Low concentrations of serum 25-hydroxyvitamin D associated with increased risk for chronic bronchitis among US adults

Increasing evidence suggests that vitamin D benefits both innate and adaptive immunity, thereby eliciting an anti-inflammatory effect and reducing the risk of infectious disease. The present study examined the association between serum 25-hydroxyvitamin D (25(OH)D) levels and the risk of chronic bronchitis among US adults. We analysed data from 6872 US adults aged >= 20 years who participated in the 2003-6 National Health and Nutrition Examination Survey. Prevalence and OR with 95% CI of having self-reported chronic bronchitis were estimated by quintiles of 25(OH)D or vitamin D-deficiency status after adjustment for potential confounders. The results showed that the adjusted prevalence of chronic bronchitis ranged from 2.4 (95% CI 1.4, 3.3)% among adults in the highest quintile of 25(OH)D (>= 30 ng/ml) to 4.1 (95% CI 2.5, 5.6)% among adults in the lowest quintile (<15 ng/ml; P for trend<0.01). The adjusted OR for chronic bronchitis was 1.85 (95% CI 1.06, 3.24) in adults with <15 ng/ml 25(OH)D and 1.77 (95% CI 1.19, 2.65) in those with 15 to <20 ng/ml 25(OH)D compared with adults with >= 30 ng/ml 25(OH)D. Additionally, the adjusted OR for chronic bronchitis was 1.52 (95% CI 1.03, 2.26) among adults with vitamin D deficiency (<20 ng/ml 25(OH)D) compared with those with >= 20 ng/ml 25(OH)D. For every 1 ng/ml increase in 25(OH)D, the likelihood of having chronic bronchitis fell by 2.6% (P=0.016). In conclusion, low serum 25(OH)D levels are associated with the increased risk of chronic bronchitis among US adults. The present results provide support for continuing research on the role of vitamin D in lung diseases.