The correlation between neonatal vitamin D levels and the risk of childhood asthma attacks
Authors: Ling Yang
Lihua Zhong
Wei Zhang
Kaihui Xing
Qiuli Chen
Shen Liu
Jin Zhou
Wenlin Li
Journal: Translational Pediatrics (2021)
Discipline: CLINICAL MEDICINE
Keywords: Newborns; asthma; children; vitamin D.
Affiliations: Department of Neonatology, Haikou Hospital of The Maternal And Child Health, Haikou, China., Department of Pediatrics, Haikou Hospital of Maternal and Child Health, Haikou, China.

Abstract:  Background: To explore the correlation between neonatal vitamin D levels and the risk of asthma in children aged 3-9 years. Methods: A total of 1,534 subjects were selected, and clinical and laboratory test data of all subjects were collected at birth, including 25-hydroxyvitamin D3 [25(OH)D3] levels, gender, season of birth, birth weight; whether delivery was premature, cesarean section, or primipara; and parental details including maternal age, ethnicity, level of education, history of smoking, and history of maternal or paternal asthma. The level of 25(OH)D3 was used as a continuous variable to analyze its correlation with the risk of asthma using the Cox proportional regression model. In addition, subjects were divided into four groups according to their 25(OH)D3 quartiles, and the first quantile group was used as a reference to analyze the risk of asthma in the other groups. Further subgroup analysis was conducted according to the patients' gender and birth season. Results: Among the 1,534 subjects included, there were 107 cases in the asthma-affected group and 1,427 cases in the normal control group. Compared with the control group, the level of 25(OH)D3 in the asthma group was significantly lower (P=0.03), the mother's education level was lower (P=0.002), but the preterm birth rate, cesarean section rate, and parental asthma prevalence rate were significantly higher (all P&lt;0.05). When the neonatal 25(OH)D3 was divided into quartiles to perform a categorical variable analysis, we found that compared with the first quantile (Q1, 0.0-25.1 mmol/L), the risk of asthma in Q4 was reduced by 50% (HR=0.50, 95% CI: 0.38-0.76). The second quantile group (Q2) and the third quantile group (Q3) showed no significant difference in the risk of disease compared with Q1 but showed a trend of decreasing risk as the quantile group increased (the trend P values were both &lt;0.05). This correlation was still valid when a stratified analysis was made based on gender and birth season. Conclusions: There is a significant correlation between a reduced vitamin D level in newborns and the subsequent risk of asthma in children aged 3-9 years. Moreover, the level of vitamin D is an independent risk factor for childhood asthma. 

Retracted: No

PubPeer comments:
 If I understand the methods correctly the authors used a proportional hazard model where covariates are multiplicatively related to the hazard. The quasi linear relationship shown in Fig 1 is unlikely from their HR s, eg Q2 must be 1 while they even don t have enough data to plot a curve 80 nmol L. I would have also preferred ORs over HRs. ![file] Asthma children have more asthma parents who avoid more outdoor exposure resulting in slightly lower (-6 nmol L) vitamin D serum values. Where is the physiological relevance ? there was no significant difference in long-term risk (at age 6) (OR =1.21, 95% CI: 0.63u20132.32) (29,30). references are wrong ,