Introduction: Asthma is one of the commonest chronic respiratory disorders in children, influenced by environmental, perinatal, genetic, and nutritional factors. Vitamin D, has essential immunomodulatory functions apart from its role in bone health. Vitamin D has its implications in asthma pathogenesis and control. This study was conducted to assess the serum vitamin D levels in asthmatic and non-asthmatic children, and also to evaluate its correlation with lung function, and the role of associated risk factors. Materials and Methods: A hospital-based cross sectional, comparative study was conducted after obtaining Institutional Ethical committee approval. The study was conducted among 50 asthmatics and 50 age- and sex-matched non-asthmatic controls in the age group of 5–16 years. Baseline demographic and anthropometric data were recorded. The environmental risk factors perinatal history, familial history were obtained from the participants. Pulmonary function parameters (FVC, FEV1, FEV1/FVC, PEFR, FEF25–75) were measured by spirometry following American Thoracic Society (ATS) guidelines. Serum vitamin D levels were determined using a standard immunoassay. Age-appropriate oral or written assent was obtained from the parents. Results: The results showed significantly lower mean vitamin D levels in asthmatic children (15.75 ± 4.46 ng/ml) when compared to controls (18.85 ± 3.98 ng/ml; p < 0.001). FEV1 and FEV1/FVC ratios were significantly decreased in asthmatic children (p < 0.001). Positive associations with asthma were observed in preterm birth babies (p = 0.011), parental history (p = 0.026), and passive smoking (p < 0.001). There was a significant positive correlation of vitamin D levels with FEV1/FVC ratio overall (r = 0.473), in controls (r = 0.388), and in cases (r = 0.333). Conclusion: Positive associations with asthma and lung function were observed with lower vitamin D levels. Addressing the vitamin D deficiency along with modifiable risk factors such as passive smoking may improve the control of asthma. Further research are warranted to establish the therapeutic and preventive role of vitamin D deficiency in childhood asthma.
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