Vitamin D status in patients with chronic obstructive pulmonary disease at Chris Hani Baragwanath Hospital, Johannesburg, South Africa.

BACKGROUND

There has been a growing interest in nutritional/lifestyle factors, including vitamin D, that may affect chronic obstructive pulmonary disease (COPD). Most data are from Caucasian populations and temperate climates, with minimal African data.

OBJECTIVES

The primary objective was to determine the prevalence of vitamin D deficiency (25-hydroxyvitamin D (25(OH)D) ≤20 ng/mL) and insufficiency (25(OH)D 21 - 29 ng/mL) among patients with COPD. Secondary objectives were to investigate the association between vitamin D and demographic/lifestyle factors, lung function parameters, markers of COPD severity and corticosteroid use.

METHODS

A prospective, cross-sectional study of 76 patients with COPD was conducted at a tertiary hospital in Johannesburg, South Africa. Patients were interviewed regarding demographic/lifestyle factors, COPD severity markers and corticosteroid therapy. The most recent spirometry result was recorded. Blood samples were taken for measurement of calcium, alkaline phosphatase and vitamin D levels. Patients were stratified according to vitamin D status (deficiency and non-deficiency (25(OH)D >20 ng/mL, i.e. combined insufficiency and adequate levels)), and statistical analysis was performed to assess for associations.

RESULTS

The sample included 72% males and 63% black African patients. The prevalences of vitamin D deficiency and insufficiency were 48% (95% confidence interval (CI) 42 - 54) and 35% (95% CI 30 - 41), respectively. A Modified Medical Research Council (mMRC) dyspnoea score ≥2 was associated with a relative risk of 1.34 (95% CI 1.05 - 1.7) for vitamin D deficiency in univariate analysis. In multivariate regression analysis, only sunlight exposure (<1 hour/day) was an independent predictor of vitamin D deficiency (odds ratio 2.4; 95% CI 1.3 - 4.5).

CONCLUSION

There was a high prevalence of suboptimal vitamin D levels in this COPD sample population. A higher mMRC score was associated with an increased risk of vitamin D deficiency, while low sunlight exposure was the only independent predictor of vitamin D deficiency.

STUDY SYNOPSIS

This is the first study to provide prevalence data regarding vitamin D status in COPD patients in sub-Saharan Africa. The study highlights a relationship between vitamin D status and both symptom severity and sunlight exposure. Owing to the high prevalence of suboptimal vitamin D status among COPD patients, it may be useful to screen patients for vitamin D deficiency, especially those with a more severe phenotype. There may be scope for further studies to evaluate whether vitamin D supplementation corrects the deficiency and provides any clinical outcome benefit.