Associations of triglyceride–glucose–body mass Index and C-reactive protein with isolated nocturnal hypertension: evidence from a retrospective observational study

Objective Isolated nocturnal hypertension (INH) is an underrecognized blood pressure (BP) phenotype that is associated with a greater burden of cardiovascular risk despite normal daytime BP values. Metabolic disturbances together with sustained low-level inflammatory activity have been implicated in circadian BP abnormalities; however, data regarding simple and widely available biomarkers for identifying INH remain limited. The aim of the present study was to explore the relationships between metabolic indices and inflammatory markers in the context of INH and to further evaluate their potential value in predicting this condition. Methods We conducted a retrospective observational analysis at a single institution, including individuals who were evaluated using 24-hour ambulatory blood pressure monitoring (ABPM) between March 2024 and March 2025. INH was defined by a mean daytime BP below 135/85 mmHg in the presence of a mean nighttime BP of at least 120/70 mmHg. Demographic characteristics, laboratory parameters, C-reactive protein (CRP) levels and several metabolic indices—namely the triglyceride–glucose (TyG) index, its body mass index–adjusted form (TyG-BMI), and the atherogenic index of plasma (AIP)—were included in the analysis. Independent determinants of INH were examined using logistic regression models, while diagnostic accuracy was evaluated through receiver operating characteristic (ROC) curve analysis. Results The study population consisted of 241 participants, including 137 individuals with INH and 104 normotensive controls. Compared with the control group, those with INH exhibited significantly elevated TyG index, TyG-BMI, AIP and CRP levels (all p < 0.001). In multivariate logistic regression analysis, TyG-BMI [odds ratio [OR] 1.030, 95% confidence interval [CI] 1.002–1.059; p = 0.034] and CRP (OR 3.878, 95% CI 2.609–5.763; p < 0.001) remained independently associated with INH. ROC analysis demonstrated moderate discriminatory ability for TyG-BMI [area under the curve (AUC) 0.696, p < 0.001] and high discriminatory performance for CRP (AUC 0.861, p < 0.001). Conclusion Metabolic dysregulation and systemic inflammation are strongly associated with INH. TyG-BMI and CRP, derived from routinely available clinical data, may act as practical markers to identify individuals at increased risk for this clinically important BP phenotype.