Association of the single-point insulin sensitivity estimator with arterial stiffness: a cross-sectional analysis.

Background: Arterial stiffness is an early marker of vascular damage and cardiovascular risk. SPISE is a simple insulin-free surrogate of insulin sensitivity, but its association with arterial stiffness remains unclear. This study assessed the association between SPISE and brachial-ankle pulse wave velocity (baPWV) in Japanese adults. Methods: A cross-sectional dataset of 912 adults from a health screening program in Gifu, Japan, was analyzed. SPISE was evaluated in two ways, including per-unit variation and quartile grouping. The independent association of SPISE with baPWV was estimated using linear regression techniques. To further explore the pattern of association, spline-based modeling was introduced, and subgroup and sensitivity analyses were further conducted to assess the robustness of the findings. Results: Higher SPISE levels were significantly associated with lower baPWV. With all covariates taken into account, baPWV decreased by 8.48 cm/s for each 1-unit higher SPISE (β = -8.48, 95% CI: -16.00 to -0.96; P = 0.027). Relative to the lowest quartile, the highest SPISE quartile had significantly lower baPWV (β = -56.17, 95% CI: -101.49 to -10.85; P = 0.015), with a significant trend across quartiles (P for trend = 0.013). The association was generally linear and consistent across subgroups. Sensitivity analyses showed that the association was robust to lipid adjustment but attenuated and changed direction after further adjustment for SBP, DBP, and fasting plasma glucose. Conclusion: Higher SPISE was generally associated with lower baPWV in Japanese adults and may serve as an easily obtainable metabolic marker associated with arterial stiffness.