Objective: To evaluate trends in prognosis after acute myocardial infarction (AMI) between Denmark and Sweden using routinely collected data and different case-fatality measures.
Study design and setting: We compared three case-fatality measures during 1987-1999 using national registries in Denmark and Sweden, and extended these measures with underlying deaths of ischemic heart disease and sudden deaths of unknown cause.
Results: Changed coding practice distorted trends of case fatality rates during the day of the event. In general, Denmark had higher case-fatality rates, but trends in hospital-based rates were very similar, except for men 35-64 years old; Denmark declined more steeply. Short- and long-term prognosis improved considerably: the odds ratios for case fatality during days 1-28 for 1999 vs. 1987 were 0.48 among men in Denmark (women 0.58) and 0.53 among men in Sweden (women 0.55) and the odds ratios for case fatality during days 29-365 for 1999 vs. 1987 were 0.56 among men in Denmark (women 0.65) and 0.66 among men in Sweden (women 0.67).
Conclusion: Short- and long-term prognosis improved considerably during 1987-1999 in Denmark and Sweden. Case fatality during the day of the event is epidemiologically important, but less certain than case-fatality measures defined after the day of the event when comparing countries.