Vitamin D Deficiency and Asthma Morbidity in School-Age Children: A Single-Centre Cohort Study

Lijuan Dong^*Yan Li

• Department of Pediatrics, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, 710000, China

Background: Asthma remains a major cause of morbidity among school-age children worldwide, with deficiency of vitamin D increasingly recognized as a modifiable factor influencing immune regulation and respiratory health. However, evidence on its association with asthma control and exacerbation patterns in pediatric populations is limited, in low-and middle-income population. Methods: A retrospective single-center study of 320 children, 6–14 years, diagnosed with asthma between January 2019 and December 2023. Following application of inclusion and exclusion criteria, 210 children were analyzed. Data were obtained from medical records and structured questionnaires, including socio-demographic characteristics, asthma control status, exacerbation frequency, hospitalization history, and biochemical assays (serum vitamin D, calcium, phosphate, parathyroid hormone). Patients were categorized as vitamin D deficient, insufficient, or sufficient. Statistical analyses, including χ² tests, ANOVA, and multivariable logistic regression, were performed using R (v4.3.2). Results: Vitamin D deficiency was prevalent in 45.2% of children, while 31.0% were insufficient and 23.8% sufficient. Poor asthma control was more common among deficient children (63.2%) compared to insufficient (43.1%) and sufficient groups (24.0%). The mean annual exacerbation rate was highest in the deficient group (2.6 ± 1.3) versus insufficient (1.9 ± 1.1) and sufficient groups (1.1 ± 0.9). Hospitalization rates also differed significantly (31.6%, 18.5%, and 12.0%, respectively; p = 0.014). Multivariable logistic regression confirmed that vitamin D deficiency independently predicted poor asthma control (adjusted OR 2.8, 95% CI 1.6–4.9, p < 0.001) after adjustment for age, sex, BMI, and treatment profile. Conclusion: Vitamin D deficiency is highly prevalent among school-age children with asthma and is independently associated with poor control, higher exacerbation frequency, and increased hospitalizations. As part of integrated pediatric asthma care, these findings emphasize the significance of routine screening and the need to take vitamin D supplements into account. At the public health level, targeted nutritional interventions may reduce disease burden and improve long-term outcomes in children.