Ambulatory Arterial Stiffness Index: Regression Method Comparison and Its Association With Pulse Pressure and Circadian Patterns

The Arterial Stiffness Index (AASI) is a calculation obtained through Ambulatory Blood Pressure Monitoring (ABPM), and is an indirect measure of the elastic properties of the arterial wall; but there is heterogeneity in its scope as a predictor of vascular wall health. A comparison is made between linear regression and exponential regression of the AASI, as well as an analysis of variance, according to circadian patterns and pulse pressure (PP) values. This work is an analytical observational study in 106 individuals, most of them women (63%) with a mean age of 53 ± 17.32 years. The coefficient of determination (r2) for the linear relationship was 0.53 ± 0.17, similar to the exponential relationship with an r² of 0.52 ± 0.17 (p = 0.7032). Patients with PP < 52 mmHg had an AASI of 0.3839 ± 0.1428 and for PP > 53 mmHg an AASI of 0.5330 ± 0.1108 (p < 0.0001). When comparing the AASI between Dipper vs. Riser circadian patterns, there was homoscedasticity (p = 0.3717); on the contrary, in the intergroup evaluation with Non-Dippers, heteroscedasticity was observed (Dipper vs. Non-Dipper; p = 0.0316 and Non-Dipper vs. Riser; p = 0.01978). This study concludes that the best determination of AASI is linear regression, robustly correlating with the values of PP > 53 mmHg and AASI > 0.5 (r = 0.9628). The behavior of the data in the Non-Dipper group is heterogeneous, probably due to their own physiological characteristics. In addition, AASI could be an indirect measure of arterial stiffness and be more directly associated with arterial elasticity and its deformation capacity.