Myocardial infarction and environment. Use of registers in epidemiology.

In the present thesis methods for utilizing some of the many registers in Sweden for epidemiological purposes were further developed. These purposes include immigrant studies, case-control studies dealing with psychosocial job characteristics, and studies of time trends. A theoretical framework for handling problems of misclassification when using register data was developed. Register data were used to examine several hypotheses concerning the occurrence and etiology of myocardial infarction (MI). The result of these all emphasize the role of environmental factors in the etiology of MI. Further information on the relationship between migration and MI was obtained. Male Finnish immigrants in Sweden tend to adopt the lower risk of native Swedes. This implies that environmental factors are important in explaining the difference in incidence of MI between Finland and Sweden. This also implies that it may be possible to decrease the risk by changing environmental conditions. The relationship between psychosocial work environment and MI risk was studied in a new way by using information on occupation. Occupations characterized by hectic work and at the same time providing little possibility for control or growth were significantly associated with an elevated MI risk. The risk for men aged 40-54 years employed in these strenuous occupations was about twice as high as for those in other occupations. This result remained relatively unaffected when several potential confounding factors were taken into consideration. A study was undertaken to examine trends in the incidence and mortality of MI in Stockholm (1974-80). For men the incidence as well as the mortality was appreciably increased. For women there was an appreciable increase in incidence while the increase in mortality was more uncertain. The observed increases in incidence and mortality are contrary to the trend for most other nations in the Western hemisphere. The reason for the increasing trend in Stockholm is, however, unknown.