KEYSTONE, COLO. — Low vitamin D levels in adults with asthma are associated with impaired lung function, increased airway hyperresponsiveness, and diminished in vitro response to glucocorticoids, according to a cross-sectional study.
The inference from this study is that vitamin D deficiency—a common finding in adults with asthma—may be one of the mechanisms underlying suboptimal clinical response to inhaled corticosteroids. This raises the testable hypothesis that vitamin D supplementation may improve asthma severity and treatment response, Dr. E. Rand Sutherland said at a meeting on allergy and respiratory diseases.
In light of the intriguing findings, a multicenter prospective clinical trial of vitamin D supplementation in asthma is being organized to see whether it improves asthma control. Results are probably 4 years away, said Dr. Sutherland, who is chief of the division of pulmonary and critical care medicine at National Jewish Health, Denver.
“I don't know that we have actionable data here in terms of what to do with asthmatics, but there is probably very little harm in giving 1,000-4,000 IU/day of cholecalciferol. If you're up against the wall in terms of what to do with a patient, this is one thing that's cheap, relatively easy, and may not be harmful,” he said in response to an audience question.
The cross-sectional study included 54 nonsmoking adults with persistent asthma. Their mean serum vitamin D concentration was 28 ng/mL; most experts consider levels below 30 ng/mL insufficient, he noted at the meeting, sponsored by the National Jewish Medical and Research Center.
The higher a participant's serum vitamin D concentration, the greater the lung function. In a multivariate regression analysis, there was a 22.7-mL increase in forced expiratory volume in 1 second (FEV1) for each 1-ng/mL increase in vitamin D (Am. J. Respir. Crit. Care Med. 2010;181:699-704).
Airway hyperresponsiveness was also more pronounced in participants with reduced vitamin D levels. These patients required a 1.03-mg/mL provocative concentration of methacholine to induce a 20% fall in FEV1, whereas 1.92 mg/mL was required in participants who had a serum vitamin D level of 30 ng/mL or more.
“We feel pretty good about these data as a potential biologic underpinning to some of the population data that suggested higher vitamin D concentrations are a biomarker of steroid responsiveness,” the pulmonologist observed.
Disclosures: The study was supported by the National Institutes of Health. Dr. Sutherland disclosed that he serves on advisory boards for Dey and GlaxoSmithKline and as a consultant to Schering-Plough.
There was a 22.7-mL increase in FEV1 for each 1-ng/mL increase in vitamin D.
Source DR. SUTHERLAND