Vitamin D deficiency has been linked to many chronic medical conditions, including asthma and chronic obstructive pulmonary disease (COPD). In some cases, more severe vitamin D deficiency is associated with more severe chronic illness.
However, it's never been shown that vitamin D deficiency supplemenation improves or prevents illness; i.e., that vitamin D deficiency causes or exacerbates illness and that treating the deficiency helps treat the illness (with the possible exception of osteoporosis). Rather, vitamin D deficiency may just be a marker of chronic illness; levels may fall further as COPD or another chronic illness progresses. A recent prospective longitudinal study in people with COPD published in AJRCCM 2012 suggested vitamin D levels had no correlation with COPD exacerbations.
An Lehouck, Chantal Mathieu, and Wim Janssens set out to test the question of whether vitamin D supplementation would reduce COPD exacerbations, publishing their results of their randomized controlled trial in the January 17 Annals of Internal Medicine.
What They Did
At a single center in Leuven, Belgium, investigators randomized 182 patients with moderate-to-severe COPD and a history of recent exacerbations to receive high dose (100,000 IU q 4 weeks) vitamin D or placebo for 1 year. Primary outcome was time to first exacerbation, as reported by patients in symptom diaries with pre-specified definitions for exacerbations.
Patients did not have to have vitamin D deficiency at baseline to be eligible, but as it turned out, most had low vitamin D levels (mean level 20 ng/mL), below some labs' threshold for mild vitamin D deficiency.
What They Found
Median time to first exacerbation did not differ between groups. Nor did death, FEV1, exacerbation rates, hospitalization, or quality of life (prespecified secondary endpoints). The patients taking vitamin D did achieve substantially higher vitamin D levels, a relative 30 ng/mL increase.
In a post-hoc, non-pre-specified analysis of the 30 patients with the most severe vitamin D deficiency at baseline, a reduction in COPD exacerbations could be identified (rate ratio 0.57, p=0.04). Authors urge caution and say this finding needs to be shown prospectively before concluding anything.
Vitamin D levels also did not correlate with risk of COPD exacerbation in a prospective, longitudinal cohort study on Vitamin D and COPD published in AJRCCM in 2012.
Lehouck A et al. High Doses of Vitamin D to Reduce Exacerbations in Chronic Obstructive Pulmonary Disease. A Randomized Trial. Ann Intern Med 2012;156:105-114.