The decline of vitamin D in adolescent athletes: insights from a one-year follow-up and its association with electrocardiographic changes.

Introduction: Annual health evaluations are essential for athletes to ensure fitness for competition and enable the early detection of emerging health issues. Aim: This research aimed to evaluate the longitudinal variations in vitamin D concentrations and associated physical and laboratory parameters among adolescent athletes, as well as to investigate their correlation with electrocardiographic (ECG) alterations following a one-year follow-up period. Subjects and methods: This prospective observational cohort study examined 93 adolescent male athletes (aged 11.6 ± 1.15 years, range 10-14) who underwent baseline health evaluations, including physical examination, laboratory tests [25(OH) vitamin D, parathyroid hormone, and muscle enzyme assays], and cardiovascular (CV) assessment with electrocardiography (ECG). Only patients with normal CV findings were included. Follow-ups were performed after one year. Results: At follow-up, weight, height, and muscle mass increased significantly, whereas fat mass and systolic pressure decreased. Vitamin D levels declined (21.9 ± 10.8 vs. 29.8 ± 8.6 ng/mL; p < 0.001), with compensatory rise in parathyroid hormone (38.8 ± 2.7 vs. 33.9 ± 1.6 pg/mL; p < 0.001). Among vitamin D-deficient athletes (n = 79), ECG changes occurred in 26.6%, mainly sinus arrhythmia (15/79, 19%) and T-wave inversion (13/79, 16%). Vitamin D deficiency was associated with higher odds of T-wave inversion (OR 4.53; 95% CI 1.11-18.40; p = 0.035) and increased prevalence of U-wave and incomplete right bundle branch block. Conclusions: The drop in vitamin D levels over one year raises concerns, highlighting the need for monitoring and interventions due to vitamin D's role in musculoskeletal and CV health. Regular monitoring and preventive strategies are recommended to maintain optimal vitamin D levels and CV health among young athletes.