Background The ambulatory arterial stiffness index (AASI) is a new index that reflects the dynamic relation between diastolic and systolic blood pressure through the circadian blood pressure rhythm. It was the aim of this study to investigate the association between AASI, dipping status and pulse pressure as a classical indicator of arterial stiffness in normotensive and hypertensive subjects. Methods One hundred and twelve individuals were evaluated for a kidney donation to a relative at the University Hospital Essen, Germany. In this context routine 24-h ambulatory blood pressure measurements were performed. A nocturnal reduction in diastolic blood pressure of > 10% was defined as `dipping'. We determined the diurnal and nocturnal blood pressure and brachial pulse pressure values and computed AASI for each participant. Results AASI was a strong predictor for diastolic and systolic nocturnal blood pressure fall (r = -0.55 and -0.48, respectively; P < 0.001). Additionally, AASI predicted the status of ` dipping/nondipping'. ` Dippers' showed significantly lower AASI than ` nondippers' in both normotensive and hypertensive subjects. Dippers, but not nondippers, demonstrated an association between AASI and brachial pulse pressure. Discussion AASI is strongly correlated with nocturnal blood pressure fall and is increased in nondipping independent of blood pressure. The role of AASI as a potential marker for arterial stiffness depends, in this study, on the characterization of the dipping status.
