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25-09-2011 | General practice | Article

Vitamin D deficiency linked to reduced lung function in severe childhood asthma

Abstract

Free abstract

MedWire News: Children with severe therapy-resistant asthma (STRA) have significantly reduced levels of vitamin D, which are associated with an increase in airway smooth muscle (ASM) mass, poorer lung function, and increased medication use, research shows.

"Our results suggest that detecting vitamin D deficiency in children with STRA, and then treating that deficiency, may help prevent or reduce the structural changes that occur in the ASM, which in turn may help reduce asthma-related symptoms and improve overall lung function," said lead researcher Atul Gupta, from the Royal Brompton Hospital in London, UK.

The findings, published in the American Journal of Respiratory and Critical Care Medicine, come from a study of 36 children with STRA, 26 with moderate asthma (MA), and 24 without the condition (controls), aged between 6 and 16 years.

Blood samples were collected from the children and assessed for serum levels of 25-hydroxyvitamin D (25[OH]D3).

They were also assessed for medication use, acute exacerbations in the previous 6 months, symptom control (Asthma Control Test [ACT]), and lung function (spirometry).

The team found that children with STRA had significantly lower serum 25[OH]D3 levels than those with MA, who, in turn, had significantly lower levels than controls, at 28.0, 42.5, and 56.5 nmol/l, respectively.

The prevalence of vitamin D deficiency (<50nmol/l) in STRA patients, MA patients, and controls was 94%, 54%, and 33%, respectively, while the prevalence of 25[OH]D3 deficiency (<75nmol/l) was 97%, 92%, and 83%, respectively.

Analysis revealed a positive association between 25[OH]D3 levels and percent of predicted forced expiratory volume in 1 second and forced vital capacity in all participants.

In patients with STRA and MA, 25[OH]D3 levels were positively associated with ACT scores, and inversely associated with number of exacerbations in the previous 6 months, inhaled corticosteroid dose, and ASM mass (an indicator of airway remodelling).

The researchers also noted an inverse association between ASM mass and ACT scores in the asthma patients.

Gupta concluded: "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 ASM in children with STRA.

"It is therefore plausible that the link between ASM mass and lung function in severe asthma may be partly explained by low levels of vitamin D."

By Mark Cowen

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