Dipping Deeper Into the Ambulatory Arterial Stiffness Index

Abstract

To the Editor: Methodologic and conceptual issues seriously weaken the conclusions of Schillaci et al1 on the ambulatory arterial stiffness index (AASI), as published in the May 2007 issue of Hypertension . Schillaci et al1 reported that, in 515 untreated patients, AASI depended on the nocturnal blood pressure fall. We confirmed this observation in our Flemish population study.2 The correlation coefficients were similar to those in the report by Schillaci et al1: −0.24 versus −0.28 for systolic blood pressure (2-sided P value computed by Fisher’s Z transformation, 0.42), and −0.39 versus −0.46 for diastolic blood pressure ( P =0.11). However, the ambulatory recording of 1 of the representative patients of Schillaci et al1 included ≈25 nighttime and ≈35 daytime readings. The night:day ratio of the number …