[Association of vitamin D deficiency with severity of symptoms in children with vasovagal syncope]

Objective: To investigate the correlation between vitamin D deficiency and the severity of symptoms in children with vasovagal syncope (VVS). Methods: A prospective study was conducted. One hundred and twenty-two children diagnosed with VVS by head up tilt test in Department of Pediatric Cardiology and 130 healthy children without symptoms who underwent physical examination in the outpatient department of Child Healthcare Department of Second Hospital of Lanzhou University from December 2019 to May 2021 were selected and assigned to VVS group and control group, respectively. According to the diagnostic criteria of vitamin D deficiency, children in the VVS group were assigned to three subgroups: non-vitamin D deficiency, vitamin D deficiency, and severe vitamin D deficiency. All children underwent detailed history taking, physical examination, and level determination of serum 25 (OH) D. Children in the VVS group were scored for orthostatic intolerance (OI) symptoms including 10 symptoms: syncope, dizziness, nausea, palpitation, headache, tremor, chest tightness, blurred vision, profuse perspiration, and attention deficit. The differences in the age, gender, body mass index, blood pressure, and serum 25 (OH) D levels between VVS group and control group, and the differences regarding the age, gender, body mass index, blood pressure, serum 25 (OH) D levels and symptom scores among the three VVS subgroups were compared. Comparisons were performed using independent sample t test, ANOVA analysis, Chi square test and rank sum test. Pearson correlation analysis was used to analyze the correlation between serum 25 (OH) D levels and OI symptom scores in children with VVS. Results: The serum 25 (OH) D levels were significantly lower in the VVS group than those in the control group ((31±11) vs. (46±10) nmol/L, t=10.89, P<0.001). Vitamin D deficiency was more frequent in the VVS group (73.0% (89/122) vs. 24.6% (32/130), χ²=58.91, P<0.001). There were significant differences among the severe vitamin D deficiency subgroup, vitamin D deficiency subgroup, and non-vitamin D deficiency subgroup regarding the serum 25 (OH) D levels ((9.8±0.4) vs. (26.6±6.5) vs. (45.8±5.9) nmol/L, F=142.77, P<0.001) and the OI symptom scores ((14±1) vs. (10±2) vs. (7±2) scores, F=44.97, P<0.001). The scores of syncope, nausea, profuse perspiration, blurred vision and dizziness among the severe vitamin D deficiency subgroup, vitamin D deficiency subgroup, and non-vitamin D deficiency subgroup were statistically significant (H=9.01, 7.52, 12.11, 7.07 and 9.54, respectively, all P<0.05). Pearson correlation analysis showed that the serum 25 (OH) D levels were negatively correlated with OI symptom scores in children with VVS (r=-0.769, P<0.001). Conclusions: VVS children have significant vitamin D deficiency. The severity of symptoms increases with decreasing of vitamin D level. Syncope, nausea, and profuse perspiration are more likely to occur in children with severe vitamin D deficiency, and dizziness and blurred vision are more likely to occur in children with vitamin D deficiency.