Epidemiologic study of work-related diseases. Methodological problems of register-based studies.

The efficient execution of an occupational epidemiologic study requires accurate information on both exposure and effect. In this paper emphasis is placed on the use of registers of occupation or disease as tools in the undertaking of descriptive and analytical epidemiologic studies. While cancer registers are a common information source nowadays, their validity is not always consistently good. Other sources of information, such as industry records, professional membership listings, and disease notifications are also used. The inaccuracies of these registers--established usually for nonepidemiologic purposes--are outlined. Specific examples are used to illustrate the problems and pitfalls involved in interpreting the derived results. The study populations discussed range from the high enumeration feasible with life-long occupational groupings, such as pathologists and sea pilots, to attempts to trace individuals whose "membership" in an exposure group might be residence in the American Embassy in Moscow or recognition as short-service military personnel exposed to A-bomb testing a generation ago. The recent development of using census-based occupational information to trace mortality and morbidity is also discussed.