A national record linkage to study acute myocardial infarction incidence and case fatality in Sweden

Background During the last decades substantial temporal changes, as well as population differences, in coronary heart disease mortality have occurred in Sweden. There is little information to what extent these changes and dif ferences also apply to myocardial infarction incidence. The aim of this pap er was to describe the methods used to identify cases in a recently develop ed National Acute Myocardial Infarction Register in Sweden, and to present estimates of incidence and case fatality in Sweden. Material and Methods Incident cases of acute myocardial infarction (AMI) we re identified by record linkage of routinely collected data on hospital dis charges and deaths. Case fatality within 28 days was ascertained by linkage of incident cases to the National Cause of Death Register. Results About 40 000 new cases of AMI per year were recorded in Sweden duri ng 1987-1995. Well-known differences in incidence with regard to age and ge nder were observed, as well as a decline in incidence between 1987 and 1995 . A similar case fatality was seen in men and women aged 30-89 among hospit alized cases. When fatal cases outside hospital were also considered the ca se fatality was somewhat higher in men. Examination of medical records for a national sample of ischaemic heart disease patients suggested a high sens itivity (94%) and a high positive predictive value (86%) for ICD-9 code 410 in hospital discharge data with regard to definite AMI. Conclusions The National Acute Myocardial Infarction Register offers a new possibility to study the incidence of AMI, as well as case fatality, in Swe den.