Background : Vitamin D deficiency is common in patients with COPD. It is associated with poor lung function and increased exacerbations. Several studies showed that inhaled or systemic glucocorticoids (GC) is significantly associated with vitamin D deficiency. This study aims to assess if 25-hydroxy vitamin D (25OHD) level is associated with GC intake in a tunisian population.

Methods : Prospective, comparative study including 2 groups of subjects (stable COPD : G1 ; healthy smokers : G2). Participants with a pathology or receiving treatment interfering with phosphocalcic metabolism were not included. mMRC scale was used to asses dyspnea perception. All participants underwent a whole body plethysmography. 25OHD was also mesured in all particiapnts. Vitamin D deficiency was defined as a 25OHD < 20 ng/mL.

Results : 88 subjects were included (G1 : n = 65 ; G2 : n = 23). The two groups were comparable according to age, gender and comorbidities. The risk of vitamin D deficiency was 4.2 times higher in G1 (95% CI [1.3-13]; p=0.01). In G1, vitamin D deficiency was associated with increased dyspnea (p<0.05), a  more severe airway obstruction (p<0.05) and a higher cumulative annual oral GC dose (p<0.05) but not to inhaled GC.

Conclusion : Vitamin D deficiency is very common in Tunisian patients with COPD ; it?s  signicantly associated with oral GC use. Its then mandatory to raise awareness among clinicians and patients about this topic.