The Triglyceride–Glucose Index as a Measure of Insulin Resistance, Mediated the Relationship Between Air Pollution and Hypertension in Middle-aged and Older Adults

Abstract Background Previous studies have identified links between air pollution, insulin resistance (IR), and hypertension risk, but the mediating role of IR in the relationships between air pollution exposure and hypertension remains unexplored. Methods This national cross-sectional study included 10 405 middle-aged and older adults from 120 Chinese cities. Long-term air pollution exposure was estimated using 3-year average levels of 6 air pollutants (particulate matter with a diameter ≤ 2.5 μm [PM2.5] or ≤ 10 μm [PM10], nitrogen dioxide [NO2), sulfur dioxide [SO2], carbon monoxide [CO], and ozone [O3]). The triglyceride–glucose (TyG) index was used to assess IR. Generalized linear models were used to examine associations between air pollution, the TyG index, and hypertension risk. Mediation effect models were employed to evaluate the mediating role of the TyG index in the relationships between air pollution and hypertension. Results For each interquartile range increase in PM2.5, PM10, SO2, NO2, CO, and O3, we observed corresponding increases of 0.017, 0.019, 0.020, 0.027, 0.027, 0.013 in TyG index, and the odds ratio of 1.232, 1.269, 1.297, 1.323, 1.268, and 1.080 for hypertension, respectively. Mediation effect models revealed that the TyG index contributed 9.94%, 9.83%, 10.16%, 11.41%, 14.17%, and 21.89% mediating roles in the negative impact of PM2.5, PM10, SO2, NO2, CO, and O3 on hypertension risks, respectively. Conclusion Air pollution exposure was associated with increased IR and hypertension risk, with IR playing a significant mediating role. This study highlighted that IR could serve as a key biological mechanism linking air pollution to hypertension risk.