Relationship between skeletal muscle mass and lung function in Korean adults without clinically apparent lung disease

Previous studies have demonstrated that low skeletal muscle mass is related to decreased lung function in patients with chronic obstructive pulmonary disease. However, there is little information about the relationship between skeletal muscle mass and lung function in asymptomatic adults without clinically apparent lung disease. This was a cross-sectional study of 240,562 Korean adults without known lung disease. All subjects underwent both pulmonary function test (PFT) and bioelectrical impedance analysis in the health checkup program at Kangbuk Samsung Hospital. Skeletal muscle mass index (SMI) was estimated as skeletal muscle mass/weight×100. We analyzed the relationship between SMI and PFT using multivariate logistic regression models. Of the 240,562 study subjects, values for forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and peak expiratory flow (PEF) were decreased across quartiles (Qs) of decreasing SMI. After adjustments for various confounders including demographic and health behavior-related factors, odds ratios (ORs; 95% confidence interval) for subjects with FVC% <80% for Q1–Q3 compared with Q4 (reference) were 2.97 (2.74–3.17), 2.11 (1.99–2.27), and 1.66 (1.52–1.83), respectively. ORs for subjects with FEV1% <80% for Q1–Q3 compared with Q4 were 2.64 (2.43–2.83), 1.96 (1.83–2.09), and 1.51 (1.43–1.62), respectively. Lastly, OR for subjects with PEF% <80% for Q1–Q3 compared with Q4 were 1.73 (1.58–1.89), 1.35 (1.26–1.45), and 1.23 (1.15–1.30), individually. Subgroup analyses for gender and all age groups showed the associations of decreasing SMI Qs with lower FVC%, FEV1%, and PEF% remained significant. Decreased SMI was independently associated with decline in lung function in apparently healthy adults. This association was sustained in subgroup analyses by gender and all age groups.