Chronic Obstructive Pulmonary Disease Is Associated with Low Levels of Vitamin D

Introduction: COPD patients may be at increased risk for vitamin D (25(OH)D) deficiency, but risk factors for deficiency among COPD patients have not been extensively reported. Methods: Serum 25(OH)D levels were measured by liquid chromatography double mass spectrometry in subjects aged 40–76 years from Western Norway, including 433 COPD patients (GOLD stage II-IV) and 325 controls. Levels <20 ng/mL defined deficiency. Season, sex, age, body mass index (BMI), smoking, GOLD stage, exacerbation frequency, arterial oxygen tension (PaO2), respiratory symptoms, depression (CES-D score≥16), comorbidities (Charlson score), treatment for osteoporosis, use of inhaled steroids, and total white blood count were examined for associations with 25(OH)D in both linear and logistic regression models. Results: COPD patients had an increased risk for vitamin D deficiency compared to controls after adjustment for seasonality, age, smoking and BMI. Variables associated with lower 25(OH)D levels in COPD patients were obesity ( = −6.63), current smoking ( = −4.02), GOLD stage III- IV ( = −4.71, = −5.64), and depression ( = −3.29). Summertime decreased the risk of vitamin D deficiency (OR = 0.22). Conclusion: COPD was associated with an increased risk of vitamin D deficiency, and important disease characteristics were significantly related to 25(OH)D levels

Coefficients from multiple linear regression and logistic regression models, showing the relationship between baseline predictors and serum levels of 25(OH)D in COPD patients.

*<p>For both the linear and logistic regression models a backward stepwise procedure was used with the following variables included at start: Age, sex, GOLD status, hypoxemia (resting PaO₂<8), dyspnea (grade III), inhaled steroids, ICS (yes or no), *body mass index (BMI), comorbidity (Charlsons score <2 or ≥2), total white blood count, treatment for osteoporosis (yes or no), depression (CES-D score≥16) and exacerbation frequency (≥2 last year; yes or no).</p>#<p>Season was defined as winter (December–March), spring (April–May), summer (June–September), and autumn (October–November).</p

Correlation analysis of continuous variables associated with baseline concentrations of serum 25(OH)D.

#<p>BMI: Body mass index.</p>§<p>PaO₂: Arterial oxygen tension.</p

Forced expiratory volume in 1 s (FEV₁) plotted as a function of serum 25(OH)D levels for COPD patients and controls.

<p>The Pearson coefficient (r) is calculated and given in the graph.</p

Serum levels of 25(OH)D in ng/mL, mean±sd, for different potential explanatory variables by subject category.

*<p>BMI: body mass index.</p>#<p>Exacerbations requiring either hospitalisation or treatment with oral antibiotics or oral steroids.</p>§<p>PaO₂: arterial oxygen tension.</p>**<p>Associations were tested with t-test and ANOVA.</p

Baseline characteristics of the study sample, presented as mean±sd for continuous and percentage for categorical variables.

§<p>BMI: body mass index.</p>*<p>FEV₁: Forced expiratory volume in 1 s.</p>##<p>Season was defined as winter (December-March), spring (April-May), summer (June-September), and autumn (October–November).</p>#<p>Exacerbations requiring either hospitalisation or treatment with oral antibiotics or oral steroids.</p>§§<p>PaO₂: arterial oxygen tension.</p>**<p>Associations were tested with t-test and Chi-square.</p