Relationships Between Pulmonary Function and Composite Indices of Femoral Neck Strength in Korean Men (KNHANES IV)

Background: Despite the close relationship between osteoporosis and chronic pulmonary diseases, few studies have evaluated relationships between pulmonary functions and bone quality. We investigated associations between pulmonary function test results and femoral neck strength indices (SIs) in Korean men.

Methods: This population-based, cross-sectional study was conducted using data from the Korea National Health and Nutrition Examination Survey IV on 936 men aged ≥ 19 years. Pulmonary functions (forced vital capacity [FVC] and forced expiratory volume in one second [FEV₁]) were measured using a dry rolling seal spirometer. Femoral neck SIs, relative to load, were calculated by hip dual-energy X-ray absorptiometry for compression strength index (CSI), bending strength index (BSI), and impact strength index (ISI).

Results: The 443 (47.3%) of the 936 men were current smokers. FVC, FVC percentage with respect to the expected normal value, FEV₁, and FEV₁ percentage with respect to the expected normal value (FEV₁p) were positively associated with CSI and BSI after adjusting for confounders, including smoking history (β = 0.003-0.223, P = 0.005-0.036). FEV₁ and FEV₁p were positively associated with ISI (β = 0.000-0.014, P = 0.010-0.025). Of components of femoral neck SIs, bone mineral density was correlated with FEV₁ and FEV₁p (β = 0.001-0.037, P = 0.017-0.019). After adjusting for all confounders, all femoral neck SIs increased with FVC quintiles (P for trends = 0.001-0.012), and CSI and BSI increased with FEV₁ quintiles (P for trends = 0.034-0.043).

Conclusion: Reduced pulmonary function was correlated with reduced femoral neck strength, even after adjusting for smoking history in Korean men. Femoral neck SIs might be useful tools for evaluating bone health in men with reduced pulmonary function.