Washington, Sept 23 : A study has found that lower levels of vitamin D may cause structural changes in the airway muscles of children with STRA, making breathing more difficult.

Children with severe therapy-resistant asthma (STRA) may have poorer lung function and worse symptoms compared to children with moderate asthma, due to deficiency of vitamin D in their blood.

"This study clearly demonstrates that low levels of vitamin D are associated with poorer lung function, increased use of medication, worse symptoms and an increase in the mass of airway smooth muscle in children with STRA," said Atul Gupta, MRCPCH, M. D., a researcher from Royal Brompton Hospital and the National Heart and Lung Institute (NHLI) at Imperial College and King''s College London.

"It is therefore plausible that the link between airway smooth muscle mass and lung function in severe asthma may be partly explained by low levels of vitamin D," he said.

The researchers enrolled 86 children in the study, including 36 children with STRA, 26 with moderate asthma and 24 non-asthmatic controls, and measured the relationships between vitamin D levels and lung function, medication usage and symptom exacerbations.

The researchers also examined tissue samples from the airways of the STRA group to evaluate structural changes in the airway''s smooth muscle.

At the conclusion of the study the researchers found children with STRA had significantly lower levels of vitamin D, as well as greater numbers of exacerbations, increased use of asthma medications and poorer lung function compared to children with moderate asthma and non-asthmatic children. Airway muscle tissue mass was also increased in the STRA group.

"The results of this study suggest that lower levels of vitamin D in children with STRA contribute to an increase in airway smooth muscle mass, which could make breathing more difficult and cause a worsening of asthma symptoms," Dr. Gupta said.

The findings suggest new treatment strategies for children suffering from difficult-to-treat asthma, he added.

But before any widespread treatment recommendations can be made, however, larger studies will need to be conducted to confirm the results, he added.

The findings were published online ahead of the print edition of the American Thoracic Society''s American Journal of Respiratory and Critical Care Medicine. (ANI)