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Smoking and echogenicity of the arterial intima

Institution: University of Southern California
Investigator(s): James Dwyer, Ph.D.
Award Cycle: 2000 (Cycle 9) Grant #: 9IT-0177 Award: $119,299
Subject Area: Epidemiology
Award Type: Inno Dev & Exp Awards (IDEAS)

Initial Award Abstract
The Los Angeles Atherosclerosis Study (LAAS) is a study of the development of the disease known as atherosclerosis in the carotid arteries (the large arteries that feed the brain and head). The cohort of middle aged adults includes an enlarged number of smokers so that the effects of smoking on atherosclerosis can be investigated with greater precision. Atherosclerosis is a disease of the artery wall that leads to most heart attacks and strokes. Change in an indicator of atherosclerosis (thickness of the two inner layers of arteries, the intima-media thickness, or IMT) has been measured noninvasively at 18 month intervals in the carotid arteries with 2-dimensional ultrasound. These repeated observations on the same participants have yielded a new look into the emergence of an effect of smoking and other factors on atherosclerosis in humans.

An effect of smoking on thickening of the inner two layers of the artery wall emerges in men, on average, in the age range 40-45 years. Emergence of a smoking effect in women is delayed until, on average, age 55-60 years. This delay in women is presumably due to protective factors associated with pre-menopausal hormones. The factors that delay a smoking effect on thickening of the artery wall in younger ages in men and women remain to be elucidated.

Current 2-dimensional ultrasound measurement of the carotid artery focuses on the combined intimal and medial layers. Atherosclerosis only involves thickening of the inner most layer (the intimal layer) of the artery wall.

A more desirable measurement of arterial wall thickening, from the perspective of studying the progress of atherosclerosis, would involve the measurement of intimal layer itself. The proposed study involves using a newly developed technique for computer processing of an ultrasound image to measure the thickness of the intima, separate from the media. The project involves re-processing the videotapes of repeated scans on 573 persons to determine the relations between this new measure and smoking. This new measurement may reveal new information concerning the causes and time-course of atherosclerosis and subsequent cardiovascular disease in response to smoking.

If the new measurement of intimal thickness proves to be superior to the current measurement of arterial wall thickness, then it may be feasible to use this measure for individual diagnosis and tracking. The current measurement is appropriate primarily for measurement of groups of persons.