Background: Intervention studies with vitamin D in asthma are inconclusive for several reasons, such as inadequate dosing or duration of supplementation or uncontrolled baseline vitamin D status. Our aim was to evaluate the benefit of long term vitamin D add-on in asthmatic patients with actual vitamin D deficiency, that is a serum 25-hydroxy vitamin D (25-OHD ) below 20 ng/mL.
Methods: Serum 25-OHD, asthma exacerbations, spirometry and inhaled corticosteroids (CS) dose were evaluated in a cohort of 119 asthmatic patients. Patients with deficiency were evaluated again after one year vitamin supplementation.
Results: 25-OHD was low in 111 patients and was negatively related to exacerbations (p < 0.001), inhaled CS dose (p = 0.008) and asthma severity (p = 0.001). Deficiency was found in 90 patients, 55 of whom took the supplement regularly for one year, while 24 discontinued the study and 11 were not adherent. Patients with vitamin D deficiency after 12 months supplementation showed significant decrease of exacerbations (from 2.6 ± 1.2 to 1.6 ± 1.1, p < 0.001), circulating eosinophils (from 395 ± 330 to 272 ± 212 10⁶/L, p < 0.001), and need of oral CS courses (from 35 to 20, p = 0.007) and improvement of airway obstruction.
Conclusions: Asthma exacerbations are favored by vitamin D deficiency and decrease after long-term vitamin D replacement. Patients who are vitamin D deficient benefit from vitamin D supplementation.
Keywords: airway obstruction; asthma exacerbations; vitamin D deficiency; vitamin D supplementation.