The feasibility of routine mortality and morbidity register data linkage to study the occurrence of acute coronary heart disease events in Finland. The Finnish Cardiovascular Diseases Registers (CVDR) Project.

Validated population-based data on the occurrence of coronary heart disease in Finland have previously been obtained from myocardial infarction (MI) registers. Such registers cannot, however, cover large areas. Therefore, the Finnish Cardiovascular Diseases Registers (CVDR) Project was set up to obtain data for the whole of Finland. The CVDR Project is based on routine mortality and morbidity data linkage. We report here the overall approach used in the project, the results of the feasibility study and the first main results. In Finland, data on all hospitalizations are registered in the nationwide Hospital Discharge Register. Also, data on all deaths are collected in the nationwide Causes of Death Register. The unique personal identification number assigned to all persons residing in Finland was used for data linkage. Data have been validated using the FINMONICA MI registers. Sensitivity analyses showed that the data were robust and consistent between different geographical areas. Coronary heart disease (CHD) mortality as well as the incidence and event rates showed the same very clear geographical pattern, dividing Finland to a southwest area with a lower occurrence and a northeast area with nearly twice higher occurrence. Case fatality did not differ much between the areas and did not follow this Southwest-Northeast division. The differences between northeast and southwest Finland may be related to differences in risk factor levels but also to socioeconomic and genetic differences. The CVDR Project data will be instrumental in further research addressing these issues.