Pericoronary Fat Attenuation Index Mediates the Link Between TyG Index and OSA Risk in Type 2 Diabetes

The comorbidity of type 2 diabetes mellitus (T2DM) and obstructive sleep apnea (OSA) represents a significant public health challenge. We quantified the mediating role of the coronary fat attenuation index (FAI) in the association between the triglyceride-glucose (TyG) index and OSA risk, characterizing its nonlinear dynamics.

In this retrospective cross-sectional study, we assessed OSA risk using the STOP-Bang questionnaire in 420 patients with T2DM undergoing coronary computed tomography angiography, classifying scores as low-risk (<3), intermediate-risk (3-4), or high-risk (≥5). We measured pericoronary adipose tissue (PCAT)-FAI in three major epicardial coronary arteries (the right coronary artery, the left anterior descending artery, and the left circumflex artery) and in the culprit vessels. The TyG index was calculated using: ln[fasting triglycerides (mg/dL) × fasting glucose (mg/dL)/2]. Statistical associations were evaluated using multivariable logistic regression, restricted cubic splines (RCS), and PROCESS macro-mediated analyses.

PCAT-FAI was significantly elevated in LAD, LCX, RCA, and culprit vessels in patients at intermediate or high OSA risk versus the low-risk group (all p < 0.05). After adjusting for age, sex, BMI, and medication, each 1-unit TyG increase conferred a 2.3-fold higher OSA risk (adjusted OR = 3.30, 95% CI [1.92, 5.67], p < 0.01). RCS revealed threshold effects: OSA risk increased nonlinearly when RCA-FAI exceeded -80 Hounsfield units (HU). RCA-FAI mediated 11.78% of the TyG index-OSA association (p = 0.03).

RCA-FAI partially mediates the impact of TyG on OSA severity through nonlinear pathways. These findings elucidate PCAT inflammation as a mechanistic link in T2DM-OSA comorbidity, supporting the use of RCA-FAI ≥ -80 HU screening for precision risk stratification.