Endocrine Abstracts

Introduction: Although vitamin D is well known for its function in calcium homeostasis and bone mineralisation, several studies have shown an effect on physical function and muscle strength. Also, vitamin D has been associated with pulmonary function and the incidence of airway infections. As vitamin D deficiency is highly prevalent in COPD-patients, supplementation might have a beneficial effect in these patients.

Objective: To assess the effect of vitamin D supplementation on respiratory muscle strength and physical performance in vitamin D-deficient COPD-patients. Secondary outcomes were exacerbation rate, pulmonary function and quality of life.

Methods: We performed a randomised, double-blind, placebo-controlled pilot trial. Participants were randomly allocated to receive 1200 IU vitamin D3 per day (n=24) or a placebo (n=26) during 6 months. Study visits were conducted at baseline, at 3 and at 6 months after randomisation. During the visits blood was collected, respiratory muscle strength was measured (maximum inspiratory and expiratory pressure (kPa), MIP and MEP respectively), physical performance tests were performed (3-meter walking test, tandem test, chair-stands test and 6-minutes walking test) and pulmonary function was assessed. In addition, during the whole study period participants kept a diary card in which they registered respiratory symptoms.

Results: At baseline, both groups were deficient (mean serum 25-hydroxyvitamin D (25(OH)D) in nmol/L (S.D.): 42.3(15.2) and 40.6(17.0) in the vitamin D and placebo-group respectively). Participants with vitamin D supplementation had a significant increase in 25(OH)D compared to the placebo-group after 6 months (mean difference (S.D.): 52.8(29.8) vs. 12.3(25.1), P<0.001). Pulmonary muscle strength did not differ between the groups after 6 months (mean difference MIP(S.D.): −0.28(1.43) and 0.25(1.23), P=0.215; mean difference MEP(S.D.): 0.92(3.37) and 0.51(2.07), P=0.649). Also, no differences were found in physical performance, exacerbation rate, pulmonary function or quality of life.

Conclusion: Vitamin D supplementation did not affect respiratory muscle strength and physical performance in vitamin D-deficient COPD-patients.