Objectives: To investigate during adolescence (1) sex differences in blood pressure (BP) and hemodynamic factors at rest and during physical and mental challenges and (2) whether these differences are mediated by body composition and glucose and lipid metabolism.
Design: Cross-sectional study of a population-based cohort.
Setting: Saguenay Youth Study, Quebec, Canada, from November 2003 to June 2007.
Participants: A total of 425 adolescents (225 girls aged 12-18 years).
Outcome measures: Systolic and diastolic BP measured using a Finometer. Secondary outcome measures were (1) hemodynamic parameters also measured with a Finometer, (2) body composition assessed with magnetic resonance imaging, bioimpedance, and anthropometry, and (3) metabolic indices determined from a fasting blood sample.
Results: Girls vs boys demonstrated lower systolic and diastolic BP at rest and during challenges, with the differences being greatest during a math-stress test (adjusted difference, 7 mm Hg; 95% confidence interval [CI], 4-10 mm Hg and adjusted difference, 6 mm Hg; 95% CI, 4-8 mm Hg, respectively). The differences were mainly due to girls vs boys having lower stroke volume while lying down, standing (adjusted difference, 4 mL; 95% CI, 1-7 mL), and sitting, and lower total peripheral resistance during the math-stress test (adjusted difference, 0.14 mm Hg . s/mL; 95% CI, 0.09-0.21 mm Hg . s/mL). Intra-abdominal fat was positively associated with BP, but less in girls than in boys, and fat-free mass, fat mass, and insulin resistance were also positively associated with BP, similarly in boys and girls.
Conclusions: In adolescence, BP is lower in girls than boys, with the difference being determined mainly by lower stroke volume during physical challenges and by lower total peripheral resistance during mental challenges. Body composition and insulin resistance contribute to these differences.