Atherosclerosis of the coronary arteries in five towns.

Two atherosclerotic lesions (fatty streak and fibrous plaque) were seen in coronary arteries as early as in the 10-14 age group. Then their frequency increased with age, more rapidly in the left anterior descending coronary artery than in the left circumflex artery. After the age of 55 years fatty streak was still the sole type of lesion in 0.3% of men and an even higher proportion of women. In contrast to the findings in the aorta, the mean extent of fatty streak in the average coronary artery did not exceed 3-4% in all age groups. Fibrous plaque was found in over 90% of men over 40 and women over 50 years of age. The extent of fibrous plaque was greatest by about the age of 65 years in both sexes and showed little change thereafter. The first complicated and calcified lesions appeared in a small proportion of subjects after the age of 20. The frequency of complicated lesions did not exceed 50%, being much lower than that of calcified lesions. Complicated lesions occupied a very small area (mean extent 0.6% in men and 0.3% in women); the extent of calcified lesions in older age groups reached 9-10% of the intimal surface in both sexes. Coronary stenosis appeared after age 20 years in men and 10 years later in women, and its frequency increased with age. There were considerable inter-town differences in the prevalence and extent of atherosclerotic lesions.