December 8, 2011 (Cancun, Mexico) — Vitamin D deficiency is associated with exercise-induced paradoxical vocal cord dysfunction (VCD) in young athletes, according to research presented here at the World Allergy Organization XXII World Allergy Conference (WAC). The study was conducted during the winter in a town above 45 degrees latitude.
Exercise can be associated with exercise-induced bronchospasm (EIB) or laryngospasm, which can be mistaken for asthma. The researchers had previously demonstrated that vitamin D deficiency is associated with VCD during a hyperventilation test, especially in hypocapnic conditions.
In a population of 37 nonsmoking young athletes (24 males, 13 females; age, 13 to 25 years), the researchers investigated the prevalence of EIB and exercise-induced VCD during a hyperventilation test. They then related the findings to vitamin D levels.
The hyperventilation test included five 1-minute runs in isocapnic (breathing carbon dioxide–enriched air) or hypocapnic (breathing normal air) conditions. Each test was performed 1 week apart. Capnography was used to monitor exhaled carbon dioxide pressure. The researchers used a 10% decrease in forced expiratory volume in 1 second as a marker of EIB and a 25% reduction in mid-inspiratory flow (MIF50) as a marker for exercise-induced VCD.
Of the participants, 16 (43%) were atopic and 6 (16%) reported that they had previously been diagnosed with asthma. None used drugs or had had respiratory infections in the previous month, and all had normal results on lung function tests. In isocapnic conditions on hyperventilation testing, 10 participants experienced EIB and 12 experienced exercise-induced VCD. Under hypocapnic conditions, 8 participants experienced EIB and 15 had exercise-induced VCD.
Vitamin D deficiency (serum 25-hydroxycholecalciferol < 25 ng/mL) was recorded in 18 participants (49%). Athletes with exercise-induced VCD had significantly lower serum levels of vitamin D than those without it, in both isocapnic (19.1 ± 1.8 vs 25.7 ± 1.5 ng/mL; P = .013) and hypocapnic (20.2 ± 1.9 vs. 26.2 ± 1.8 ng/mL; P = .029) conditions.
The researchers also found an association between vitamin D levels and a decrease in MIF50 (as percentage of baseline) during the test (under isocapnic conditions: r = .41; P < .015; under hypocapnic conditions: r = .42; P = .017).
The researchers found no correlation between vitamin D and EIB.
“I think the role of vitamin D and other micronutrients [in respiratory problems] is still poorly understood, and for sure they have a role both in this particular syndrome, but also in airway inflammation and so also asthma. I think it’s an interesting field to be expanded,” Enrico Heffler, MD, PhD, from the University of Torino, Italy, who presented the research at a poster session here, told Medscape Medical News.
Dr. Heffler also related a previous case study of a patient with severe vitamin D deficiency who experienced VCD and bronchospasm; symptoms and lung function were significantly improved after vitamin D supplementation.
“This study is fascinating because it links vitamin D deficiency to something new. [The researchers] need to do a double-blind placebo-controlled trial in these individuals,” Glenis Scadding, MD, a consultant allergist and rhinologist at the Royal National Throat, Nose and Ear Hospital, London, United Kingdom, who attended the session, told Medscape Medical News.