The pathogenesis and triggering factors of acute myocardial infarction in young men remain unknown. To clarify the pathogenesis of acute myocardial infarction in young Japanese men, we compared the clinical features of patients with acute myocardial infarction in 2 age groups in Japan.There were 37 male patients aged40 years (Young group; mean age 36 +/- 4 years, range 23-39 years) among 2,879 patients with acute myocardial infarction admitted to the coronary care unit of the National Cardiovascular Center, Japan, from 1977 through 1996. The clinical features of this group were compared with those of 110 consecutive male patients with acute myocardial infarction agedor = 65 years (Old group; mean age 72 +/- 6 years, range 65-96 years) admitted in 1993-1994. Demographic features, physical activity levels at or within 2 hours before the onset of acute myocardial infarction, and coronary angiographic findings were analyzed.Compared with the Old group, the Young group had lower incidences of hypertension (p0.01) and diabetes mellitus (p0.01), a higher incidence of smoking (p0.01), higher levels of total cholesterol (p0.05) and body mass index (p0.05), and a lower level of high-density lipopotein (HDL)-cholesterol (p0.01). Also, the Young group had a higher prevalence of 0-1 vessel disease than the Old group (72% vs 35%, p0.01). The physical activity level was significantly higher in the Young group than in the Old group (2.6 +/- 2.2 vs 1.8 +/- 1.1 METs, p0.01). Furthermore, patients with multivessel disease in the Young group had a higher incidence of hypertension, a higher level of total cholesterol and a lower level of HDL-cholesterol (all p0.05), whereas those with 0-1 vessel disease had a higher incidence of heavy smoking (73% vs 50%, p = 0.1) and a tendency to higher physical activity level at the onset (2.7 +/- 2.2 vs 2.4 +/- 2.3, NS).Young male patients with acute myocardial infarction may be characterized by 2 distinctive patterns: one associated with smoking and a higher physical activity level at the onset of acute myocardial infarction with 0-1 vessel disease and the other with hypertension and hypercholesterolemia with multivessel disease.
