Blood Pressure Levels and Triglyceride–Glucose Index: A Cross-Sectional Study from a Nationwide Screening in Mongolia

<b>Background</b>: The triglyceride-glucose (TyG) index has emerged as a reliable surrogate marker of insulin resistance. This study aimed to investigate the association between blood pressure (BP) levels and the TyG index and to assess whether even modest elevations in BP were associated with higher TyG index values. <b>Methods</b>: A cross-sectional analysis was conducted using data from 120,264 participants who underwent nationwide health screening in Mongolia between 2023 and 2024. BP was categorized into five stages. The TyG index was calculated based on fasting triglyceride and glucose levels. <b>Results</b>: The mean TyG index increased progressively with advancing hypertension stages (<i>p</i> for trend <0.001). Multivariate analysis showed that even elevated BP was independently associated with a higher TyG index (adjusted OR 1.108, 95% CI 1.039-1.183; <i>p</i> = 0.002), with the association strengthening across hypertension stage 1 (adjusted OR 1.238, 95% CI 1.200-1.277), stage 2 (adjusted OR 1.516, 95% CI 1.463-1.572), and hypertensive crisis (adjusted OR 1.575, 95% CI 1.350-1.836) (all <i>p</i> < 0.001). Central obesity further amplified the association between hypertension stage and TyG index levels. Among participants without central obesity, the TyG index increased from 8.086 (95% CI: 8.079-8.093) in the normal BP group to 8.449 (8.362-8.536) in the hypertensive crisis group. Similarly, among those with central obesity, the TyG index rose from 8.345 (8.336-8.354) in the normal group to 8.732 (8.685-8.778) in the hypertensive crisis group. <b>Conclusions</b>: This study demonstrates that the TyG index rises consistently with increasing BP stages, even at early elevations, suggesting that insulin resistance may begin at modest blood pressure increases.