Vitamin D deficiency on lung function and emphysema in smoker

Objective Vitamin D deficiency (VDD) has been associated with lower lung function and faster lung function decline in smokers. Design We investigated the association of vitamin D on lung function and emphysema in smokers. Methods Subjects over 50 years-old were 2162 smokers who received lung health screening on health promotion center in 2012. We collected and analyzed spirometry, chest CT, 25 hydroxy vitamin D (25(OH)D), and clinical data. According to the presence of obstruction (FEV 1 /FVC <0.7) on spirometry and centrilobular emphysema on CT, subjects were divided to emphysema, obstruction, coexistent or control group. VDD was defined as serum 25(OH)D level <20 ng/ml. Results Among the participants, 128 (5.9%) subjects were allocated to emphysema, 246 (11.4%) obstruction, 93 (4.3%) coexistent group, and 1695 (78.4%) control and 53.7% were VDD, and mean 25(OH)D was 20.6±7.8 ng/ml. Coexistent group was older, and had more current heavy smokers, lower 25(OH)D (18.5±6.9 ng/ml), and higher proportion of VDD (61.3% vs 53.3%) than other groups. Emphysema group was younger (59.2 ±6.2 vs. 61.4±7.0 years-old, p=0.002) and had more current smokers than obstruction group (56.3% vs. 37.4%, p<0.001), while showing no differences in vitamin D and VDD between two groups. FEV 1 /FVC ratio was markedly different among 4 groups (78.5±4.6, 75.7±4.3, 64.3±4.9, and 60.2±8.9; control, emphysema, obstruction, and coexistent group, respectively, p<0.001). Conclusions There were no differences in vitamin D and VDD among emphysema, obstruction, and control groups. Coexistent emphysema and obstruction had lower vitamin D level and lower lung function. Further study will be needed to elucidate whether VDD precedes obstruction and emphysema or vice versa.