Association between the triglyceride–glucose index and pain prognosis after interventional treatment for herpes zoster-associated neuralgia

Background Pain outcomes after interventional treatment for herpes zoster-associated neuralgia (HZAN) vary substantially, and reliable prognostic markers remain limited. The triglyceride–glucose (TyG) index is a simple surrogate marker of insulin resistance, but its association with pain prognosis after interventional procedures for HZAN is unknown. Methods In this retrospective study, patients with HZAN who underwent interventional pain procedures were included. The TyG index was calculated from fasting triglyceride and glucose levels and analyzed as both a continuous variable and by quartiles. Poor pain prognosis at 3 months after discharge was defined using a composite outcome reflecting clinically meaningful pain persistence and impact. Multivariable logistic regression models with incremental adjustment were constructed. To explore potential dose–response associations, restricted cubic spline models were constructed. In addition, prespecified subgroup analyses were conducted to explore potential effect modification across clinical subgroups. Results Among 345 patients, 86 (24.9%) met the composite endpoint for poor pain prognosis. After adjustment for clinically relevant covariates, each one-unit increase in TyG was associated with greater odds of poor pain prognosis (adjusted odds ratio (OR) 1.99, 95% confidence interval (CI) [1.25–3.18]). The adjusted OR for the highest versus lowest TyG quartile was 2.62 (95% CI [1.19–5.77]). The sensitivity analysis using a numeric rating scale (NRS) ≥4 at 3 months as the sole outcome yielded a similar association (adjusted OR 1.87, 95% CI [1.15–3.05]). Restricted cubic spline analysis found no evidence of nonlinearity, and subgroup analyses provided no statistically significant evidence of effect modification. Conclusions The TyG index demonstrates an independent association with pain prognosis after interventional treatment for HZAN, with a linear dose–response relationship. These findings support further investigation of TyG as a metabolic marker associated with pain prognosis, but do not establish its value for individual risk prediction.