In adults, arterial distensibility decreases with age and relates to changes in cardiac left ventricular mass. Longitudinal data on changes in arterial distensibility from childhood to adulthood are lacking. Our aim was to study the effect of age and sex, and low-saturated fat dietary counseling on arterial distensibility from childhood to early adulthood. In addition, we assessed the association of arterial distensibility with left ventricular mass. Distensibility of the

abdominal aorta and common carotid artery was measured repeatedly at ages 11, 13, 15, 17, and 19 years (n=395–472) in an atherosclerosis prevention trial (Special Turku Coronary Risk Factor Intervention Project [STRIP]). Aortic and carotid distensibility decreased with age (both P<0.0001). In boys, distensibility values were generally lower (P<0.0001) and showed steeper decrease by age (age and sex interaction: both P<0.01). The low-saturated fat dietary counseling given in STRIP was not significantly associated with arterial distensibility. Left ventricular mass increased with age (P<0.0001), and it was greater in boys (P<0.0001). In conclusion, a marked age-related decrease in vascular distensibility was found already at this young age, and this decrease was more pronounced in boys than girls. The longitudinal progression of aortic and carotid distensibility was related with changes in left ventricular mass.