were 2.2 (95% confidence interval = 1.0-4.6) and 2.3 (95% confidence interval = 1.1-4.7), respectively.