Risk factors for atherosclerosis and the development of preatherosclerotic intimal hyperplasia

Intimal hyperplasia or thickening is considered to be the precursor lesion for atherosclerosis in humans; however, the factors governing its formation are unclear. To gain insight into the etiology of preatherosclerotic intimal hyperplasia, we correlated traditional risk factors for atherosclerosis with the intimal hyperplasia in an atherosclerosis-resistant vessel, the internal thoracic artery.

Paired internal thoracic arteries were obtained from 89 autopsies. Multivariate logistic regression and multiple regression models were used to examine the association of preatherosclerotic intimal hyperplasia with traditional risk factors for atherosclerosis: age, gender, hypertension, smoking, body mass index, diabetes, and hypercholesterolemia.

Atherosclerotic lesions consisting of fatty streaks and/or type III intermediate lesions were identified in 19 autopsies. Only age >75 years was found to be significantly correlated with atherosclerotic lesion development (P=.01). Multiple regression model of the intima/media ratio in all 89 cases revealed age >75 years (P<.0001), age 51-75 years (P=.0012), smoking (P=.008), and hypertension (P=.02) to be significantly correlated with intimal thickness. In the 70 cases without atherosclerosis, only age 51-75 years (P=.006) and smoking (P=.028) were found to be significantly associated with preatherosclerotic intimal thickening.

In the atherosclerosis-resistant internal thoracic artery, preatherosclerotic intimal hyperplasia routinely forms during adulthood after the fourth decade and is associated with at least two traditional risk factors for atherosclerosis: age and smoking. These observations indicate that in some settings, intimal hyperplasia may be part of the disease process of atherosclerosis and that its formation may be influenced by traditional risk factors for atherosclerosis.