Associations of Hair Biomarkers with Height, Weight, and Body Mass Index in Preschool Children

Background: Adverse childhood experiences (ACEs) can lead to hypothalamic–pituitary–adrenal axis dysregulation, negatively impacting child growth and development. Methods: The Hair Biomarkers Study (HBS-I) evaluated healthy preschool children using parent-reported surveys, anthropometrics, and painlessly obtained scalp hair to measure hair cortisol (HCC; ng/mg) and oxytocin concentrations (HOC; ng/mg) via ELISA; log-transformed data were used in analyses. Height, weight, and BMI percentiles were based on CDC growth curves. Linear regressions examined associations of child and maternal hair biomarkers with percentiles, adjusting for sociodemographic factors. Results: The median age was 39.1 months (IQR 23.5–53.0, N = 1189). Higher child Ln-HCC was associated with an increased BMI percentile (0.027; 95%Cl: 0.013, 0.040), while higher child Ln-HOC was associated with a decreased BMI (−0.016; 95%Cl: −0.028, −0.005). Similar significant associations were observed between maternal biomarkers and child growth. In models mutually adjusted for mother and child hair biomarkers, maternal Ln-HCC was associated with an increased BMI percentile (0.036; 95%Cl: 0.003, 0.069), while maternal Ln-HOC was associated with a decreased BMI percentile (−0.034; 95%Cl: −0.052, −0.016). Maternal ACEs of 2–3 vs. 0–1 were associated with increased child weight (0.057; 95%Cl: 0.003, 0.112) and BMI percentiles (0.076; 95%Cl: 0.017, 0.135). Conclusions: We show that higher maternal and child HCC was associated with increased child BMI percentiles, while higher HOC was linked with decreased BMI percentiles. Hair biomarkers may reflect the effects of nurturing vs. adverse experiences during critical windows of growth and development in early childhood.