Are geographical differences in cardiovascular mortality due to morbidity differences or to methodological differences? The project "myocardial infarction in Mid-Sweden".

Geographical variations in cardiovascular mortality have been reported from Mid-Sweden. IHD mortality for men aged 45-64 was 60% higher in the western part than in the east. Mortality from stroke for men aged 45-74 was 73% higher on the west. Similar differences were found for women. One possible explanation could be that there are no incidence differences but that the mortality differences are due to different survival rates or to differences certifying the cause of death. These two possible explanations were tested in this study. Data for all patients hospitalised during the 10-year period 1972-1981 for myocardial infarction or stroke in a high mortality area, the County of Värmland in the west, and a low mortality area, the County of Uppsala in the east, were collected. In addition, a substudy was performed where the basis for the death certificate diagnosis was studied. The western area generally had a higher case fatality rate than the eastern. However, a larger proportion of the deaths the eastern area, occurred outside hospital, so that the net effect would be that the differences found were not large enough to explain the mortality differences. The autopsy rate in the western part was lower than in the east but since a larger proportion of the deaths occurred in hospital the rank order for IHD and stroke mortality between east and west was the same whether all IHD or stroke deaths were counted or only those considered the most well documented.