Association of lung function with visceral adiposity and skeletal muscle mass considering myosteatosis.

Background: Changes in body composition, including loss of muscle mass and obesity, adversely affect lung function.

Research question: What is the relationship between lung function, visceral adiposity, and skeletal muscle mass, considering myosteatosis measured using computed tomography (CT) scans in middle-aged Korean adults?

Study design and methods: We reviewed 15,827 participants (9237 men and 6590 women), with a mean age of 52.5 ± 8.3 years, who underwent comprehensive health examinations, including abdominal CT and spirometry. Selected CT scans were automatically segmented to quantify total abdominal muscle area (TAMA), visceral fat area (VFA) and subcutaneous fat area. Muscle quality was assessed by categorizing TAMA into three regions based on CT density: good-quality muscle (normal attenuation muscle area; NAMA), fatty muscle (low attenuation muscle area), and inter/intramuscular fat areas. Low lung function was defined as forced vital capacity (FVC %) and forced expiratory volume in one second (FEV₁ %) < 80 of predicted values. Standardized residuals for CT-derived measurements, adjusted for age and body mass index (BMI) using linear regression, were calculated and stratified into quartiles for lung function comparison. Multivariate logistic regression was employed to analyze associations between low lung function and variables.

Results: NAMA was positively correlated with FVC and FEV₁, whereas VFA was negatively correlated with both. In men, low FVC and FEV₁ were significantly associated with lower NAMA and higher VFA. Among women with obesity (BMI ≥ 25 kg/m²), low FVC and FEV₁ were significantly associated with higher VFA and lower NAMA (FVC only); among women without obesity, low FVC and FEV₁ were negatively associated with NAMA.

Interpretation: Lung function was significantly associated with visceral adiposity and skeletal muscle quality, which differed according to sex and BMI. Improving lung function may require tailored management, including reducing visceral fat and/or enhancing skeletal muscle quality based on CT-body composition analysis.