The impact of plasma 25-hydroxyvitamin d on lung function in patients with cystic fibrosis

Causer, A. J., Saynor, Z. L., Arregui-Fresneda, I., Connett, G., Allenby, M. I., Daniels, T., Carroll, M. P., Urquhart, D. S. and Revuelta Iniesta, R. (2020) The impact of plasma 25-hydroxyvitamin d on lung function in patients with cystic fibrosis. Clinical Nutrition ESPEN, 40, 537-538. (doi:10.1016/j.clnesp.2020.09.394).

Abstract

Rationale: 25-hydroxyvitamin D (25OHD) exerts immunomodulatory effects on lung health1. Therefore, this study investigated if 25OHD is a predictor of lung function in people with Cystic Fibrosis (pwCF).Methods: A multi-centre retrospective review of pwCF (>5 years old) attending either the Royal Hospital for Sick Children (Edinburgh) or the Wessex CF-Unit (University Hospital Southampton) was performed between Jan 2018-Oct 2019. Demographic and clinical data were collected. Body Mass Index (BMI) Kg/m2 for adults and UK-WHO BMI z-scores for children were calculated. Plasma 25OHD measured closest in time to spirometry (Forced expiratory volume FEV1%) was recorded. 25OHD status was defined using NICE guidelines (50 nmol/L: sufficiency). Hierarchical multiple-regression analysis with FEV1% predicted as the primary outcome and other factors known to contribute to lung function (25OHD, age, VO2max, BMI and BMI z score) was performed.Results: Ninety pwCF [mean±SD age: 19.13±8.56 years, 54 (60%) children, 48 (53%) males and 88 (98%) Caucasian] were included. The prevalence of vitamin D deficiency and insufficiency was 4 (5%) and 13 (15%) respectively. Of these, 17 (100%) had vitamin D supplementation [median (IQR) 2000 (1500-2500)] IU/day prescribed. In total 84 (93%) pwCF were receiving vitamin D 1400 (800-1780) IU/day. There was no correlation between vitamin D intake and 25OHD. The median (IQR) length of time between blood and lung function tests was 66 (21-335) days. PwCF 25OHD was 67.99±26.86 nmol/L, VO2max 88.81±22.05, BMI 22.53±3.40 Kg/m2 and BMI z-score -0.05±1.08. Plasma 25OHD was not a significant predictor of lung function [R2=0.06; p=0.4; 95% CI (-0.09 to 0.19)].Conclusion: This study does not support the hypothesis that plasma 25OHD modulates lung function in pwCF. However, mechanistic and high-quality prospective studies in which lung tests are performed within the 25OHD half-life period (±15 days) are warranted.

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Contributors

Author: Z. L. Saynor

Author: G. Connett

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