Age-Dependent Associations Between 25-Hydroxy Vitamin D Levels and COPD Symptoms: Analysis of SPIROMICS.

Introduction Age and vitamin D levels may affect symptom burden in chronic obstructive pulmonary disease (COPD). We used the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) to determine independent associations between vitamin D levels and COPD symptoms in different age strata. Methods Serum 25-hydroxy(OH)-vitamin D levels were modeled continuously and categorically ( 65 years old), multivariable modeling was performed to identify relationships between 25-OH-vitamin D levels and COPD Assessment Test (CAT), modified Medical Research Council score (mMRC), St. George Respiratory Questionnaire (SGRQ) total and subdomain scores, Veterans' Specific Activity Questionnaire, and six-minute walk test distance. Results In the middle-aged group, each 5 ng/ml higher 25-OH-vitamin D level was independently associated with more favorable CAT score [-0.35 (-0.67 to -0.03), P=0.03], total SGRQ [-0.91 (-1.65 to -0.17); P=0.02], and the SGRQ subdomains [Symptoms:-1.07 (-1.96 to -0.18), P=0.02; Impact: -0.77 (-1.53 to -0.003), P=0.049; Activity: -1.07 (-1.96 to -0.18), P=0.02]. These associations persisted after addition of comorbidity score, reported vitamin D supplementation, outdoor time, or season of blood draw to models. No associations were observed between 25-OH-vitamin D levels and symptom scores in the older age group. Discussion When controlled for clinically relevant covariates, higher 25-OH-vitamin D levels are associated with more favorable respiratory-specific symptoms and quality-of-life assessments in middle-age but not older COPD individuals. Study of the role of vitamin D supplementation in the symptom burden of younger COPD patients is needed.