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).

First analysis of cancer incidence and occupational radiation exposure based on the National Dose Registry of Canada.

A cohort study was conducted to investigate the relation between cancer incidence and occupational exposure to ionizing radiation. Records containing dose information from 1951 to 1988 for 191,333 persons were extracted from the National Dose Registry of Canada. The records were linked to the Canadian Cancer Data Base, with incidence data from 1969 to 1988. Standardized incidence ratios were calculated using Canadian cancer incidence rates stratified by age, sex, and calendar year. Excess relative risks were obtained from internally based dose-response analyses. The following significant results were found for males and females combined: a deficit in the standardized incidence ratio for all cancers combined; elevated standardized incidence ratios for thyroid cancer and melanoma; and elevated excess relative risks for rectum, leukemia, lung, all cancers combined, all except lung, and all except leukemia. For males, cancers of the colon, pancreas, and testis also showed significantly elevated excess relative risks. The specific cancer types listed above have been implicated in previous studies on occupational exposure to ionizing radiation, except for testis, colon, and melanoma, while the findings on thyroid cancer from previous studies are inconclusive. The thyroid standardized incidence ratios in this study are highly significant, but further investigation is needed to assess the possibility of association with occupational radiation exposure.

Surveillance of potential associations between occupations and causes of death in Canada, 1965-91.

OBJECTIVE: To detect unsuspected associations between workplace situations and specific causes of death in Canada. METHODS: An occupational surveillance system was established consisting of a cohort of 457,224 men and 242,196 women employed between 1965 and 1971, constituting about 10% of the labour force in Canada at that time. Mortality between 1965 and 1991 has been determined by computerised record linkage with the Canadian mortality database. Through regression analysis, associations between 670 occupations and 70 specific causes of death were measured. RESULTS: There were almost 116,000 deaths among men and over 26,800 deaths among women. About 28,000 comparisons were made between occupations and specific causes of death. With various reporting criteria, several potential associations were highlighted, including: infectious disease mortality among barbers and hairdressers; laryngeal cancer among male metal fitters and assemblers; lung cancer among female waiters; breast cancer among female metal fitters and assemblers; brain cancer among female nursing assistants and male painters; and ischaemic heart disease among female inspectors and foremen and among male taxi drivers and chauffeurs. CONCLUSIONS: When excess risk of mortality is apparent, the intention of this occupational surveillance system is to spark further studies to gain aetiological knowledge.

Application of exact ODDS for partial agreements of names in record linkage.

Automated methods for linking records pertaining to the same individuals have in the past made only crude use of the name information. A perceptive filing clerk is more sophisticated because humans retain a lifetime memory of instances in which variant forms of names were employed interchangeably, and of synonyms that sometimes did not even resemble one another. This limitation of the machine can be rectified, but the body of knowledge required to serve as its memory must be large. The needed data have now been brought together on a suitable scale, from many past searches of Canada's Mortality Data Base. Described here are the development and use of the resulting tables of essentially exact discriminating powers (or ODDS) to do with comparisons of male given names. The aim is to reduce the proportion of ambiguously linked pairs of records requiring labor intensive clerical resolution. The tables are intended for general use in this country, and as a model for similar facilities appropriate to other populations.

Canadian Farm Operator Study: methodology.

A mortality study of about 326,000 Canadian male farm operators enumerated in the 1971 Census of Agriculture is being conducted by Health and Welfare Canada in collaboration with Statistics Canada. The study examines the mortality patterns of farm operators in relation to farm practices and a variety of socio-demographic variables. The prime concern is the association between pesticide use and certain cancers suggested in previous studies of farmers. This article describes the methodology used to create the study cohort and the analysis files. Highlights of the preliminary results from this study for Saskatchewan are also presented. Results for other regions are forthcoming. Among the Saskatchewan cohort of farm operators, 94% of deaths occurred within the province. The average age at death was 67.9 years and the average length of survival from 1971 was 13.9 years. Although the cohort as a whole had no excess mortality for any specific cause of death--including non-Hodgkin's lymphoma--significant dose-response relationships were noted between risk of non-Hodgkin's lymphoma and acres sprayed with herbicides in 1970, as well as with dollars spent in 1970 on fuel and oil for farm purposes (1).

A standard data collection-package for medical follow-up studies.

A standard method of collecting identifying data for medical follow-up studies has been developed by Statistics Canada. By helping improve health record-keeping, this method has the potential to make it easier to track populations exposed to potentially hazardous agents through lifestyle, work, environmental factors, ecological disasters, or medical treatments. The data collection package, which has been reviewed by expert groups and pilot tested, can reduce costs, save time and result in more comparable data. The package guides the user in developing an easily maintained and accessed database using either the Data Collection Package handbook or the personal computer package option. Part I of this article gives an overview of the new data collection package and how it can be used. Part II gives the background and methodological notes on its development.

Discriminating powers of partial agreements of names for linking personal records. Part I: The logical basis.

Machines have difficulty when using people's names to link medical and other records pertaining to the same individuals because of nicknames, ethnic synonyms, truncations, misspellings and typographical errors. Present algorithms used to compute the discriminating powers (or ODDS) associated with partial agreements of names are based, inappropriately, on the degrees of outward similarity alone. They are particularly ineffective in dealing with names that look alike but are unrelated, and with related names that have little apparent similarity. A fundamentally different rationale is, therefore, proposed which, like the human mind, assesses the relatedness of two alternative forms of a name in terms of how often they are used, interchangeably in practice. This must be taken into account if the associated discriminating powers (ODDS) are to be correctly computed. A way of implementing this more precise approach is described and illustrated, using the given names on linked records from an earlier epidemiological study. This first study of two describes the logical basis for record linkage, a second one the empirical test.

Discriminating powers of partial agreements of names for linking personal records. Part II: The empirical test.

The preceeding paper examined the logical basis of an exact way of calculating the discriminating powers of people's names when they only partially agree. The method has application to automated file searching and record linkage. The present account describes an empirical test of the approach. Use is made of some 2000 comparison pairs of male given names, obtained as a byproduct from an earlier linkage study. The test shows that exact value-specific ODDS can indeed be calculated for common names when compared with their accepted synonyms (e.g. JOSEPH versus JOE). Moreover, the use can be extended to include rare variants, by arranging these into groups defined in value-specific terms (e.g. as selected blocks in an alphabetically sequenced listing, or combinations of such blocks). A majority of all name comparisons may be handled in this manner. The added precision serves to reduce the numbers of records that are ambiguously linked and require labour intensive clerical resolution.

Comparison of individual follow-up and computerized record linkage using the Canadian Mortality Data Base.

We compared two methods of ascertaining mortality in a historical prospective mortality study. Computerized Record Linkage (CRL) with the centralized historical Canadian Mortality Data Base (CMDB) was carried out on 2469 men and an attempt was also made to trace the subjects by individual follow-up (IFU). All but 88 were traced and 60 were reported to be dead. CRL was able to locate the deaths of three men who had been untraced by IFU. Contradictory information on vital status was obtained on 5 subjects--in 4 of them, the discrepancy was resolved in favour of CRL. Overall, CRL using the CMDB performed very well. We also consider factors that affect the relative costs of the two methods, which should be balanced against the accuracy of information obtained.