Associations between CT-based body composition parameters and glycemic control in adults with type 2 diabetes mellitus: a retrospective cohort study

Background Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and impaired insulin secretion, leading to persistent hyperglycemia and multisystem complications. Adipose tissue distribution – visceral, subcutaneous, and intermuscular – varies in metabolic and inflammatory activity, influencing insulin sensitivity and systemic glucose homeostasis. Skeletal muscle also plays a critical role in glucose disposal. This study aims to evaluate the associations between CT-derived body composition metrics and glycemic control in adults with T2DM and to explore inter-individual variations in fat and muscle distribution. Methods In this retrospective cohort study, 651 adults with T2DM underwent chest CT imaging. Body composition – including visceral, subcutaneous, intermuscular, and total adipose tissue areas, along with skeletal muscle area – was quantified at the T8 vertebral level. Glycemic control was assessed using HbA1c (>7% indicating suboptimal control). Multivariable logistic regression models were employed to evaluate associations between body composition metrics and glycemic status, with adjustment for cardiometabolic and lifestyle covariates. The correlation between body composition and HbA1c was analyzed using dose–response relationships and smooth curve fitting. Subgroup analysis was then performed based on gender, age, diabetes duration, hypertension, lifestyle (smoking and alcohol consumption), and lipid levels to evaluate differences in body composition among these groups. Results The PGCS group (HbA1c ≥ 7%, 81.72%) exhibited significantly higher VAT, SAT, IMAT, and TAT areas, alongside a lower SM area and density (all P < 0.01). In multivariable logistic regression analyses, participants were divided into quartiles (Q1–Q4) based on body composition metrics. Regression analyses revealed that increased adipose tissue areas across different regions and reduced skeletal muscle mass were independent risk factors for poor glycemic control (VAT area Q4: OR = 2.54, P < 0.01; SAT area Q4: OR = 3.33, P < 0.01; IMAT area Q4: OR = 2.32, P < 0.02; TAT area Q4: OR = 3.98, P < 0.01), with significant dose–response relationships observed for all compartments. Smooth curve fitting demonstrated linear or nonlinear associations of SM, SAT, IMAT, and TAT areas with HbA1c. Subgroup analyses indicated a significantly elevated risk of poor glycemic control associated with a low SM area in individuals with BMI < 24 kg/m2, non-hypertensive patients, non-smokers, those with triglycerides ≥1.7 mmol/L, and those with cholesterol <5.2 mmol/L. The associations for various adipose tissue depots with glycemic control exhibited heterogeneity across these subgroups. Conclusions Increased adipose tissue deposition across distinct anatomical depots and reduced skeletal muscle mass were independently associated with suboptimal glycemic control in T2DM patients, with the associations exhibiting linear or non-linear dose–response relationships. Subgroup analyses further indicated that a lower skeletal muscle area and higher adiposity were consistently associated with a significantly elevated risk of poor glycemic control across most subgroups.