Higher serum 25-hydroxy(OH)-vitamin D levels are associated with fewer respiratory-specific symptoms in middle-aged patients with chronic obstructive pulmonary disease (COPD), according to study results published in Chronic Obstructive Pulmonary Diseases: Journal of the COPD Foundation.
The study included participants from the multicenter, observational SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study). Participants who were younger than 65 years of age (n=666) were classified as being middle-aged, while those who were at least 65 years of age were classified as older (n=955). The median ages in each group were 58 and 70 years, respectively.
Investigators modeled 25-OH-vitamin D levels continuously and categorically, comparing patients with serum levels of less than 20 ng/mL (deficient) and 20 ng/mL or more (sufficient). Multivariable modeling was used to identify associations between vitamin D levels and the COPD Assessment Test (CAT), modified Medical Research Council score (mMRC), St George Respiratory Questionnaire (SGRQ) total and subdomain scores, Veterans’ Specific Activity Questionnaire, and 6-minute walk test (6MWT) distance.
In the overall cohort, there was no association between higher vitamin D levels and favorable CAT scores, mMRC, SGRQ Symptoms subdomain scores, or 6MWT distance.
Middle-aged patients had significantly lower serum vitamin D levels (25.6 vs 30.8 ng/mL; P <.001). Each 5 ng/mL higher 25-OH-vitamin D level in patients classified as middle-aged was independently associated with a better CAT score (-0.35; 95% CI, -0.67 to -0.03; P =.03), total SGRQ (-0.91; 95% CI, -1.65 to -0.17; P =.02), as well as the SGRQ subdomains of symptoms (-1.07; 95% CI, -1.96 to -0.18; P =.02), impact (-0.77; 95% CI, -1.53 to -0.003; P =.049), and activity (-1.07; 95% CI, -1.96 to -0.18; P =.02).
In the older age group, vitamin D levels were only associated with the SGRQ Impact score (-0.42; 95% CI, -0.83 to -0.0001; P =.049). There was no significant association between levels of vitamin D and symptom scores in older patients. In the middle-age group, there were no associations between vitamin D levels and the mMRC, VSAQ, or 6MWT distance.
A limitation of the study included the cross-sectional nature of the examined associations, which precludes identifying causality between vitamin D and COPD symptoms.
The investigators concluded that their “findings highlight the need to explore mechanisms more robustly by which vitamin D may improve symptoms.”
Burkes RM, Couper DJ, Barjaktarevic IZ, et al. Age-dependent associations between 25-hydroxy vitamin D levels and COPD symptoms: analysis of SPIROMICS. Chronic Obstr Pulm Dis. Published online April 6, 2021. doi:10.15326/jcopdf.2020.0180