Serum Vitamin D Levels in Children and Adolescents with Vasovagal Syncope, Syncope Due to Orthostatic Hypotension, and Cardiac Syncope

Objective: The study aimed to compare vitamin D levels between children and adolescents with vasovagal syncope, syncope due to orthostatic hypotension, cardiac syncope, and healthy individuals and to investigate the correlations of 25(OH)D with main clinical parameters of syncope. Materials and Methods: This study involved 83 children aged 8-17 years with syncope: 40 with vasovagal syncope, 24 with syncope due to orthostatic hypotension, and 19 with cardiac syncope. There were 24 healthy volunteers in the control group. Data concerning active standing test, electrocardiography, echocardiography, electroencephalography, and 24-hour Holter monitoring findings were collected. Serum vitamin D was evaluated by an enzyme-linked immunoassay technique test. Results: The mean levels of serum 25(OH)D were decreased in children with vasovagal syncope (18.8 +/- 5.9 ng/mL), syncope due to orthostatic hypotension (19.9 +/- 6.7 ng/mL), and cardiac syncope (20.6 +/- 7.3 ng/mL) in comparing with the control group (30.9 +/- 5.9 ng/mL; P <.001). In patients with syncope due to orthostatic hypotension, vitamin D deficiency was associated with a reduction in systolic blood pressure (r = 0.43) and diastolic blood pressure (r = 0.38) within the first minute, lower systolic blood pressure (r = 0.44) within the third minute of active orthostasis (P <.05). There were significant correlations of vitamin D deficiency with parameters of cardiac autonomic activity pNN50 (r = 0.49), total power (r = 0.39), and low frequency index (r = 0.35) in children with cardiac syncope (P <.05), while heart rate variability was not affected in patients with vasovagal syncope and syncope due to orthostatic hypotension (P >.05). Conclusion: Children and adolescents with vasovagal syncope, syncope due to orthostatic hypotension, as well as cardiac syncope had higher frequency of vitamin D deficiency than healthy pediatric controls. This provides a new approach to syncope management in pediatric population, requiring further studies.