Efficacy and Safety of Oral Vitamin D supplementation on pulmonary function parameters assessed by forced oscillation technique in children with bronchial asthma: A pilot, double blind, randomized trialâ€

Asthma is chronic inflammatory disorder of the airways that causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough, particularly at night or in the early morning; associated with variable bronchoconstriction and airflow limitation. Over a period of time in countries with comparable levels as India, an increase of up to 3% over a period of 10 years is seen.  As per Global Asthma Network phase-1 study the overall prevalence (range) of symptoms in adults was 4.4% (0.9–29.0%) for asthma ever and 10% adolescent and children have asthma ever with considerable variation across different countries. The recent Global Burden of Disease (GBD, 1990–2019) estimated the total burden of asthma in India as 34.3 million, accounting for 13.09% of the global burden. It also attributed that there were 13.2 per thousand deaths due to asthma in India. Asthma accounted for 27.9% of disability-adjusted life years (DALYs) in the Indian population.

Acute exacerbation of asthma is an emergency condition. It is defined as acute or subacute worsening of symptoms and lung function compared with the patient’s normal status and requiring a change in treatment or hospitalisation. The mainstay treatment for acute asthma includes inhaled beta2 agonists, ipratropium bromide and inhaled or systemic steroids, oxygen therapy, and need for hospitalizations. More than 50% of guidelines evaluated the need for reliever medication and lung function assessment (peak expiratory flow (PEF) or forced expiratory volume in 1 s (FEV1)) as tools for assessing asthma control.

Evidence suggests that patient with bronchial asthma who have vitamin D deficiency are associated with increased airway hyper-responsiveness, reduced pulmonary functions, poor asthma control, and reduce steroid responsiveness.

Active form of vitamin D (1- 25[OH]2D) is also critical in immune regulation, and deficiency of this vitamin has been linked to both autoimmune disease and cardiovascular disease. In addition, the vitamin D axis has been implicated in the pathogenesis of chronic respiratory diseases including asthma and chronic obstructive pulmonary disease (COPD). Vitamin D also act as immunomodulator and anti-inflammatory.

A study on pre-and postnatal VDD found that prenatal VDD caused diminished tracheal diameter, tracheal cartilage thickness and alveolar simplification which led to increased airway resistance.

Currently we lack conclusive evidence regarding the effect of vitamin D supplementation in children with bronchial asthma to improve lung function. Most of the previously done studies have seen effect of vitamin supplementation with spirometry parameters and asthma control test. As literature suggest that spirometry is not enough sensitive for small airways and spirometry parameters does not reflect airway resistance and reactance which is best measured by forced oscillation technique. As multiple studies have shown the effect of vitamin D on airway and lung structure. Only a few studies have examined the role of oral vitamin D supplementation therapy in bronchial asthma among children. There are several limitations in methodology of these studies however there are encouraging results with oral vitamin D being more effective in improving lung function parameters, decreasing exacerbation, hospital visit, need of oral corticosteroid use without adverse effect of vitamin D supplementation.