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).

Cancer incidence and mortality across Canada.

OBJECTIVES: This article analyses provincial and territorial patterns in incidence and mortality rates for selected cancer sites. DATA SOURCES: Cancer incidence data were obtained from the National Cancer incidence Reporting System and from the Canadian Cancer Registry. Mortality data are from the Canadian Vital Statistics Data Base. ANALYTICAL TECHNIQUES: Age-standardized incidence and mortality rates were calculated for Canada and each province/territory for men and women for major cancer sites for the 1991-1993 period. MAIN RESULTS: Geographic variations in cancer incidence and mortality rates are strongly influenced by trends in the four leading cancers: lung, colorectal, prostate and breast. Cancer rates tended to be significantly high in Quebec and Nova Scotia and significantly low in the three westernmost provinces. These patterns generally reflect provincial/territorial variations in smoking prevalence, dietary habits, and the extent of cancer control programs, such as screening.

Changing trends in melanoma incidence and mortality.

OBJECTIVES: This article analyzes trends in melanoma incidence and mortality rates. Information on sun exposure supplements these statistics. DATA SOURCES: Melanoma incidence data were obtained from the National Cancer Incidence Reporting System and from the Canadian Cancer Registry. Cancer mortality data were extracted from the Canadian Vital Statistics Data Base. Information on sun exposure is from the 1996 Sun Exposure Survey. ANALYTICAL TECHNIQUES: Incidence and mortality rates were age-standardized to the 1991 Canadian population to account for changes in the age structure of the population over time. The average annual percentage changes in age-specific rates were calculated for selected time periods. MAIN RESULTS: After years of steady increases, melanoma incidence and mortality rates have levelled off as a result of declining rates in younger age groups, and for melanoma of the trunk among men and of the leg among women. Incidence rates for men are now higher than those for women; mortality rates for men are twice as high as for women.

Which workers smoke?

OBJECTIVES: This article examines differences by occupation in daily cigarette smoking prevalence and intensity among full-time workers, and how these differences are associated with smoking restrictions at work. DATA SOURCES: Most of the data are from a Health Canada-sponsored Supplement to the 1994/95 National Population Health Survey (NPHS). The analysis is based on 5,674 respondents aged 15 to 64 who were full-time workers at the time of their interview. Comparable information is presented from the 1978/79 Canada Health Survey and the 1986 Labour Force Survey Smoking Supplement. MAIN RESULTS: In 1994/95, 28% of full-time workers were daily smokers, and about a third of them smoked 25 or more cigarettes a day. Smoking prevalence and intensity were lowest among white-collar workers and highest among blue-collar workers. Since 1978/79, there has been an overall decline in smoking prevalence, and since 1986, a decline in smoking intensity among all workers except those in outdoor blue-collar occupations. About 6 in 10 full-time workers who smoked daily encountered restrictions at work.

Incidence and mortality of neuroblastoma in Canada compared with other childhood cancers.

The incidence and mortality of neuroblastoma was reviewed in the general context of childhood cancer in Canada for the periods 1982-86 and 1987-91. This was done to complement the preliminary work of the Quebec Neuroblastoma Screening Project that is studying the impact of screening North American infants for the preclinical detection of neuroblastoma on population-based mortality. Annual age-standardized incidence rates for all childhood cancer in Canada appear to have declined slightly (nonsignificantly) from 155.1 to 150.8 per million, between 1982-86 and 1987-91; the rates for neuroblastoma were stable between the two five-year periods (11.8 per million in 1982-86 and 11.4 per million in 1987-91). With respect to mortality, the age-standardized rates for childhood cancer in Canada have shown a declining trend between the first and second halves of the decade, from 43.4 to 34.7 per million, while the rates for neuroblastoma have not changed (4.4 and 4.2 per million). The age-specific distributions of incident cancers indicate that neuroblastoma accounts for the greatest proportion of all cancers in children less than one year of age. Similarly, neuroblastoma is the leading cause of cancer deaths in children aged one to four years. Theoretically, infants less than one year of age could benefit most from effective preventive interventions, treatment, and research.

Birth cohort and calendar period trends in breast cancer mortality in the United States and Canada.

BACKGROUND: Previous studies of regional and temporal variation in U.S. breast cancer mortality rates have been confined largely to analyses of rates for white women. PURPOSE: Breast cancer mortality rates from 1969 through 1992 for white women and black women in four regions of the United States and for all women throughout Canada were compared to identify racial, regional, and temporal differences. Differences and trends in the rates were evaluated in view of breast cancer risk factors and relevant medical interventions. METHODS: Age-period-cohort models were fit to the data, and changes in birth cohort trends (suggesting a change in a breast cancer risk factor or protective factor) and calendar period trends (suggesting, in part, the impact of new or improved medical interventions) were examined. RESULTS: Breast cancer mortality rates for white women were significantly higher in the Northeast than in any other region of the United States (two-sided t tests; P<.005); the rates for black women were not. Birth cohort trends for all women were similar until about 1940, with a moderation of mortality risk beginning around 1924. A marked moderation of risk by 4-year birth cohorts was observed for U.S. white women born after 1950, whereas stable or slightly decreasing trends were observed for U.S. black women and Canadian women. For women born from 1924 to around 1938, fertility rates increased for all three groups; after 1950, they declined uniformly. Looking at temporal effects, we found that the slope of the mortality calendar period trend increased in the 1980s compared with the 1970s for all women. In the last calendar period, 1991-1992, a trend of decreasing mortality rates was found for white women in the United States and for Canadian women. IMPLICATIONS: Widespread environmental exposures are unlikely to explain the higher relative breast cancer mortality rates observed for U.S. white women in the Northeast, since the rates for black women in this region were not higher than in other regions. The moderation of breast cancer mortality rates for women born between 1924 and 1938 coincides with increased fertility rates following World War II. Stable or decreasing mortality rates for U.S. women and Canadian women born after 1950 were not expected in view of declining fertility rates, suggesting a change in a breast cancer risk factor or protective factor. The increase in calendar period trend slope in the 1980s likely reflects the coincident rise in breast cancer diagnosis via mammography. The recent decline in calendar period trend for white women in the United States and for Canadian women may be the result of earlier detection and increased use of adjuvant therapy.

Cancer in Circumpolar Inuit. Background information for cancer patterns in Canadian Inuit.

The cancer pattern among Inuit in the Circumpolar area is remarkably different from those of other populations in the world. The current paper summarizes the most important risk factors in Canadian Inuit residing in the Northwest Territories, northern Quebec (Nunavik) and Labrador, particularly during the time period 1969-1988 covered by the study. Factors considered include: the geographic area and physical environment; population and human environment, including fertility and life expectancy; lifestyle and diet, including tobacco and alcohol use; other lifestyle factors, and health conditions; and health services and cultural accessibility. Development of the cancer registry and population databases supporting the analysis of cancer rates is described. The information in the present paper is needed to interpret cancer incidence patterns and differences among the Circumpolar Inuit of Canada, Alaska and Greenland.

Cancer among Circumpolar Inuit 1969-1988. Introduction and methods.

Cancer incidence data for Circumpolar Inuit populations were developed and compiled from Greenland, Canada and Alaska from 1969 to 1988 to provide the largest possible base of data for documenting the unusual patterns of cancer previously reported for these populations. Cancer incidence and population data were transferred to the Danish Cancer Registry. Coded information from various ICD-classifications and codes for the basis of diagnosis were transformed to one format, enabling joint analysis. Standard descriptive analysis was carried out with presentation of number of cases, crude incidence rates (CR), age-standardized rates (world) (ASR), cumulative rates to age 64 years, and indirectly standardized ratios (SIR) to the populations of Connecticut (USA), Canada and Denmark. The resulting database can be used to support collaborative international research among the Inuit populations.

Breast cancer in Circumpolar Inuit 1969-1988.

Breast cancer was studied over a 20-year period in Inuit populations in the Circumpolar region. A total of 193 breast cancers were observed in women. The incidence increased from 28.2 per 100 000 in 1969-1973 to 34.3 per 100 000 in 1984-1988. However, the incidence is low, about half what could be expected based on the rates in Denmark, Canada and Connecticut (USA). The low incidence could be explained by the Inuit diet and other lifestyle factors. These benefits should be preserved, in particular in the young, to maintain a low breast cancer incidence.

Cancer of the respiratory system in Circumpolar Inuit.

Cancer incidence of the nasal cavities in Inuit men are high (ASR=3.0 1984-1988), and higher than seen in Denmark, Connecticut (USA) and Canada. Lung cancer incidence is among the highest in the world, for both men and women, and larynx cancer among the lowest. The smoking pattern among Inuit, possibly combined with co-factors related to environment and diet, are believed to be the relevant causal factors.

Cancers of skin, bone, connective tissues, brain, eye, thyroid and other specified and unspecified sites in Inuit.

Low rates of skin cancer, both melanoma and non-melanoma, were observed in Inuit after 20 years of observation. Tumours of the brain and central nervous system, of the thyroid, bone and connective tissues and other specified sites occurred with rates similar to those in comparison populations in Denmark, Connecticut and Canada. These findings support that neither UV and ionizing radiation from nuclear fall-out, nor pollution of herbicides and pesticides in the Arctic area have yet had any noticeable impact on cancer risk. However, unspecified and secondary neoplasms constitute 7-8% of the total Circumpolar cancer incidence and the pattern of rare cancers must be interpreted with caution. Increased diagnostic efforts with a higher precision in the future are warranted.

Cancer in Circumpolar Inuit 1969-1988. A summary.

The results of an international, collaborative study of cancer in Circumpolar Inuit in Greenland, Canada, Alaska and Russia are summarized. A total of 3 255 incident cancers were diagnosed from 1969 to 1988 among 85 000-110 000 individuals. Indirect standardization (SIR) based on comparison populations in Connecticut (USA), Canada and Denmark showed excess risk of cancer of the lung, nasopharynx, salivary glands, gallbladder and extrahepatic bile ducts in both sexes, of liver and stomach cancer in men, and renal and cervical cancer in women. Low risk was observed for cancer of the bladder, breast, endometrium and prostate, and for non-Hodgkin lymphoma, Hodgkin's disease, leukaemia, multiple myeloma and melanoma. Age-standardized incidence rates (ASRs) of cancer of lung, cervix, nasopharynx and salivary glands among Inuit were among the world's highest as were rates in women of oesophageal and renal cancer. Regional differences in ASRs within the Circumpolar area were observed for cancer of the cervix, lung, colon and rectum, liver, gallbladder and breast. The differences in the Inuit cancer incidence pattern to some extent reflect known variations in lifestyle, diet and other exposures, as well as implementation of cancer control measures. Future research addressing possible individual differences are needed to evaluate environmental and genetic factors in etiology and evaluate intervention studies.

Trends in breast cancer incidence and mortality.

Breast cancer is the leading form of cancer diagnosed in Canadian women (excluding non-melanoma skin cancer), accounting for about 30% of all new cases. After age 30, incidence rates begin to rise, and the highest rates are among women aged 60 and over. Canadian incidence rates have increased slowly and steadily since 1969, rising most rapidly among women aged 50 and over. Canada's rates are among the highest of any country in the world, ranking second only to those in the United States. After decades of little change, breast cancer mortality rates for all ages combined have declined slightly since 1990. While not dramatic, this decline is statistically significant and is consistent with similar decreases in the United Kingdom, the United States, and Australia. Breast cancer survival rates are relatively more favourable than those of other forms of cancer. Survival rates are better for younger women and for women whose cancer was detected at an early stage. This article presents breast cancer data from the Canadian Cancer Registry, the National Cancer Incidence Reporting System, and vital statistics mortality data, all of which are maintained by the Health Statistics Division of Statistics Canada. These data are provided to Statistics Canada by the provincial and territorial cancer and vital statistics registrars.

Trends in mammography utilization, 1981 to 1994.

From 1981 to 1994, the annual number of mammograms performed in Canada increased from less than 200,000 to more than 1.4 million. By 1994, about three in five women aged 40 and over reported having had a mammogram at some time in their lives. Most of the increase that occurred between 1985 and 1991 was because of greater use of mammography for breast screening. In the early 1990s, the annual numbers and rates stabilized as the number of mammograms performed on a fee-for-service basis declined slightly, while those conducted by provincial/territorial breast screening programs rose. Mammography is increasingly targeted to women aged 50-69 for whom screening is considered to be most effective. About 30% of Canadian women aged 50-69 have had a mammograms within the past year, although just one-fifth of these mammograms were obtained through provincial/territorial breast screening programs. Most mammography in Canada is provided through the fee-for-service system, although about 80% of fee-for-service mammograms are done for screening purposes, and the remaining 20% for diagnostic assessment. This article is based on administrative data provided by provincial/territorial departments of health and by breast screening programs, as well as on data from the National Population Health Survey. Some implications of mammography utilization for breast cancer incidence and mortality rates are assessed, but because of the long lead time between detection and death, it may be too early to reach definitive conclusions.

Tuberculosis in Canada: a focal disease requiring distinct control strategies for different risk groups.

Cases of new or reactivated tuberculosis (TB) reported in Canadian residents during 1985-1987 (1984-1988 in the province of Quebec) were analyzed by geographic region relative to the geographic distribution of groups known to be at high risk. The crude incidence rate (per 100,000 population) of TB was calculated by census division (or Région socio-sanitaire in Quebec). Rates of TB by census division ranged from 0 to over 200 per 100,000 population; the average rate for Canada was 8.3 per 100,000. Census divisions with very high rates (over 20 per 100,000) were concentrated in the northern regions, with 80% or more of TB cases occurring among aboriginal persons. Census divisions with moderately high TB rates of 10-19 per 100,000 were located either in northerly regions or in major metropolitan areas; reported TB cases in these areas occurred disproportionately in the aboriginal or immigrant populations. Tuberculosis continues to become more geographically focused and limited to aboriginal Canadians, immigrants and the urban poor. Priority must be given to full implementation of effective prevention and control methods in geographic areas with higher incidence rates. Different methods will be required for different areas depending upon the risk groups present.

Cancer incidence by ethnic group in the Northwest Territories (NWT) 1969-1988.

Clear differences occurred in the cancer patterns among the population sub-groups in the NWT. When compared to those for the total Canadian population, rates for all cancers tended to be higher than expected among Inuit, lower than expected among Status Indians, and at expected levels for the Other NWT population. Among Inuit, traditional patterns still persist. Cancers of the lung, cervix, nasopharynx and salivary gland, and choriocarcinoma, occurred more often, and cancers of the breast, prostate, uterus and colon less often than in the total Canadian population. Among Status Indians, small numbers precluded definitive conclusions. However, several cancer sites occurred less often than expected, including colon, bladder and prostate among males, and uterus in females. While no cancer was significantly elevated in either males or females, SIRs for cervix and lung were above 1.0 for females, and kidney cancer was significantly higher when data for both sexes were combined (SIR = 2.0). For the Other NWT group--comprising about 50% of the population--most types of cancers occurred at about the expected rate, except that lung cancer was significantly elevated in females. Nevertheless, the generally high rates for lung and cervical cancer, which were particularly evident among the Inuit, are clearly targets for prevention programmes. It is hoped the cancer registry data now available for twenty years for the NWT, as well as for the overall Canadian Inuit population, can be used by researchers for studies to further determine the etiology of cancers, especially where distinctive patterns occur in these populations.

1992 Canadian Cancer Statistics.

In Canada, it is estimated that in 1992 115,000 new cases of cancer will be diagnosed. This total excludes 47,200 estimated new cases of non-melanoma skin cancer. The number of new cases is increasing by about 3,000 per year due partly to the aging population, improved registration, earlier detection of cancer and real increases in the incidence of some types of cancer. It is estimated that there will be 58,300 cancer deaths in 1992. By 1992, prostate cancer will have overtaken lung cancer as the leading cancer among men in the four western provinces while lung cancer is expected to exceed breast cancer as the leading cause of cancer deaths among women in some provinces, notably British Columbia. In British Columbia, the relative survival rates for most cancers improved between the periods 1970 to 1974 and 1980 to 1984. However, stomach, lung and pancreatic cancers, which have low survival rates, showed little improvement. This article is based on 1992 estimates of cancer incidence and mortality, cancer trends in Canada and relative cancer survival rates in British Columbia, found in Canadian Cancer Statistics 1992. This publication was prepared at Statistics Canada through a collaborative effort involving the Canadian Cancer Society, Health and Welfare Canada and the provincial/territorial cancer registries.

The development of staging data for use in the microsimulation of lung cancer.

Lung cancer incidence rates by cell type and stage were required for a lung cancer microstimulation submodel developed at Statistics Canada. Lung cancer incidence rates not disaggregated by stage were calculated for different histological cell types using Canada's National Cancer Incidence Reporting System data. In the absence of national lung cancer staging information, staging data from the province of Alberta were collected and rates of occurrence were calculated for different stages of lung cancer at time of diagnosis. Imputation procedures were used to maximize the amount of usable staging data. The Alberta stage rates were combined with the Canadian incidence rates to obtain estimates needed by the microsimulation submodel of the annual probability of an individual of a particular sex and age being diagnosed with lung cancer of each cell type at each stage. This project, although highly specialized, illustrates the need for more extensive and standardized staging data for cancer in Canada.

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.