BackgroundThe triglyceride glucose (TyG) index has been regarded as an effective proxy of Insulin resistance (IR). Studies on the TyG index, obesity and the risk of prehypertension (PHT) in elderly people are not apparent currently. The study sought to investigate the predictive value of TyG index and the associations with PHT risk and obesity.MethodsA community-based cross-sectional study was conducted in Bengbu City, Anhui province, China. Participants older than 65 years accepted questionnaire surveys, physical examinations and blood biochemistry tests. Based on the testing results, indicators including BMI (body mass index), WC (waist circumference), WHtR (waist-to-height-ratio), LAP(Lipid accumulation products) and TyG were calculated. Residents were classified into quartiles by their TyG indexes. Receiver operating characteristic curve (ROC) analysis was carried out to predict obesity indices for PHT. The three additive interaction indicators, RERI (relative excess risk due to interaction), AP (attributable proportion due to interaction) and S (synergy index) were used to assess the interaction impacts.ResultsTwo thousand six hundred sixty-six eligible elderly people were included in study and the prevalence of PHT was 71.04% (n= 1894). With increasing TyG index quartile, PHT became more prevalent. After adjusting for confounding factors, the prevalence of PHT risk with TyG levels in the fourth quartile (Q4, male: 2.83, 95%CI: 1.77–4.54; female: 2.75, 95%CI:1.91–3.97) was greater than that in the first quartile (Q1:ref). TyG index (AUC: 0.626, 95%CI: 0.602 to 0.650) was superior than BMI (AUC: 0.609, 95%CI: 0.584 to 0.633) in predicting PHT among females. Eventually, there were significant interactions of TyG index with obesity in males (General obesity: AP = 0.87, 95%CI: 0.72 to 1.02, S = 10.48, 95%CI: 3.43 to 31.97; Abdominal obesity: AP = 0.60,95%CI: 0.38 to 0.83, S = 3.53, 95%CI: 1.99 to 6.26) and females (General obesity: AP = 0.89, 95%CI: 0.79 to 0.98, S = 12.46, 95%CI: 5.61 to 27.69; Abdominal obesity: AP = 0.66, 95%CI: 0.51 to 0.82, S = 3.89, 95%CI:2.54 to 5.98).ConclusionTyG index and PHT risk are tightly correlated. The risk of chronic disease in the elderly can be decreased by early detection of PHT utilizing the TyG index. In this research, the TyG index was more predictable than other indicators of obesity.