The large prospective cohort study, involving 973 North American patients, reports that no association was found between baseline vitamin D levels and the subsequent risk of developing severe or acute aggravations of COPD symptoms – concluding that baseline 25(OH)D levels “are not predictive of subsequent risk of developing acute exacerbations of COPD (AECOPD).”
Writing in the American Journal of Respiratory and Critical Care Medicine, the American research team noted that the data from their randomized, controlled trial found no relationship between baseline Vitamin D levels and time to first AECOPD or between vitamin D levels and AECOPD exacerbation rates – adding that the notion that vitamin D supplementation might reduce the risk of acute aggravations in COPD patients “is not supported by our data.”
"Contrary to what we expected, baseline vitamin D levels were not related to the risk of subsequent AECOPDs in this large group of COPD patients at high risk of AECOPD," said research leader Dr Ken Kunisaki, of the Minneapolis Veterans Affairs Medical Center.
"Vitamin D supplementation is unlikely to have an effect on AECOPD risk in these patients," he argued.
Vitamin D for COPD
Kunisaki and his colleagues explained that vitamin D insufficiency and deficiency “are highly prevalent in COPD patients,” with the lowest of the sunshine vitamin associated with the most severe airflow obstruction.
“Patients with severe COPD are [also] at the highest risk for exacerbations, so we hypothesized that low vitamin D levels might increase the risk of AECOPDs," said Kunisaki.
Indeed, many previously reported studies have suggested that low vitamin D status may influence lung functioning – with a recent study in mice suggesting that deficiency of the vitamin can lead to functional and structural abnormalities in during lung development.
Whilst further studies have also suggested that high dose supplements of the vitamin could increase the exercise capacity and strength of respiratory muscles in people with COPD.
In the current study, the authors reported that during a one year of follow-up, participants experienced a total of 1415 AECOPDs. They said that of 973 subjects followed 37% (360) remained AECOPD-free, whilst 29% (278) had one AECOPD, 14% (133) had two AECOPDs, and 21% (202) suffered three or more AECOPDs.
In the primary analysis of their results, Kunisaki and his team said that vitamin D levels had been found to have no relationship to time to first AECOPD, whilst secondary analyses found that vitamin D levels were also unrelated to annualised rates of AECOPD.
They did, however, add that participants with severe vitamin D deficiency had a higher mean rate of AECOPDs, but added that this difference was not found to be statistically significant.
Kunisaki added that the negative results of the research are “in contrast with earlier studies in which lower vitamin D levels were associated with higher rates of respiratory infections in adults and more frequent asthma exacerbations in children."
The team said that while vitamin D “may have an effect on respiratory exacerbation risk in patients with asthma, complex effects in COPD such as bacterial colonization, airway inflammation, systemic inflammation, oxidative stress, and impaired mucociliary clearance may have stronger effects on AECOPD risk than any effects of 25(OH)D [levels].”
Source: American Journal of Respiratory and Critical Care Medicine
Published online ahead of print.
“Vitamin D levels and risk of acute exacerbations of chronic obstructive pulmonary disease: a prospective cohort study”
Authors: K.M. Kunisaki, D.E. Niewoehner, J.E. Connett