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ORIGINAL ARTICLE
Relationship of vitamin D status with lung function and exercise capacity in COPD JI YE JUNG,1 YOUNG SAM KIM,1 SE KYU KIM,1 HA YAN KIM,2 YEON MOK OH,3 SANG MIN LEE,4 JOON BEOM SEO,4 SANG-DO LEE3 AND KOLD Study 1 Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Institute of Chest Diseases, Yonsei University College of Medicine, Seoul, Korea and 2Biostatistics Collaboration Unit, Yonsei University College of Medicine, Departments of 3Pulmonary and Critical Care Medicine and Clinical Research Center for Chronic Obstructive Airway Diseases and 4Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
ABSTRACT Background and 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 nondeficiency 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 Correspondence: Sang-Do Lee, Department of Pulmonary and Critical Care Medicine, and Clinical Research Center for Chronic Obstructive Airway Disease, Asan Medical Center, University of Ulsan College of Medicine, 88 Asanbyeongwon-gil, Songpa-gu, Seoul 138-736, Korea. Email: [email protected] Received 2 November 2014; invited to revise 24 November 2014; revised 28 January 2015; accepted 5 February 2015 (Associate Editor: Melissa Benton). Article first published online: 13 April 2015 © 2015 Asian Pacific Society of Respirology
SUMMARY AT A GLANCE A high prevalence of vitamin D deficiency was observed in Korean patients with COPD. A significant relationship between vitamin D deficiency and airflow limitation were demonstrated, while the exercise capacity tended to be decreased in the vitamin D deficiency group.
tended to be decreased in the vitamin D deficiency group. Key words: chronic obstructive pulmonary disease, exacerbation, lung function, exercise, vitamin D. Abbreviations: 6MW, 6-min walking; 25-OH-VitD3, 25-OH vitamin D3; BMI, body mass index; COPD, chronic obstructive pulmonary disease; CT, computed tomography; FEV1, force expiratory volume in 1 s; FVC, forced vital capacity; GEE, generalized estimating equations; GOLD, Global Initiative for Chronic Obstructive Lung Disease; LMM, linear mixed model; QOL, quality of life; OR, odds ratio; SGRQ, St. George’s Respiratory Questionnaire.
INTRODUCTION The relationship between vitamin D status and chronic obstructive pulmonary disease (COPD) has attracted attention in recent years. It has been recognized that COPD is a systemic disease with various closely related comorbidities such as coronary heart disease, cancer, inflammatory disease, osteoporosis and infection.1 All of these diseases are known to be associated with the vitamin D status. Vitamin D deficiency is a widespread problem among adults in the general population and specifically in patients with COPD.2–4 This interest began with an observational study in the United States that identified a relationship between lower vitamin D levels and reduced lung function.5 However, inconsistent associations have Respirology (2015) 20, 782–789 doi: 10.1111/resp.12538
Influence of vitamin D status in COPD
been reported between vitamin D levels and lung function/lung function decline.5–9 Additionally, several studies have examined the relationship between vitamin D levels and other clinical characteristics of COPD such as the exacerbation frequency, hypoxemia, comorbidities, respiratory symptoms, quality of life (QOL), functional capacity and mortality.8–17 Increasing but conflicting evidence has been published regarding the effects of vitamin D on various clinical parameters of COPD. Most previous studies had important weaknesses in common, namely their cross-sectional design and analysis of blood vitamin D levels at one time point, at the beginning of the study, with evaluation of serial clinical parameters.4,8,9,11,13,15,18–20 Therefore, they could not exclude the possibility that the blood vitamin D level might have changed after the baseline measurement. The purpose of this study was to evaluate the effect of the vitamin D status on several clinical parameters, such as lung function, exercise capacity, QOL, exacerbation and the emphysema index, in a Korean COPD cohort by repeated and simultaneous measurement of the vitamin D level and these clinical parameters.
METHODS Study subjects In total, 193 patients with COPD from the Korean Obstructive Lung Disease (KOLD) Cohort, in which patients with COPD or asthma are enrolled from pulmonary clinics in 17 hospitals in South Korea, were evaluated from June 2005 to 2011. The patients fulfilled the following criteria: post-bronchodilator ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) of 40 years of age, smoking history of ≥10 pack-years, and no or minimal abnormality on chest radiography. Airway obstruction is defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria as an FEV1/ FVC ratio of
ORIGINAL ARTICLE
Relationship of vitamin D status with lung function and exercise capacity in COPD JI YE JUNG,1 YOUNG SAM KIM,1 SE KYU KIM,1 HA YAN KIM,2 YEON MOK OH,3 SANG MIN LEE,4 JOON BEOM SEO,4 SANG-DO LEE3 AND KOLD Study 1 Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Institute of Chest Diseases, Yonsei University College of Medicine, Seoul, Korea and 2Biostatistics Collaboration Unit, Yonsei University College of Medicine, Departments of 3Pulmonary and Critical Care Medicine and Clinical Research Center for Chronic Obstructive Airway Diseases and 4Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
ABSTRACT Background and 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 nondeficiency 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 Correspondence: Sang-Do Lee, Department of Pulmonary and Critical Care Medicine, and Clinical Research Center for Chronic Obstructive Airway Disease, Asan Medical Center, University of Ulsan College of Medicine, 88 Asanbyeongwon-gil, Songpa-gu, Seoul 138-736, Korea. Email: [email protected] Received 2 November 2014; invited to revise 24 November 2014; revised 28 January 2015; accepted 5 February 2015 (Associate Editor: Melissa Benton). Article first published online: 13 April 2015 © 2015 Asian Pacific Society of Respirology
SUMMARY AT A GLANCE A high prevalence of vitamin D deficiency was observed in Korean patients with COPD. A significant relationship between vitamin D deficiency and airflow limitation were demonstrated, while the exercise capacity tended to be decreased in the vitamin D deficiency group.
tended to be decreased in the vitamin D deficiency group. Key words: chronic obstructive pulmonary disease, exacerbation, lung function, exercise, vitamin D. Abbreviations: 6MW, 6-min walking; 25-OH-VitD3, 25-OH vitamin D3; BMI, body mass index; COPD, chronic obstructive pulmonary disease; CT, computed tomography; FEV1, force expiratory volume in 1 s; FVC, forced vital capacity; GEE, generalized estimating equations; GOLD, Global Initiative for Chronic Obstructive Lung Disease; LMM, linear mixed model; QOL, quality of life; OR, odds ratio; SGRQ, St. George’s Respiratory Questionnaire.
INTRODUCTION The relationship between vitamin D status and chronic obstructive pulmonary disease (COPD) has attracted attention in recent years. It has been recognized that COPD is a systemic disease with various closely related comorbidities such as coronary heart disease, cancer, inflammatory disease, osteoporosis and infection.1 All of these diseases are known to be associated with the vitamin D status. Vitamin D deficiency is a widespread problem among adults in the general population and specifically in patients with COPD.2–4 This interest began with an observational study in the United States that identified a relationship between lower vitamin D levels and reduced lung function.5 However, inconsistent associations have Respirology (2015) 20, 782–789 doi: 10.1111/resp.12538
Influence of vitamin D status in COPD
been reported between vitamin D levels and lung function/lung function decline.5–9 Additionally, several studies have examined the relationship between vitamin D levels and other clinical characteristics of COPD such as the exacerbation frequency, hypoxemia, comorbidities, respiratory symptoms, quality of life (QOL), functional capacity and mortality.8–17 Increasing but conflicting evidence has been published regarding the effects of vitamin D on various clinical parameters of COPD. Most previous studies had important weaknesses in common, namely their cross-sectional design and analysis of blood vitamin D levels at one time point, at the beginning of the study, with evaluation of serial clinical parameters.4,8,9,11,13,15,18–20 Therefore, they could not exclude the possibility that the blood vitamin D level might have changed after the baseline measurement. The purpose of this study was to evaluate the effect of the vitamin D status on several clinical parameters, such as lung function, exercise capacity, QOL, exacerbation and the emphysema index, in a Korean COPD cohort by repeated and simultaneous measurement of the vitamin D level and these clinical parameters.
METHODS Study subjects In total, 193 patients with COPD from the Korean Obstructive Lung Disease (KOLD) Cohort, in which patients with COPD or asthma are enrolled from pulmonary clinics in 17 hospitals in South Korea, were evaluated from June 2005 to 2011. The patients fulfilled the following criteria: post-bronchodilator ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) of 40 years of age, smoking history of ≥10 pack-years, and no or minimal abnormality on chest radiography. Airway obstruction is defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria as an FEV1/ FVC ratio of
