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 (<20ng/ml versus ≥20ng/ml). Stratifying by age group (middle-age: 40-64 years old and older: >65 years old), multivariable modeling was performed to identify relationships between 25-OH-vitamin D levels and the COPD Assessment Test (CAT), the modified Medical Research Council score (mMRC), the St George's Respiratory Questionnaire (SGRQ) total and subdomain scores, the Veterans' Specific Activity Questionnaire, and the 6-minute walk test distance. Results: In the middle-aged group, each 5ng/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 the 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.