Ultrasonic evaluation of common carotid intima-media thickness (IMT)--influence of local plaque on the relationship between IMT and age.

Ultrasonic evaluation of the intima-media thickness in the common carotid artery (IMT-CCA) has been widely used as a marker of atherosclerosis. However, the definition of IMT-CCA is not uniform and it includes two quite different pathological changes; a general intima-media thickening and a local atherosclerotic change (plaque formation). The aim of this paper was to evaluate the IMT-CCA and local atherosclerosis separately, and to clarify how the IMT-CCA itself changes with age and how local plaques influence the relationship between the IMT-CCA and age. The subjects were 979 men and women aged 40 to 79 years who participated in the first wave examination of the National Institute for Longevity Sciences--Longitudinal Study of Aging (NILS-LSA). The IMT-CCA measured at the thinnest point was significantly higher in men (0.61 +/- 0.15 mm) than in women (0.58 +/- 0.14 mm, p < 0.01) and it increased with age (trend p < 0.0001) in both genders. The IMT-CCA was higher with the presence of plaque in the bulbs (PLQ-BLB) than without PLQ-BLB (p < 0.0001). Although this was a cross-sectional study, the IMT-CCA increased 0.06 mm/10 years with PLQ-BLB and 0.04 mm/10 years without PLQ-BLB. The IMT-CCA could be partially explained by age, gender and PLQ-BLB (r2 = 0.317). In this middle-aged and elderly population, an increase in the IMT-CCA showed a moderate relationship with local atherosclerosis and age.