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Effects of daily vitamin D supplementation on respiratory muscle strength and physical performance in vitamin D-deficient COPD patients: a pilot trial

Authors Rafiq R, Prins HJ, Boersma WG, Daniels JMA, den Heijer M, Lips P, de Jongh RT

Received 11 January 2017

Accepted for publication 3 April 2017

Published 28 August 2017 Volume 2017:12 Pages 2583—2592

DOI https://doi.org/10.2147/COPD.S132117

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Charles Downs

Peer reviewer comments 4

Editor who approved publication: Dr Richard Russell

Rachida Rafiq,1 Hendrik J Prins,2 Wim G Boersma,2 Johannes MA Daniels,3 Martin den Heijer,1 Paul Lips,1 Renate T de Jongh1

1Department of Internal Medicine and Endocrinology, VU University Medical Center, Amsterdam, 2Department of Pulmonary Diseases, Northwest Hospital group, Alkmaar, 3Department of Pulmonary Diseases, VU University Medical Center, Amsterdam, the Netherlands

Background: Although vitamin D is well known for its function in calcium homeostasis and bone mineralization, several studies have shown positive effects on muscle strength and physical function. In addition, vitamin D has been associated with pulmonary function and the incidence of airway infections. As vitamin D deficiency is highly prevalent in chronic obstructive pulmonary disease (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 are pulmonary function, handgrip strength, exacerbation rate, and quality of life.
Methods: We performed a randomized, double-blind, placebo-controlled pilot trial. Participants were randomly allocated to receive 1,200 IU vitamin D3 per day (n=24) or placebo (n=26) during 6 months. Study visits were conducted at baseline, and at 3 and 6 months after randomization. During the visits, blood was collected, respiratory muscle strength was measured (maximum inspiratory and expiratory pressure), physical performance and 6-minute walking tests were performed, and handgrip strength and pulmonary function were assessed. In addition, participants kept a diary card in which they registered respiratory symptoms.
Results: At baseline, the mean (standard deviation [SD]) serum 25-hydroxyvitamin D (25(OH)D) concentration (nmol/L) was 42.3 (15.2) in the vitamin D group and 40.6 (17.0) in the placebo group. Participants with vitamin D supplementation had a larger increase in serum 25(OH)D compared to the placebo group after 6 months (mean difference (SD): +52.8 (29.8) vs +12.3 (25.1), P<0.001). Primary outcomes, respiratory muscle strength and physical performance, did not differ between the groups after 6 months. In addition, no differences were found in the 6-minute walking test results, handgrip strength, pulmonary function, exacerbation rate, or quality of life.
Conclusion: Vitamin D supplementation did not affect (respiratory) muscle strength or physical performance in this pilot trial in vitamin D-deficient COPD patients.

Keywords: chronic obstructive pulmonary disease, vitamin D, physical performance, muscle strength, pulmonary function

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