Low levels of vitamin D are associated with lower lung function and greater medication use in children with asthma

Low Vitamin D Levels Associated With More Asthma Symptoms and Medication Use

ScienceDaily (Apr. 20, 2010) — Low levels of vitamin D are associated with lower lung function and greater medication use in children with asthma, according to researchers at National Jewish Health. In a paper published online this week in the Journal of Allergy & Clinical Immunology, Daniel Searing, MD, and his colleagues also reported that vitamin D enhances the activity of corticosteroids, the most effective controller medication for asthma.

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"Asthmatic children in our study who had low levels of vitamin D were more allergic, had poorer lung function and used more medications," said Dr. Searing. "Conversely, our findings suggest that vitamin D supplementation may help reverse steroid resistance in asthmatic children and reduce the effective dose of steroids needed for our patients."

The researchers examined electronic medical records of 100 pediatric asthma patients referred to National Jewish Health. Overall, 47 percent of them had vitamin D levels considered insufficient, below 30 nanograms per milliliter of blood (ng/mL). Seventeen percent of the patients had levels below 20 ng/mL, which is considered deficient. These levels were similar to vitamin D levels found in the general population.

Patients low in vitamin D generally had higher levels of IgE, a marker of allergy, and responded positively to more allergens in a skin prick test. Allergies to the specific indoor allergens, dog and house dust mite, were higher in patients with low vitamin D levels. Low vitamin D also correlated with low FEV1, the amount of air a person can exhale in one second, and lower FEV1/FVC, another measure of lung function. Use of inhaled steroids, oral steroids and long-acting beta agonists were all higher in patients low in vitamin D.

"Our findings suggest two possible explanations," said senior author Donald Leung, MD, PhD. "It could be that lower vitamin D levels contribute to increasing asthma severity, which requires more corticosteroid therapy. Or, it may be that vitamin D directly affects steroid activity, and that low levels of vitamin D make the steroids less effective, thus requiring more medication for the same effect."

The researchers performed a series of laboratory experiments that indicated vitamin D enhances the action of corticosteroids. They cultured some immune cells with the corticosteroid dexamethasone alone and others with vitamin D first, then dexamethasone. The vitamin D significantly increased the effectiveness of dexamethasone. In one experiment vitamin D and dexamethasone together were more effective than 10 times as much dexamethasone alone.

The researchers also incubated immune-system cells for 72 hours with a staphylococcal toxin to induce corticosteroid resistance. Vitamin D restored the activity of dexamethasone. "Our work suggests that vitamin D enhances the anti-inflammatory function of corticosteroids,' said Dr. Leung. "If future studies confirm these findings vitamin D may help asthma patients achieve better control of their respiratory symptoms with less medication."

This study comes on the heels of another paper by National Jewish Health faculty, which showed that low levels of vitamin D in adult asthma patients are associated with lower lung function and reduced responsiveness to corticosteroids.

Severe asthma in early childhood may lead to premature loss of lung function

Children With Severe Asthma Experience Premature Loss of Lung Function During Adolescence, Study Finds

ScienceDaily (Jan. 20, 2011) — Severe asthma in early childhood may lead to premature loss of lung function during adolescence and more serious disease during adulthood, researchers at Emory University School of Medicine report. Early identification and treatment of children with severe asthma is important to help stem asthma progression.

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In an article available online in the January issue of the Journal of Allergy and Clinical Immunology, Anne M. Fitzpatrick, PhD, and W. Gerald Teague, MD, and colleagues report on their study of how airflow limitation changes throughout childhood and how this affects disease severity later in life. Fitzpatrick is an assistant professor of pediatrics in Emory University School of Medicine. Teague, who was formerly at Emory, currently is at the University of Virginia School of Medicine.

"Severe asthma in children is a challenging disorder," says Fitzpatrick. "It is important for physicians to identify those children with severe asthma who are at risk for lung function decline. With early identification, physicians can customize treatment plans and educate families on lifestyle changes that may help children with severe asthma breathe easier as they grow older."

Severe asthma in children is characterized by serious respiratory complications despite treatment with high doses of inhaled corticosteroids (ICS). Although there are similarities between children and adults with severe asthma, recent research has shown that the limitation of airflow is not as significant in children as in adults. This raises questions about the course of severe asthma in childhood and the critical developmental time frame during which loss of lung function occurs.

The authors used data from children with mild-to-moderate and severe asthma who were enrolled in a long-term National Heart, Lung, and Blood Institute Severe Asthma Research Program. The children were ages 8-11 years at the first evaluation and 11-14 years at the follow-up visit. Comparing measurements of symptoms, medication use and lung function, the researchers analyzed changes in the children's respiratory health over an average three-year period.

The authors found that children with severe asthma reported a higher frequency of daily symptoms and hospitalization during the previous year despite higher doses of ICS and controller medication, and that they had significantly lower lung function when compared to children with mild-to-moderate asthma. Additionally, they noted that daily asthma symptoms such as coughing and wheezing and sensitization to aeroallergens during the initial evaluation were strong predictors of declines in lung function of more than one percent per year.

The authors conclude that children with severe asthma have a premature loss of lung function during the adolescent years that is associated with an increased frequency of wheezing and asthma symptoms and greater allergic sensitization during childhood. Further studies are needed to determine whether the loss of lung function is due to a slower rate of lung growth or to progressive changes in the lung tissues, and to explore the mechanisms that control the responses of severely asthmatic children to ICS treatment.