Associations of obstructive sleep apnea with truncal skeletal muscle mass and density

Sarcopenia has been associated with several conditions relevant to obstructive sleep apnea (OSA), such as aging and obesity, but a direct relationship between OSA and skeletal muscle alterations has not been identified. This study investigated associations between computed tomography (CT)-measured skeletal muscle indices and OSA severity. Analyzed were 334 patients who underwent polysomnography to diagnose OSA. Lumbar skeletal muscles were assessed with CT for the skeletal muscle mass index (SMI, cross-sectional area, normalized for height squared) and skeletal muscle density (SMD, fat infiltration). The apnea-hypopnea index (AHI) correlated positively with the SMI and negatively with SMD in both men and women. The AHI was weakly associated with SMI only in men (β = 0.11, P = 0.017) after adjustment for the body mass index (BMI) (BMI: β = 0.61, P < 0.001 in men, β = 0.65, P < 0.001 in women). The association of AHI and SMD was not significant after adjustment for BMI (BMI: β = -0.42, P < 0.001 in men, β = -0.64, P < 0.001 in women). Severity of OSA correlated with increases in skeletal muscle mass rather than muscle depletion and skeletal muscle adiposity. These associations were limited compared with the stronger associations between obesity and skeletal muscles.