Severe and uncontrolled adult asthma is associated with vitamin D insufficiency and deficiency

Background: Vitamin D has effects on the innate and adaptive immune system. In asthmatic children low vitamin D levels are associated with poor asthma control, reduced lung function, increased medication intake, and exacerbations. Little is known about vitamin D in adult asthma patients or its association with asthma severity and control. Methods: Clinical parameters of asthma control and 25-hydroxyvitamin D (25(OH)D) serum concentrations were evaluated in 280 adult asthma patients (mean +/- SD: 45.0 +/- 13.8 yrs., 40% male, FEV1 74.9 +/- 23.4%, 55% severe, 51% uncontrolled). Results: 25(OH)D concentrations in adult asthmatics were low (25.6 +/- 11.8 ng/ml) and vitamin D insufficiency or deficiency (vitamin D <30 ng/ml) was common (67%). 25(OH)D levels were related to asthma severity (intermittent: 31.1 +/- 13.0 ng/ml, mild: 27.3 +/- 11.9 ng/ml, moderate: 26.5 +/- 12.0 ng/ml, severe: 24.0 +/- 11.8 ng/ml, p = 0.046) and control (controlled: 29.5 +/- 12.5 ng/ml, partly controlled 25.9 +/- 10.8 ng/ml, uncontrolled: 24.2 +/- 11.8 ng/ml, p = 0.030). The frequency of vitamin D insufficiency or deficiency was significantly higher in patients with severe or uncontrolled asthma and was associated with a lower FEV1 (vitamin D <30 vs. >= 30 ng/ml 2.3 +/- 0.9 L vs. 2.7 +/- 1.0 L, p = 0.006), higher levels of exhaled NO (45 +/- 46 ppb vs. 31 +/- 37 ppb, p = 0.023), a higher BMI (28.3 +/- 6.2 vs. 25.1 +/- 3.9, p < 0.001), and sputum eosinophilia (5.1 +/- 11.8% vs. 0.5 +/- 1.0%, p = 0.005). The use of oral corticosteroids or sputum eosinophilia was associated with a 20% or 40% higher risk of vitamin D insufficiency or deficiency. Conclusions: 25(OH)D levels below 30 ng/ml are common in adult asthma and most pronounced in patients with severe and/or uncontrolled asthma, supporting the hypothesis that improving suboptimal vitamin D status might be effective in prevention and treatment of asthma.