Obese children and adolescents have elevated nighttime blood pressure independent of insulin resistance and arterial stiffness.

Background: Insulin resistance has been related to elevated blood pressure (BP) in obese children and may adversely affect the vasculature by arterial stiffening. The objective was to investigate whether daytime and nighttime BP were elevated and related to insulin resistance and arterial stiffness in obese children and adolescents.

Methods: Ninety-two obese patients aged 10-18 years were compared with 49 healthy control individuals. Insulin resistance was measured as the homeostatic assessment model (HOMA), and arterial stiffness was measured as carotid-femoral pulse wave velocity (cfPWV).

Results: Mean ± SD daytime systolic BP (SBP) (obese: 125±8.3mm Hg; control: 121±10.1mm Hg; P = 0.03) and nighttime SBP (obese: 108±10.7mm Hg; control: 102±8.2mm Hg; P = 0.0001) were higher in the obese group when compared with the control group. No difference was found in daytime diastolic BP (DBP), whereas nighttime DBP (obese: 60±6.6mm Hg; control: 57±4.8mm Hg; P = 0.001) and night-to-day BP ratios were higher in the obese group. Nighttime SBP was related to BMI z score (β = 6.0; 95% confidence interval (CI) = 2.9-9.1; P = 0.0002) and waist/height ratio (β = 36.7; 95% CI = 5.6-67.9; P = 0.02) in the obese group. HOMA index (obese: median = 3.7, interquartile range (IQR) = 2.3-6.0; control: median = 2.6, IQR = 1.8-3.4; P = 0.002) was higher, whereas cfPWV (obese: 4.8±0.8 m/s; control: 5.1±0.6 m/s; P = 0.03) was lower in the obese group. CfPWV was not related to logHOMA index. In multiple regression analyses, the higher nighttime BP in the obese group was independent of logHOMA and cfPWV.

Conclusions: Obese children had a higher nighttime BP when compared with the control group independently of insulin resistance and arterial stiffness. No relationship was found between insulin resistance and arterial stiffness. CLINICAL TRIAL REGISTRATION Clinicaltrials.gov identifier NCT01310088.