[Aging and ultrasonographic findings of carotid atherosclerosis]

To establish the prevalence of carotid atherosclerosis and its relation to aging in Japanese population, 270 participants in voluntary health screening at our hospital were studied with 7.5 MHz B-mode ultrasonography and accelerated plethysmography (APG), and their levels of serum lipids were measured. The subjects consisted of 84 people in the fifth decade of life, 89 in the sixth decade, 67 in the seventh decade, and 30 in the eighth decade. Carotid lesions were deemed to be present when occlusion, atheromatous plaque, or both were found. Atheromatous plaque was defined as a thickened intima-media complex of 2.1 mm or more. Plaques were divided into two types based on morphometric criteria, and into three types based on echogenic criteria. Thickness of the intimamedia complex (IMT) was measured at two randomly chosen points along the common carotid artery. APG was obtained by double-differentiation of finger-plethysmograph record, and the APG index was calculated as (-b+c+d)/a, where the letters are the distances from the baseline to the peaks of each wave (a, b, c, and d waves) on the APG waveform. Carotid lesions were seen in 5% of subjects in the fifth decade of life, 7% of subjects in the sixth decade, 24% of those in the seventh decade, and 27% of those in the eighth decade. All the lesions were plaques, and neither plaque type nor size differed between young-adult and elderly subjects. Multiple regression analysis revealed that the thickness of the intima-media complex correlated significantly with age, but not with carotid lesions, sex, body weight, serum lipid levels, hemoglobin A1 level, or uric acid level. The APG index also decreased significantly with age, but no correlation was seen with carotid lesions or with the thickness of the intima-media complex. These findings indicate that people aged 60 or over could be at risk for plaque formation in the carotid arteries and their carotid arteries should be examined carefully even in the absence of risk factors for vascular disease. These findings also suggest that both increased thickness of the intima-media complex and a low APG index arise via pathophysiologic mechanisms different from those that lead to atheromatous plaque.