Kim C, Ko Y, Jung JY, et al. - Given that an increased risk of vitamin D deficiency is seen among patients with chronic obstructive pulmonary disease (COPD), and a correlation of vitamin D levels with lung function in COPD patients has been reported, so, researchers used the Korean Obstructive Lung Disease cohort to assess the influences of plasma 25-hydroxyvitamin D (25-OHD) level on the severity of emphysema among male COPD patients. This study included 151 male patients. Based on patients' baseline plasma 25-OHD level, four subgroups were defined: sufficiency (≥ 20 ng/ml), mild deficiency (15–20 ng/ml), moderate deficiency (10–15 ng/ml), and severe deficiency (< 10 ng/ml). According to the findings, the four subgroups demonstrated different computed tomography emphysema indices, and there exists an association of severe vitamin D deficiency with a rapid progression of emphysema in male COPD patients.