Association between airflow limitation severity and reduced bone mineral density in Japanese men

Introduction: This study aimed to assess the association between airflow limitation (AL) severity and reduced bone mineral density (BMD) in Japanese men. Subjects and methods: This cross-sectional study included 290 subjects aged over 40 years (mean age 72.0, SD 11.6), who underwent a comprehensive health examination, including spirometry and measurement of BMD at the left femoral neck using dual-energy X-ray absorptiometry (DXA), between 2016 and 2017 at Japanese Red Cross Kumamoto Health Care Center. AL was defined as forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) of <0.7. Reversibility tests were not performed in this study. The criteria used for the AL staging were developed according to the Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) guidelines. The subjects were divided into the following three groups: a control group (normal pulmonary function), GOLD Stage I group (mild AL), and GOLD Stage II-IV group (moderate-to-very severe AL). BMD was classified based on the young adult mean (YAM) as normal (88.6% <= YAM [-1 SD <=]), osteopenia (70% <YAM <88.6% [<- 1 SD and > -2.5 SD]), or osteoporosis (YAM <= 70% [<= -2.5 SD]). Reduced BMD was defined as osteopenia, osteoporosis, or medication used for osteoporosis. Logistic regression analysis was used to assess the association between AL severity and the reduced BMD. Results: The prevalence of reduced BMD in subjects with moderate-to-severe AL (76.2%) was significantly higher than in those without AL (47.9%) (p=0.030). In logistic regression models adjusted for age, body mass index, pack-years, physical activity, and alcohol drinking, the risk of reduced BMD (odds ratio: 3.87; 95% confidence interval: 1.20-12.49; p=0.024) was significantly higher in subjects with moderate-to-severe AL than in those with normal pulmonary function. Conclusion: Present results suggest that reduced BMD is associated with AL severity in Japanese men.