LAUSR

Objective: Augmentation index (AIx) reflects aortic pressure augmentation and is independently associated with cardiovascular risk in adults. It is determined by structural and functional cardiovascular properties and increases with aging. This study examined AIx in terms of 24-hour variation, determining factors and association with indices of preclinical target-organ damage in young individuals. Design and method: Apparently healthy children, adolescents and young adults (age 10–25 years) referred for elevated blood pressure (BP) and healthy volunteers were subjected to: (i) 24-hour ambulatory monitoring of BP, central hemodynamics (including AIx adjusted to a heart rate of 75 bpm), and pulse wave velocity (PWV), using a noninvasive brachial cuff-based oscillometric device (Mobil-O-Graph 24 h PWA), and (ii) assessment of left ventricular mass index (LVMI) and common carotid intima-media thickness (cIMT). Results: Data from 108 untreated subjects were analyzed (mean age 17.8 ± 4.7 years, 86 males, body mass index 24.7 ± 5.1 kg/m2, 28 subjects with 24-hour BP > = 95th percentile for children/adolescents or > = 130/80 mmHg for adults). Females had higher 24-hour AIx than males (21.7 ± 3.9 vs. 12.7 ± 5.6%, p < 0.01; adjusted for height). Hypertensive subjects tended to have higher 24-hour AIx than normotensives (15.9 ± 7.1 vs. 14.1 ± 6.1%, p = NS). Daytime AIx was higher than nighttime (17.0 ± 7.7 vs. 10.4 ± 6.9% respectively, p < 0.01). Average nighttime dipping of AIx was 40.7% (77% of the subjects had >10% nocturnal dip). In children < 18 years (n = 59), 24-hour AIx was inversely associated with age (r = -0.28) and height (-0.54), whereas after the age of 18 years (n = 49), AIx was inversely related to height (-0.60), but positively to age (0.37). After adjustment for age, height and gender, partial correlation coefficients for AIx were as follows: r = 0.30/0.33 with 24-hour systolic/diastolic BP and r = 0.25 with 24-hour PWV (all p < 0.05), whereas no significant association was observed with LVMI and cIMT. Conclusions: These data suggest that in children AIx decreases with age until adulthood and increases thereafter. The effect of body height on AIx is stronger than that of aging. It appears that this index cannot be used as a surrogate index of cardiovascular risk at least until body height reaches its maximum.