Temporal variation in case fatality of acute myocardial infarction in Finland

Background. Previous studies have suggested that seasonal variation and weather conditions have an influence on the incidence and mortality of acute myocardial infarction (AMI). The influence of these factors on AMI case fatality is less studied. Aims. The aim of this study was to examine the temporal variation of AMI case fatality and the effect of daily weather conditions on it. Methods. We analysed death registry and hospital discharge data from all men and women (n=7328) with their first AMI occurrence in the seven largest cities in Finland in the years 1983, 1988, and 1993, aged 25 to 74 years. Results. The mean annual 28-day case fatality was 44%. We found significant weekly and monthly variation of case fatality (P0.001). The December holiday season had the highest case fatality throughout the year in women and men aged 65-74 years (P0.05). The highest weekly case fatality was on Sundays; it differed significantly from the rest of the weekdays only for the oldest age-group (64-74) (P0.01). Conclusions. There is significant weekly and monthly variation in case fatality of AMI. The highest case fatality risk for AMI is during the Christmas season and on Sundays. Weather conditions were not found to have an effect on the case fatality.