A vitamin D deficiency in people with chronic obstructive pulmonary disease (COPD) is associated with a decline in lung function, and with increased odds of acute exacerbations, a large-scale analysis found.
These results identify vitamin D as a potential biomarker for COPD-related outcomes, the researchers suggest.
The study, “Associations Among 25-Hydroxyvitamin D Levels, Lung Function, and Exacerbation Outcomes in COPD,” was published in the journal CHEST.
People with a vitamin D deficiency have lower lung function and increased chronic bronchitis. That has been reported in the National Health and Nutrition Examination Study (NHANES), a program under the umbrella of the Centers for Disease Control that is designed to assess the health and nutritional status of adults and children in the U.S.
Some studies have implicated a vitamin D deficiency as a risk factor for airflow restriction and physical function in people with COPD; however, the outcomes of studies measuring lung function decline over time have been mixed.
While clinical trials failed to show an ease of COPD symptoms following supplements of vitamin D, a more detailed analysis of the connection between vitamin D deficiency and COPD may help inform clinicians.
Thus, researchers at the University of North Carolina, in collaboration with investigators at multiple research facilities across the U.S., conducted a more comprehensive study to determine if there is a connection between vitamin D and lung function and acute exacerbations in people with COPD.
SPIROMICS participants included current and former smokers, ages 40-80, with and without chronic airflow obstructions. Demographic data, medical and smoking history, and serum samples were collected. Lung function, as measured by FEV-1 — forced expiratory volume, or the amount of air breathed out in one second — was tested at the study’s enrollment (baseline) and at a one-year follow-up visit.
The analysis assessed 1,609 participants, with an average age of 65. In total, 42% were female, and 14% were Black. Severe COPD was present in 34% of the participants, and 31% reported one or more acute exacerbations in the year before the study.
Vitamin D was measured based on the levels of serum 25-OH-vitamin D, a circulating form of vitamin D and a standard indicator of vitamin D levels. Those with vitamin D levels below 20 nanograms/mL (ng/mL) were considered vitamin D deficient.
The results showed that 21% of the individuals had vitamin D deficiency, and that the condition was more prevalent in younger people (62 vs. 66 years), current smokers, and Blacks.
This deficiency was found to be associated with a 4.11% decrease in %-predicted FEV1 (percentage of normal) at baseline, meaning worse lung function.
For each 10 ng/mL decrease in 25-OH-vitamin D levels at the study’s start, there was a 1.04 %-predicted decrease in FEV1. Vitamin D deficiency also was associated with a significantly more substantial decline in the rate of %-predicted FEV1 over the first year of follow-up.
The odds of experiencing an exacerbation in the year before enrollment were higher among those who were vitamin D deficient. A 10 ng/ml decrease in 25-OH-vitamin D was linked to a 14% increase in the odds of an exacerbation, and a 17% increase for severe exacerbation.
After adjustments for parameters such as smoking status, age, sex, and race, the odds of exacerbation in the year before enrollment were 32% higher in vitamin D-deficient patients. Indeed, every 10 ng/ml decrease in 25-OH-vitamin D levels was associated with an 11% increase in exacerbation risk.
No link was found between vitamin D levels and severe exacerbation after one year.
CT scan analysis was done to further compare patients who were vitamin D deficient with those who were not. That analysis found no differences in the number of individuals with emphysema, functional small airways disease, or airway wall thickness.
Overall, the team said they observed vitamin D deficiency in approximately one in five participants with COPD in the group analyzed. “Active smokers, blacks, and younger participants were more likely to have” the condition, the researchers wrote.
“Lower 25-OH-vitamin D levels are independently associated with lower baseline lung function as well as greater odds of an [exacerbation] in the year before enrollment,” they added.
The team suggested that 25-OH-vitamin D levels could be “a potentially useful marker” of adverse COPD-related outcomes.
“Our analysis highlights the need for further studies of COPD populations to identify who may benefit from 25-OH-vitamin D supplementation,” they concluded.
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