Are 25(OH) D concentrations associated with asthma control and pulmonary function test?

Background: The relationship between vitamin D and asthma is still under investigation. We aimed to evaluate the association between serum vitamin D levels and clinical characteristics of asthma, and the impact of vitamin D deficiency on the clinical manifestations, as them being the issues of debate. Methods: Patients who were admitted to the outpatient clinics of Chest Diseases Department of Akdeniz University Hospital between January 2014 and December 2014, have been diagnosed as asthma according to the GINA 2014 guidelines were included in this study. Subjects with COPD, bronchiectasis, pneumonia or tuberculosis were excluded. Asthma exacerbation was defined, according to the GINA guidelines, as episodes of progressive shortness of breath, cough, wheezing or chest tightness accompanied by PFT abnormalities such as decreased PEF or FEV1. Results: A total of 158 patients with mean age of 48.8 years were included in the study. Twenty-seven (17.08%) of the patients demonstrated sufficient vitamin D serum levels (i.e. ≥30 ng/mL), while the remaining 131 (82.92%) patients had vitamin D insufficiency (i.e. <30 ng/mL). When these two patient groups (vitamin D sufficient vs. insufficient) were compared with each other, the patients showing sufficient levels of vitamin D were found to reveal significantly higher FEV1 (L) and FVC (L) values. When the patients were grouped into 4 categories with regard to their serum vitamin D measurements, hospitalization numbers were found to significantly increase with decreasing vitamin D levels. Conclusion: Vitamin D deficiency was significantly associated with poorer pulmonary functions and higher hospitalization numbers.