The association between insulin sensitivity indices, ECG findings and mortality: a 40-year cohort study.

Background: Type 2 Diabetes is a major risk factor for cardiovascular (CV) mortality. Insulin resistance can be evaluated non-invasively by insulin sensitivity indices (ISI) such as the Mcauley index (MCAi), which is a function of the fasting insulin and triglycerides. Currently, the association between ISIs and ECG findings and all-cause and CV mortality is still not established in a large scale and heterogeneous population.
Method: In a prospective study of the Israel cohort on Glucose Intolerance, Obesity and Hypertension (GOH) second phase (1979-1982) 1830 men and women were followed until December-2016 for CV-mortality and December-2019 for all-cause mortality. ECGs were recorded and OGTTs performed during baseline. ISIs were categorized into quartiles and evaluated against ECG findings and all-cause and CV-mortality.
Results: Mean age at baseline was 52.0 ± 8.1 years, and 75 (15.2%) and 47 (25.3%) participants in the upper quartiles (Q _2-4 ) and the lower quartile (Q ₁ ) of the MCAi, presented with Ischemic changes on ECG respectively (p = 0.02). Multivariable analysis showed higher odds for ECG ischemic changes, for individuals in Q ₁ -MCAi (adjusted-OR = 1.7, 95% CI 1.02-2.8), compared with Q _2-4 -MCAi, which attenuated when excluding individuals with diabetes (adjusted-OR = 1.6, 95% CI 0.9-2.7, p = 0.09). Median follow up for all-cause and for cardiovascular mortality was 31 years and 37 years, respectively. Cox proportional-hazards regression showed an increased risk for all-cause mortality for individuals in Q ₁ -MCAi (HR = 1.2, 95% CI 1.02-1.3) as well as an increased risk for CV-mortality (HR = 1.4, 95%CI 1.1-1.8) compared with Q _2-4 -MCAi. Individuals in Q ₄ -Ln Homeostatic model assessment- Insulin Resistance (HOMA-IR) and Q ₁ - Quantitative Insulin Sensitivity Check Index (QUICKI) also presented with increased risk for all-cause-mortality (HR = 1.2, 95%CI 1.04-1.4; and HR = 1.2, 95% CI 1.04-1.4, respectively). Other ISIs did not show significant associations with CV-mortality.
Conclusion: Higher insulin-resistance, according to the MCAi, associated with ECG-changes, and with greater risk for all-cause and CV-mortality over a 40-year follow-up. The MCAi may be considered as an early predictive and prognostic biomarker for CV-morbidity and mortality in adults.