Relationship between body mass index z-score and blood pressure among children with overweight and obesity involved in a lifestyle modification program

Documenting the relationship between body mass index z-score (BMIz) and blood pressure (BP) is crucial to better position the importance of adiposity reduction in managing cardiometabolic risk in children. This study assessed the relationship between BMIz and systolic and diastolic BP (SBP, DBP) among children with overweight or obesity receiving lifestyle counseling at a pediatric obesity management clinic in Montreal (Province of Quebec, Canada). This is a retrospective, longitudinal analysis of medical records of 438 children (2-17 years). At the first clinic appointment, 181 (41.3%) children had normal BP, 85 (19.4%) had prehypertension, and 172 (39.3%) had hypertension. At baseline, each one-point increment in BMIz was associated with 28.3% (95% confidence interval (CI): 7.9, 52.6; <i>P</i> = 0.005) higher odds of prehypertension or hypertension. Between the first and the last appointment, each one-point decrease in BMIz was associated with a reduction of -6.24 percentiles (95% CI: -11.17, -1.32; <i>P</i> = 0.02) in SBP and -4.99 percentiles (95% CI: -9.31, -0.66; <i>P</i> = 0.03) in DBP. Children who experienced BMIz reduction of -0.25 or more were more likely to achieving SBP reductions of -3.20 mmHg or more relative to those smaller BMIz changes (OR: 2.00, 95% CI: 1.23, 3.25; <i>P</i> = 0.006). Baseline BMIz, but not changes in BMIz over follow-up, was negatively associated with odds of normalizing BP among the 257 children with prehypertension or hypertension at baseline (OR: 0.70, 95% CI: 0.54, 0.91; <i>P</i> = 0.007). This study leveraged real-world clinic data to provide further importance on adiposity reduction in pediatric cardiometabolic risk management.