Vitamin D status and its association with asthma control and severity in children.

Introduction: Vitamin D has an immunomodulatory effect on innate and adaptive immunity within the body, which partially explains its links to inflammation-induced epithelial changes seen in asthma. Various evidence suggest a potential link between vitamin D deficiency and asthma control and severity. This study aimed to determine the vitamin D levels in asthmatic children and their association with asthma severity and control.

Materials and methods: A cross-sectional prospective study was conducted on 72 children with persistent asthma aged 5 to 18 years old in a tertiary hospital in Kelantan. Asthma severity was assessed using the Global Initiative for Asthma (GINA) guidelines based on treatment given. Asthma control was evaluated using both parent/patient self-administered Asthma Control Test (ACT) or Children's Asthma Control Test (c-ACT) scores accordingly to their age and asthma control GINA classification. Serum 25-hydroxyvitamin D [25(OH)D] levels were measured, with <52 nmol/L defined as deficient and 52-73 nmol/L as insufficient.

Results: Of the 72 children with persistent asthma, 40.3% had vitamin D deficient and 38.9% had vitamin D insufficient with a mean 25(OH)D level of 58.74 nmol/L. Being female, older age group and higher body mass index (BMI) were associated with vitamin D deficiency (p =<0.05). Lower vitamin D levels were significantly associated with increased asthma severity (p =0.020). There was no significant association between vitamin D levels and asthma control based on GINA classification (p =0.470) and c-ACT/ACT scores (p =0.052).

Conclusion: High prevalence of vitamin D deficient and insufficient was found among children with persistent asthma. Vitamin D deficiency was significantly associated with increased asthma severity. This group of children needs further evaluation for intervention. We recommend routine assessments of vitamin D levels among children with moderate to severe asthma.