COPD risk was 23% higher in people within the lowest quintile vs. the fourth quintile of 25(OH)D concentrations, according to research appearing in BMJ Open Respiratory Research.
While low vitamin D status has been linked to increased inflammatory diseases risk and to the regulation of pathogenic mechanisms in COPD, epidemiological evidence regarding the associations of 25(OH)D concentrations with COPD incidence and survival remains inconclusive, Zheng Zhu, MD, of Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, China, and colleagues wrote.
From UK Biobank data recorded from 403,648 participants (mean age 56.4 years; 54% women) who were free of COPD at baseline and had 25(OH)D measurements, researchers estimated hazard ratios and 95% confidence intervals for the associations of 25(OH)D concentrations with COPD risk and survival. After median follow-up of 12.3 years (ending Sept. 30, 2021), with 11,008 COPD cases recorded, beyond the COPD and mortality increase (HR, 1.23; 95% CI, 1.16-1.31) in the lowest quintile of 25(OH)D concentrations, risk for overall death was 38% higher, as well (HR, 1.38; 95% CI, 1.22-1.56). Serum concentrations were greater than 64.6 nmol/L in the highest (quintile 5) and less than 31.7 nmol/L in the lowest (quintile 1). Also, men and current smokers had higher COPD and mortality risk (P interaction for both: < .05).
While event rates tracked generally inversely with 25(OH)D concentrations, overall the event curves were non-linear. Dr Zhu and associates reported that the decreasing risk of COPD appeared to be lowest at 55 nmol/L of 25(OH)D within quintile 4 (51.8 to < 64.6 nmol/L). Furthermore, lower prediagnostic 25(OH)D concentrations were associated with a significant decrease in overall and COPD-specific survival.
Smoking is the most commonly encountered risk factor for COPD, the researchers noted, and their findings indicated that 25(OH)D concentrations were inversely associated with COPD risk in both smokers and never-smokers. In a fully adjusted model, compared with quintile 4, the quintile 1 increase in COPD risk was 25% in never-smokers and 23% in smokers.
“Our findings imply that vitamin D might play a role in progression of COPD,” the authors stated. They added, “Whether lower concentrations of 25(OH)D are causal or contributory to COPD risk may spur future long-duration and large-scale RCTs.”
“Vitamin D has an important function in the immune system and lower serum levels have been implicated in a variety of inflammatory diseases,” commented associate professor of medicine Diego J. Maselli, MD, who is chief of the division of pulmonary diseases & critical care at UT Health San Antonio. “Patients with COPD often have lower levels of vitamin D compared to healthy individuals. COPD patients with low serum levels of vitamin D may have a higher risk of exacerbations and worse lung function.”
He added, “The research by Zhu and colleagues adds to the field of study and highlights the potential role of vitamin D in the pathophysiology of COPD. It is important to remember that these associations do not establish causality, as patients with chronic and debilitating diseases may have limited sunlight exposure, poor nutritional intake, and other behaviors that may affect vitamin D levels. There are mixed results in studies evaluating the role of supplementing vitamin D in COPD with regards to disease progression and exacerbation reduction. While there are some studies that report that supplementation of vitamin D can reduce COPD exacerbations, there is still a need for randomized controlled studies that explore if the supplementation of vitamin D can prevent the development of COPD, particularly in those who actively smoke. Yet, it is reasonable to evaluate the serum vitamin D levels in COPD patients who have had exacerbations and supplement when there is a severe deficiency.”
Given that the majority of participants in this study were from the United Kingdom, the researchers stated, a study limitation is that findings might not apply to other populations.
No disclosures were reported by Dr. Zhu or by Dr. Maselli.