According to the findings of a relatively small, single-centre study published in the Annals of Internal Medicine, high-dose vitamin D supplementation does not reduce exacerbation rates in patients with moderate-severe COPD.

According to the authors, research has shown that low serum 25-hydroxyvitamin D (25-[OH]D) levels are associated with impaired FEV1, and that vitamin D deficiency may be seen in up to 60-75% of patients with COPD.  It is unknown if this is a consequence of COPD or whether it may causally contribute to disease pathogenesis.  The current study sought to determine whether long-term, high-dose vitamin D supplementation has any beneficial effects for patients with COPD prone to exacerbations.

The single-centre study randomised 182 adults aged over 50 years with moderate to very severe COPD, an FEV1 of <80% predicted and a history of recent exacerbations to double-blind treatment with vitamin D supplements (100,000 IU; n=91) or placebo (n=91) every four weeks for one year.  The primary outcome was time to first exacerbation; secondary outcomes included exacerbation rate, time to first hospitalisation, time to second exacerbation, FEV1, quality of life, and death.

Although mean serum 25-(OH)D levels increased in the vitamin D group compared with the placebo group (mean between-group difference of 30 ng/mL; P<0.001), there was no statistically significant difference between the groups in median time to first exacerbation (84 days [IQR 29-200 days] for vitamin D versus 56 days [IQR 21-200 days] for placebo; hazard ratio [HR] 1.1; 95% CI 0.82 to 1.56; P=0.41).  There were also no significant differences in the secondary endpoints studied.  Although a reduction in exacerbation rate was seen in the subgroup of patients with severe vitamin D deficiency at baseline (serum 25-[OH]D levels <10 ng/mL), this was a post-hoc analysis and involved only a small number of patients (n=30).

The authors suggest that further studies focusing on patients with severe vitamin D deficiency are warranted, and suggest that intervention during earlier stages of COPD when patients receive fewer medications may be more effective.  They comment that more studies in other chronic diseases are required to further explore the safety and potential efficacy of such higher doses of vitamin D beyond bone health, particularly in those who are vitamin D-deficient with immune-related conditions.