Vitamin D status is associated with muscle strength and quality of life in patients with COPD: a seasonal prospective observation study
Received 28 February 2018
Accepted for publication 2 June 2018
Published 28 August 2018 Volume 2018:13 Pages 2613—2622
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 2
Editor who approved publication: Dr Richard Russell
Emma L Carson,1 L Kirsty Pourshahidi,1 Sharon M Madigan,2 Francina R Baldrick,1 Martin G Kelly,3 Eamon Laird,4 Martin Healy,5 JJ Strain,1 Maria S Mulhern1
1Nutrition Innovation Centre for Food and Health (NICHE), School of Biomedical Sciences, University of Ulster, Coleraine, Co. Londonderry, UK; 2Respiratory Dietitian, Pulmonary Rehabilitation Team, Belfast Health and Social Care Trust, Belfast, UK; 3Respiratory Team, Altnagelvin Hospital, Western Health and Social Care Trust, Londonderry, UK; 4School of Medicine, Trinity College, Dublin, Ireland; 5Department of Biochemistry, Central Pathology Laboratory, St James Hospital, Dublin, Ireland
Background: Owing to hospitalization, reduced functional capacity and consequently, less sunlight exposure, suboptimal vitamin D status (25-hydroxyvitamin D [25(OH)D]<50 nmol/L) is prevalent among COPD patients.
Objective: This study aimed to investigate seasonal changes in vitamin D status and any associated changes in fat-free mass (FFM), muscle strength and quality of life (QoL) in COPD patients.
Patients and methods: COPD patients living in Northern Ireland (n=51) completed study visits at the end of winter (March/April) and at the end of summer (September/October), corresponding to the nadir and peak of vitamin D status, respectively. At both time points, serum concentration of 25(OH)D was quantified by liquid chromatography-tandem mass spectrometry, FFM (kg) was measured using bioelectrical impedance and muscle strength (kg) was measured using handgrip dynamometry. QoL was assessed using the validated St George’s Respiratory Questionnaire.
Results: Mean±SD 25(OH)D concentration was significantly higher at the end of summer compared to the end of winter (52.5±30.5 nmol/L vs 33.7±28.4 nmol/L, P<0.001); and housebound patients had significantly lower 25(OH)D concentration compared to nonhousebound patients at the end of summer (42.9±4.2 vs 57.2±9.9 nmol/L; P<0.001). Muscle strength (at both time points) and QoL (end of summer only) were positively predicted by 25(OH)D concentration, independent of age, sex and smoking status.
Conclusion: This study highlights the need for health policies to include a recommendation for year-round vitamin D supplementation in housebound COPD patients, and wintertime supplementation in nonhousebound patients, to maintain optimal 25(OH)D concentrations to protect musculoskeletal health. Furthermore, an optimal vitamin D status may have potential benefits for QoL in these patients.
Keywords: vitamin D, COPD, muscle strength, quality of life, seasonal, 25(OH)D
This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution - Non Commercial (unported, v3.0) License. By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms.Download Article [PDF] View Full Text [HTML][Machine readable]