Gender-related differences in the relationships between blood pressure, age and body size in pre-pubertal children

Background: The blood pressure increase with age is well documented in adults and children. However, in the paediatric age group, body size is the most important determinant of age-related blood pressure increases. Aim of the present analysis was to investigate the relationships between age, gender and body size and blood pressure (BP) in children. Methods: To this purpose, data were analysed from 4514 prepubertal children, aged 6-11 years (71% of the eligible sample; M=2283, F=2231) from the ARCA Project, a screening of childhood obesity carried out in Southern Italy. Girls who reported the occurrence of menarche were excluded from the analysis. The sample constituted roughly 20% of all the children attending the primary schools in the area. Weight, height, waist circumference and BP were measured according to standardised procedures. Results: As expected, both systolic and diastolic BP significantly increased (P<0.001) with age in boys and girls. However, after adjustment for waist circumference (as index of adiposity) and height (as index of body size), BP significantly increased with age only in girls (systolic BP: F=4.380, P=0.002; diastolic BP: F=3.093, P=0.01;) but not in boys (systolic BP: F=0.711, P=0.55; diastolic BP: F=2.180, P=0.07). The association, however, was no longer apparent after the exclusion of children aged >10 years. Conclusions: In prepubertal girls in the age range 6-11 years, but not in boys, age is significantly associated with blood pressure independently of body size and adiposity.