Sex differences of carotid intima-media thickness in healthy children and adolescents
Introduction
In pediatric cardiovascular health prevention non-invasive diagnostics are of utmost importance for screenings and interventional purposes. Cardiovascular risk factors in childhood, such as obesity and hypertension [1], [2], [3] are the key issues for the development of subclinical cardiovascular disease [4].
The thickness of carotid artery intima-media (IMT) is an excellent surrogate marker of cardiovascular risk, used in stroke units and adult cardiology for non-invasive monitoring of the effect of therapeutic strategies [1], [5]. Several studies described increased IMT in children with known cardiovascular risk [6], [7], [8] and a “tracking” of those factors into adulthood [9]. The Cardiovascular Risk in Young Finns Study underlines hypertension as a major contributor to atherosclerosis emphasizing sex differences in predicting endothelial dysfunction [10].
In contrast to adulthood [11], [12], only little information exists regarding the age distribution of IMT in a healthy pediatric population, despite the need of early cardiovascular prevention.
A Japanese study [13] investigated the relationships between IMT and age in childhood analysing 60 healthy children (5–14 year) and described a linear increase of mean IMT with age. Sex differences of IMT as well as sex-specific percentiles, useful for follow-up studies, are not yet reported for a European pediatric cohort. Previous studies examined carotid IMT in a healthy population have generated conflicting results [14], [15], possibly due to methodological aspects.
Reference values of IMT in healthy German adults were described by others [16] who underlined higher IMT values for men in comparison to women for the age group 40–54 years. The present study emphasizes the determination of IMT percentiles in German children under strictly standardized sonographic conditions and analysis, using newest technologies. Knowing that sex differences exist in adults [16] and that IMT is associated with age [13], the objectives of this study were to investigate the following hypotheses: (i) the sonographic measurement is reliable and feasible in healthy children; (ii) there are sex differences in IMT in healthy children, requiring sex- and age-specific norm values; (iii) height, weight, BMI, the total percentage of body fat and blood pressure are associated with IMT and predictors for increased IMT in healthy boys and girls.
Section snippets
Subjects
267 children (143 girls and 124 boys, mean age girls 10.2 years (range 6–17 years); boys 10.8 years (range 6–17 years) from Munich schools were examined prospectively.
All legal representatives of the children provided written informed consent before examination. The study was approved by the Ethics Commission of the Technische Universität München, Germany (protocol number: 1162/04). According to personal questionnaires, all subjects were free from acute or chronic illnesses.
Anthropometry
Body weight,
Results
The characteristics of the sample population are displayed in Table 1. 11.9% of the girls were overweight and 5.6% underweight and 11.3% of the boys were overweight and 6.5% underweight. In girls, a significant increase of body fat (%) from age 10/11 to 12/13 years was illustrated (Fig. 3, supplementary appendix), whereas in boys a significant decrease of the percentage of body fat was demonstrated from age group 12/13 to 14/15 years (Fig. 4, supplementary appendix). This decrease of body fat
Discussion
In consideration of the fact that IMT is an important non-invasive marker of subclinical atherosclerosis and essential for screenings and interventional purposes, it is necessary to assess IMT percentiles in a well-controlled and well-characterized study group. Currently no data exist of a defined healthy German pediatric group that assessed IMT percentiles using a strict study protocol.
Regarding the feasibility, IMT ultrasound was easy to perform and well tolerated. Reliability was good
Conclusions
The results of this study provided reference values of IMT for both sexes for the age groups 8/9, 10/11, 12/13 and 14/15 years. Those sex differences are remarkable especially in the pubertal phase. Since in girls a continuous IMT increase could be documented with increasing age, in boys a stagnation of IMT was assessed at the age of puberty. The non-invasive sonography of IMT was easy to perform and well tolerated. IMT is affected by sex, age, body size, weight. Cardiovascular risk factors
Acknowledgement
We kindly acknowledge Raymonde Busch, Institute for Medical Statistics of the Technische Universität München, Germany for the statistical review of the paper and Dr. Dirk Sander, head physician, Medical Park Loipl, Hospital of Neurology, Bischofswiesen, Germany, for technical support relating to the off-line analysis of the ultrasound images and the allocation of the software macro. We thank the children and their parents, school principals and teachers for their support and participation.
The
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