Associations between 25-hydroxy-vitamin D levels, lung function, and exacerbation outcomes in COPD: An analysis of the SPIROMICS cohort.

Burkes RM, Ceppe AS, Doerschuk CM, Couper D, Hoffman EA, Comellas AP, Barr RG, Krishnan JA, Cooper C, Labaki WW, Ortega VE, Wells JM, Criner GJ, Woodruff PG, Bowler RP, Pirozzi CS, Hansel NN, Wise R, Brown TT, Drummond MB