title: Relationship of vitamin D status with lung function and exercise capacity in COPD.
abstract: OBJECTIVE
  The relationship between blood vitamin D level and clinical parameters in patients with chronic obstructive pulmonary disease (COPD) has been reported with conflicting results. We explored the effects of vitamin D on clinical characteristics of patients with COPD in Korea.
  
  
  METHODS
  The study population comprised 193 patients with COPD from Korean Obstructive Lung Disease Cohort. The plasma level of 25-OH vitamin D3 (25-OH-VitD3) was measured every year along with various clinical parameters such as lung function, 6-min walking (6MW) distance, quality of life, exacerbations and emphysema index. Generalized estimating equations and linear mixed model were used for statistical analysis.
  
  
  RESULTS
  Of the 193 patients, 12 (6.2%), 28 (14.5%) and 153 (79.3%) were categorized into normal, insufficiency and deficiency groups. Clustered analysis showed that the plasma 25-OH-VitD3 level was associated with the post-bronchodilator ratio of force expiratory volume in 1 s/forced vital capacity (FEV1 /FVC) (estimated = 0.001; P = 0.022). The vitamin D deficiency group showed lower FEV1 (estimated = -0.129, P = 0.043), FEV1 % predicted (estimated = -4.994, P = 0.029) and FEV1 /FVC ratio (estimated = -0.048, P = 0.001) than did the non-deficiency group. The 6MW distance tended to be shorter in deficiency group (estimated = -17.26, P = 0.069) than in non-deficiency group. Quality of life, exacerbation and emphysema index were not associated with plasma 25-OH-VitD3 level.
  
  
  CONCLUSIONS
  We demonstrated a high prevalence of vitamin D deficiency in Korean patients with COPD and a significant relationship between vitamin D deficiency and airflow limitation. The exercise capacity tended to be decreased in the vitamin D deficiency group.
authors: Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Institute of Chest Diseases, Yonsei University College of Medicine, Seoul, Korea.
authors: Ji Ye
authors: JY
authors: Jung
authors: Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Institute of Chest Diseases, Yonsei University College of Medicine, Seoul, Korea.
authors: Young Sam
authors: YS
authors: Kim
authors: Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Institute of Chest Diseases, Yonsei University College of Medicine, Seoul, Korea.
authors: Se Kyu
authors: SK
authors: Kim
authors: Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Korea.
authors: Ha Yan
authors: HY
authors: Kim
authors: Department of Pulmonary and Critical Care Medicine and Clinical Research Center for Chronic Obstructive Airway Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Yeon Mok
authors: YM
authors: Oh
authors: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Sang Min
authors: SM
authors: Lee
authors: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Joon Beom
authors: JB
authors: Seo
authors: Department of Pulmonary and Critical Care Medicine and Clinical Research Center for Chronic Obstructive Airway Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Sang-Do
authors: SD
authors: Lee
mesh_terms: D000368:Aged; D002112:Calcifediol / Q000097:blood / Q000172:deficiency; D015331:Cohort Studies; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology; D011656:Pulmonary Emphysema / Q000503:physiopathology; D011788:Quality of Life; D056910:Republic of Korea / Q000453:epidemiology; D012129:Respiratory Function Tests / Q000379:methods; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology
chemical_list: D002112:Calcifediol
keywords: chronic obstructive pulmonary disease; exacerbation; exercise; lung function; vitamin D