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.