Geographic comparisons of diffuse intimal thickening of the aorta.

Aortic intimal thickness was measured microscopically in samples taken from areas grossly free of atherosclerotic lesions of 2,472 subjects aged 15 through 64 years collected during the first year of the International Atherosclerosis Project (IAP). Results indicate that there is progressive increase in aortic intimal thickness with increasing age in both sexes. No differences were observed between the upper thoracic and abdominal aorta. Mean intimal thickness does not appear to be consistently thicker in males than in females. Some differences were found in mean thickness among the 19 location--race groups included; however, such differences did not parallel those observed among the same location--race groups by the mean level of atherosclerosis. A few subjects with Coronary Heart Disease (CHD) and atherosclerosis-related cases had slightly thicker intimas. Diffuse Intimal Thickening (DIT) detected grossly correlates well with thicker means of intimal thickness in both sexes in the abdominal aorta and the thoracic aorta in females. DIT appears to be a universal phenomenon mainly age-dependent; it also appears to be increased in some (CHD) and atherosclerosis-related conditions.