Background <p>Insulin resistance, represented by the triglyceride-glucose (TyG) index, shows interplay with visceral obesity and together promotes cardiovascular diseases and mortality. Recent NHANES data demonstrated that combining TyG with A Body Shape Index (ABSI) outperforms traditional TyG-derived indices in predicting cardiovascular mortality. However, validation in independent cohorts with extended follow-up is needed.</p> Methods <p>We analyzed 1,753 participants from Visit 7 of the Rancho Bernardo Study (1988–1992). TyG was calculated as ln[(triglycerides × glucose)/2], ABSI as WC/(BMI^2/3 × height^1/2), and TyG-ABSI as their product. Cox proportional hazards models assessed associations with all-cause mortality. Harrell’s C-index compared predictive performance, integrated discrimination improvement (IDI), and net reclassification improvement (NRI).</p> Results <p>During median follow-up of 26.3 years (maximum 31 years), 1,166 deaths occurred (66.5% mortality rate) with zero participants lost to follow-up. The highest TyG-ABSI quartile had significantly increased mortality versus the lowest (fully-adjusted HR = 1.68, 95% CI 1.40–2.02, <i>p</i> &lt; 0.001). TyG-ABSI demonstrated superior C-index (0.710) versus TyG alone (0.623, <i>p</i> &lt; 0.001), with significant IDI (0.032, <i>p</i> &lt; 0.001) and NRI (0.156, <i>p</i> &lt; 0.001). Restricted cubic spline analysis revealed a linear dose-response relationship (p for non-linearity = 0.184). Association was particularly strong in younger adults (&lt; 60 years: HR = 2.74, 95% CI 1.71–4.38, <i>p</i> &lt; 0.001; p-interaction &lt; 0.001).</p> Conclusions <p>TyG-ABSI demonstrated superior predictive value for all-cause mortality compared to TyG alone and other modified TyG indices. The particularly strong association in younger adults suggests TyG-ABSI may be especially valuable for early risk stratification.</p>