Prior studies and health surveys have shown that vitamin D deficiency is highly prevalent in the general US population and occurs in over 60% of patients with severe COPD. Previous epidemiological studies have shown that vitamin D deficiency is associated with increased frequency of respiratory infections, not only in COPD populations but in the general population as well, possibly due to the role of vitamin D in innate and adaptive immune regulation.
In a recently published study, severe vitamin D deficiency was associated with more frequent exacerbations of COPD and hospitalizations for COPD. This was a retrospective analysis of 97 COPD patients from Italy.
This study demonstrated an association but not a causal link. It is unknown whether vitamin D supplementation will decrease or prevent acute exacerbations of COPD or reduce the need for COPD hospitalizations and further studies on this issue are needed.