Purpose: Mortality due to coronary disease has declined, but the incidence of myocardial infarction has changed little. Whether the incidence of myocardial infarction reflects that of overall coronary disease is unknown. This study was designed to determine whether the incidence of coronary disease has declined over time.
Methods: We ascertained incident cases of overt coronary disease (myocardial infarction, sudden death, angiographically diagnosed coronary disease, unstable angina not identified under other rubrics) between 1979 and 1998, using medical records of patients in Olmsted County, Minnesota. Secular trends were analyzed with Poisson regression.
Results: Between 1979 and 1998, there were 5772 incident cases of coronary disease (myocardial infarction: 1991; sudden death: 1056; angiographically diagnosed coronary disease: 2514; unstable angina: 211). The age- and sex-adjusted incidence of myocardial infarction declined 6% during these two decades and 3% in the second decade, whereas the incidence of myocardial infarction and sudden death combined declined 17% in the first two decades and 9% in the second decade. Use of angiography increased and served as a measure of coronary disease incidence in the second decade. During the second decade, trends in the incidence of all coronary diseases paralleled those of myocardial infarction and of myocardial infarction and sudden death combined, declining 9% (P = 0.06). Cases of coronary disease diagnosed angiographically increased during the period studied.
Conclusion: The trends that we observed suggest that myocardial infarction and sudden death constitute suitable indicators of trends in coronary disease. The decline in incident coronary disease cases supports the hypothesis that the decline in mortality is explained in part by primary prevention and secondary prevention partially mediated by earlier detection.