Relationship between pulmonary function and bone mineral density in the Korean National Health and Nutrition Examination Survey

Background/Aims: Osteoporosis is common in chronic obstructive pulmonary disease (COPD) patients. The relationship between osteoporosis and COPD has been primarily reported in patients with moderate to severe COPD, but there is no report in the general population. The aim of this study is to investigate the relationship between bone mineral density (BMD) and lung function in the general Korean population. Methods: This study was based on data acquired from the Fourth and Fifth Korea National Health and Nutrition Examination Surveys (KNHANES IV and V), conducted from 2008 to 2010. The study population included 4,501 subjects (aged${\geq}50$ years) who underwent both spirometry and BMD. The study populations were divided into two groups by sex to correct for the effects of gender on BMD. All female participants were postmenopausal women. Results: The BMD values of the femur neck, total femur, and L-spine tended to decrease with degree of airflow limitation in both genders. To correct confounding factors, data were analyzed and adjusted for age, body mass index, fat free mass index, body fat percentage, smoking amount, parathyroid hormone levels, daily calcium and phosphorus intake, and alkaline phosphatase (ALP) levels. While the BMD of the femur neck, total femur, and L-spine was reduced significantly as age and ALP increased, the correlation between airway obstruction and BMD of all regions disappeared in both genders. Conclusions: In the general population aged 50 years and older, diminution of BMD is not associated with airway obstruction. Further investigation along other factors is needed to determine the possible role of pulmonary function and BMD.