Incidence and case fatality rates of acute myocardial infarction (1975-1984): The Worcester Heart Attack Study

During the calendar years 1975, 1978, 1981, and 1984, a community-wide study in the Worcester, Massachusetts, metropolitan area has examined time trends in the attack and case fatality rates of acute myocardial infarction (MI) as well as the occurrence of out-of-hospital coronary heart disease deaths. Between 1975 and 1981, there was a slight increase in the age-adjusted attack rates of acute MI; between 1981 and 1984, however, there was a dramatic decline in the incidence rates of acute MI. These temporal trends over the 10-year period examined resulted in an overall decrease in both the incidence rates of initial (255 per 100,000-1975; 186 per 100,000-1984) as well as recurrent (133 per 100,000-1975; 104 per 100,000-1984) acute MI in the 16 hospitals surveyed. The age-adjusted in-hospital case fatality rates of acute MI declined consistently over the periods studied, from 22.2% in 1975 to 20.3% in 1978, 17.8% in 1981, and to 15.1% in 1984, for an overall decline of 32% over the 10-year period studied. No significant differences, however, were seen in the long-term survival rates of patients discharged from the hospital after acute MI in either 1975, 1978, 1981, or 1984. A consistent decline was seen in the age-adjusted mortality rates (per 100,000) of out-of-hospital coronary heart disease between 1975 (265), 1978 (174), 1981 (170), and 1984 (148). The results of this community-wide study suggest that there has been a recent decline in the attack rates of acute MI and consistent declines over the 10-year period studied in the in-hospital case fatality rates of acute MI end out-of-hospital deaths due to coronary heart disease. These results suggest that recently observed declining coronary heart disease mortality rates seen in the United States may reflect decreases in both the incidence rates of acute MI and out-of-hospital deaths due to coronary heart disease, as well as improvements in the short-term prognosis of patients hospitalized with acute MI.