Exercise-induced
dyspnea is common among adolescents and young adults and often originates from exercise-induced bronchoconstriction (EIB). Sometimes,
dyspnea corresponds to exercise-induced
laryngospasm (EILO), which is a paradoxical decrease in supraglottic/glottic area.
Vitamin D deficiency, which occurs frequently at northern latitudes, might favor
laryngospasm by impairing
calcium transport and slowing striate muscle relaxation. The aim of this study was to evaluate whether
vitamin D status has an influence on bronchial and laryngeal responses to exercise in young, healthy athletes. EIB and EILO were investigated during winter in 37 healthy competitive rowers (24 males; age range 13-25 years), using the eucapnic voluntary
hyperventilation test (EVH). EIB was diagnosed when forced expiratory volume in the first second decreased by 10%, EILO when maximum mid-inspiratory flow (MIF50) decreased by 20%. Most athletes (86.5%) had
vitamin D deficiency (below 30 ng/mL), 29 mild-moderate (78.4%) and 3 severe (8.1%). EVH showed EIB in 10 subjects (27%), EILO in 16 (43.2%), and combined EIB and EILO in 6 (16.2%). Athletes with EILO had lower
vitamin D (19.1 ng/mL vs. 27.0 ng/mL, p < 0.001) and higher
parathyroid hormone (30.5 pg/mL vs. 19.2 pg/mL, p = 0.006) levels. The degree of laryngoconstriction (post-EVH MIF50 as a percentage of pre-EVH MIF50) was related directly with
vitamin D levels (r = 0.51; p = 0.001) and inversely with
parathyroid hormone levels (r = -0.53; p = 0.001). We conclude that
vitamin D deficiency is common during winter in young athletes living above the 40th parallel north and favors
laryngospasm during exercise, probably by disturbing
calcium homeostasis. This effect may negatively influence athletic performance.