C‐reactive protein–triglyceride glucose index and all‐cause mortality in postmenopausal women: A dual‐cohort study from the National Health and Nutrition Examination Survey and the China Health and Retirement Longitudinal Study

BACKGROUND: Insulin resistance and chronic inflammation each predict cardiovascular mortality, but they are usually studied separately. The C-reactive protein-triglyceride glucose index (CTI) combines both, yet its prognostic value in postmenopausal women, who experience concurrent rises in insulin resistance and inflammation, remains unknown. METHODS: We identified postmenopausal women from the National Health and Nutrition Examination Survey (NHANES) (1999-2018; n = 7007) and the China Health and Retirement Longitudinal Study (CHARLS) (2011; n = 4235). CTI = 0.412 × ln [hs-CRP (mg/L)] + ln[(fasting triglycerides × fasting glucose)/2]. The endpoint was all-cause mortality. We fitted Cox models, restricted cubic splines (RCS), and piecewise regression with likelihood ratio tests for threshold detection. RESULTS: Over a median 9.0 years (CHARLS) and 11.9 years (NHANES), 2940 deaths occurred (26.2%). Each 1-unit CTI increase carried a 28% higher mortality hazard after full adjustment (hazard ratio [HR] 1.28; 95% confidence interval [CI] 1.20-1.35; P < 0.001). The dose-response was nonlinear in NHANES (P < 0.001) but linear in CHARLS (P = 0.14). In NHANES, a threshold emerged at CTI = 5.43: above it, per-unit HR = 1.85 (95% CI 1.62-2.11); below, HR = 0.99 (95% CI 0.89-1.10; P = 0.87). The highest versus lowest tertile HRs were 1.51 (1.16-1.97) in CHARLS and 1.35 (1.22-1.49) in NHANES. Excluding baseline cancer cases did not change the results. CONCLUSION: Higher CTI predicts greater all-cause mortality in postmenopausal women. In the US cohort, risk rose sharply, above CTI = 5.43. The same trend in the Chinese cohort, although linear, suggests that CTI might be a useful risk marker across populations.