Changes in muscle-to-fat ratio are associated with lung function decline and airflow obstruction in the general population.

Background: The long-term relationship between body composition and lung function has not yet been fully demonstrated. We investigated the longitudinal association between muscle-to-fat (MF) ratio and lung function among middle-aged general population.

Methods: Participants were enrolled from a community-based prospective cohort between 2005 and 2014. Lung function parameters (forced vital capacity [FVC], forced expiratory volume in 1 s [FEV], and FEV/FVC) and the MF ratio (total body muscle mass [kg]/fat mass [kg]) were assessed biannually via spirometry and bioelectrical impedance analysis, respectively.

Results: We followed up 4,712 participants (age 53.9 ± 7.9 years, men 45.8%) for 8 years. With an increase in MF ratio of 1, in men, the FVC increased by 43.9 mL, FEV by 37.6 mL, and FEV/FVC by 0.320%, while in non-smoking women, the FVC increased by 55.8 mL, FEV by 44.3 mL, and FEV/FVC by 0.265% (all P < 0.001). The MF ratio-decreased group showed further annual deterioration in lung function than the MF ratio-increased group (men: FVC - 44.1 mL vs. -28.4 mL, FEV -55.8 mL vs. -39.7 mL, FEV/FVC - 0.53% vs. -0.42%; non-smoking women: FVC - 34.2 mL vs. -30.3 mL, FEV -38.0 mL vs. -35.2 mL; all P < 0.001, except FEV in non-smoking women; P = 0.005). The odds ratio for the incidence of airflow obstruction according to the MF ratio was 0.77 (95% CI, 0.68-0.87) in men and 0.85 (95% CI, 0.74-0.97) in non-smoking women.

Conclusions: Long-term changes in the MF ratio are related to lung function deterioration and incidence of airflow obstruction in middle-aged general population.