Changes in frequency of cerebrovascular diseases in Oslo, Norway, 1958-1977. An autopsy study.

The frequency of lethal stroke was examined over a 20-year period in a large collection of autopsy material and was compared with the official mortality statistics for the same period. The frequency of lethal stroke in the autopsy material was calculated as a percentage of the total number of autopsied patients in the corresponding age groups. The frequency of strokes found in mortality statistics was calculated as a percentage of all deaths in the corresponding age groups. In the autopsy material the over-all stroke frequency fell by 14 percent. For patients between 40 and 69 years the decline was 25 percent while for patients over 70 years only a minor drop was observed. The most marked decline was 25 percent while for patients over 70 years only a minor drop was observed. The most marked decline was found for intracerebral hemorrhage which decreased by 70 percent in patients between 40 and 69 and by 33 percent for those over 70. For brain infarction the decline was 32 percent in the youngest age group while patients over 70 showed no decrease at all. MOrtality statistics showed a steady decline in the frequency of stroke death and the overall figures in the 2 sources were similar. Figures fo the stroke sub-groups (brain infarction and intracranial hemorrhage) were markedly different from those found in the autopsy records. Frequency of hemorrhage was several times greater than that of infarction in mortality statistics while the reverse was true in the autopsy records. The sources of error are discusses for both materials. It is concluded that the over-all figures for stroke deaths are largely reliable for both autopsy records and mortality statistics. In the mortality statistics the separate figures for hemorrhages and infarction were not correct and long term changes in frequency of these conditions would be interpreted with caution. The figures from the autopsy material are considered to be more reliable and it is concluded that the decline in hemorrhage and infarction described is real.