Intima-media thickness and arterial function in obese and non-obese children

Data collection was part of the prevention project “Sternstunden der Gesundheit”, a prospective cross-sectional study conducted from October 2012 to July 2013 in the area of Berchtesgadener Land, Germany. 1017 healthy children (483 boys/534 girls) aged 7–18 were examined to establish reference values for cIMT and parameters of arterial distensibility [15]. Children had no history of chronic disease or signs of acute infection. The study was approved by the ethics committee of the Technische Universität München (5490/12), written informed consent was obtained from parents and from parents and children???14 years.

Out of the total study population, n?=?46 children (27 girls) were obese, according to German reference values which define obesity as BMI SDS above the 97^th percentile [16]. Obese children were compared with n?=?46 sex- and age-matched normal weight controls.

Anthropometric measurements were performed by trained staff according to standardized guidelines [17]. Body weight was measured without shoes, wearing light clothes to the nearest 0.1 kg, body height was measured with a stadiometer (seca 799, seca, Hamburg, Germany), standing upright without shoes to the nearest 0.1 cm. Body-Mass-Index (BMI) was calculated from the ratio of mass (kg) to height² (m²).

cIMT and distensibility were assessed using semi-automated B- and M-Mode ultrasound, (ProSound Alpha 6, Aloka/Hitachi Medical Systems GmbH, Wiesbaden, Germany) with a high frequency linear array probe (5–13 MHz). After 15 min rest patients were examined in supine position, the neck slightly extended and their head turned 45° opposite the site being scanned. cIMT was measured in B-Mode according to the Mannheim consensus [18] on the common carotid artery (CCA) far wall, 1 cm proximal to the bulb at end-diastolic moment. The cardiac cycle was simultaneously controlled with a 3 lead ECG. Of each subject, four measurements were performed, two on the left and two on the right CCA and calculated as average mean value of four measurements.

Distensibility was assessed in real time M-Mode with high precision vascular echo tracking at the same location than cIMT. Two tracking gates were placed on the CCA near and far wall which followed vessel wall motion, thereby calculating diameter change during heart cycles. Four video loops of at least five heart cycles were stored, two for the left and two for the right CCA. Distensibility parameters were calculated as average mean value of four measurements. As distensibility is pressure dependent [19], blood pressure (BP) was measured oscillometrically on the left arm (Mobil-O-Graph®, I.E.M., Stolberg, Germany) after 10 min rest, and applied in the calculation. Hypertension was defined as BP SDS above the 95^th percentile according to German reference values [20].

In general, PWV is the speed at which the forward pressure wave is transmitted from the aorta through the vascular tree. In this study, PWV ? is assessed as CCA local pulse wave velocity, calculated from ?.

All measurements were performed by two experienced examiners. The coefficient of variation (CV) between both examiners, assessed in 27 subjects, was 4.79 for cIMT, and 3.54 % for distensibility, calculated as average CV of AC (4.47 %), Ep (3.42 %), ? (4.92 %) and PWV ? (1.37 %).

Data was analyzed using IBM SPSS statistics for Windows, version 21.0 (SPSS, Inc., Chicago, IL, USA). After testing for normal distribution, differences between obese and normal weight children were analyzed by independent samples t-test or Mann–Whitney U-test, for boys and girls separately. The independent influence of BMI and BP on vascular data was analyzed by multivariate stepwise linear regression, and the association with BMI by bivariate correlation, controlled for sex, age, and BP. A P-value of 0.05 was considered to be statistically significant.