Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Estimate of white-coat effect and arterial stiffness Giovanni de Simone a , Giuseppe Schillaci b , Marcello Chinali a , Fabio Angeli b , Gian Paolo Reboldi c and Paolo Verdecchia c Objectives Blood pressure (BP) measured in the office is usually higher than the average ambulatory BP, a difference generally taken as an estimate of the white-coat effect. This study was designed to assess whether such a difference is associated with impairment of the conduit arterial system. Methods We calculated the difference between office and average daytime peak systolic blood pressure (DSBP) in 2778 hypertensive participants (1240 women) of the Progetto Ipertensione Umbria Monitoraggio Ambulatoriale cohort. Arterial stiffness was evaluated using an adjusted office pulse pressure to stroke volume ratio (P P /SV), measured at rest, which has previously been shown to predict cardiovascular outcome independent of echocardiographic left ventricular hypertrophy. Effective arterial elastance was also estimated. Results Across quintiles of P P /SV, significant linear, positive trends were found with age, the proportion of women, plasma glucose and triglyceride levels (0.05> P < 0.0001). Heart rate measured in the office increased mildly with quintiles of P P /SV (P <0.05). After adjusting for age, sex, body weight and office heart rate, DSBP progressively increased with increasing quintiles of P P /SV (P for trend < 0.0001), whereas stroke volume decreased, paralleling the increase in left ventricular relative wall thickness (both P <0.0001) and left ventricular mass index (P < 0.05). The significant increase in effective arterial elastance with quintiles of P P /SV was also independent of peak systolic BP, in addition to age, sex, heart rate and body weight. Conclusions The difference between office BP and ambulabory BP, an estimate of the white-coat effect, is strongly associated with increased arterial stiffness, evaluated by a two-element fluid system accumulator. J Hypertens 25:827–831 Q 2007 Lippincott Williams & Wilkins. Journal of Hypertension 2007, 25:827–831 Keywords: arterial hypertension, arterial stiffness, cardiovascular risk, ventricular hypertrophy, white-coat effect a Department of Clinical and Experimental Medicine, Federico II University Hospital, School of Medicine, Naples, b Department of Clinical and Experimental Medicine, University of Perugia, Perugia and c Department of Cardiovascular Disease, University of Perugia and Hospital R. Silvestrini, Perugia, Italy Correspondence and requests for reprints to Giovanni de Simone, MD, Department of Clinical and Experimental Medicine, Federico II University Hospital, via S. Pansini 5, 80131 Napoli, Italy Tel: +39 81 746 2013; fax: +39 81 546 6152; e-mail: simogi@unina.it Received 17 June 2006 Revised 24 November 2006 Accepted 30 November 2006 Introduction White-coat effect is a condition that includes different situations (white-coat effect, white-coat response, white-coat hypertension, etc.) characterized by a substantial difference between the blood pressure (BP) measured in the doctor’s office and the average BP recorded during the day [1–6]. As already high- lighted when the phenomenon was first described [1], the increase in office BP is also associated with an increase in heart rate, suggesting, among other mechanisms [7,8], an increased sympathetic drive [3,9], associated with an alert reaction [3,10]. Whatever the mechanism of the white-coat effect is, it is clear that some mismatch between flow output and resistance to flow is needed to elicit the white-coat response. Because the possible increase in flow output does not seem to be great enough to justify increased arterial pressure [11], even in those studies reporting it, the increase in systolic and pulse pressure measured in the white-coat response might well be caused by the combination of some minor alert response over a background of increased arterial stiffness. A number of studies in relatively small, selected, popu- lation samples in clinical settings, have reported some degree of impaired arterial compliance in clinical situations characterized by the white-coat effect [11–13], but this observation has not been unanimously confirmed [14]. We present results on the relationship between the white-coat effect and simple estimates of arterial stiffness, obtained in a very large, unselected population of untreated hyperten- sive individuals in the Progetto Ipertensione Umbria Monitoraggio Ambulatoriale (PIUMA) study, encompass- ing a wide age span, under the hypothesis that increased arterial stiffness might be the hallmark of the white-coat effect. Resting vascular load was also assessed. Methods The PIUMA study is a registry including 2778 hyperten- sive patients and a normotensive reference population (N ¼ 391), to evaluate the prognostic aspects of ambulat- ory BP monitoring in arterial hypertension. Details on the population and methods of this study have previously been reported [15–18]. For the present analysis, 2778 Original article 827 0263-6352 ß 2007 Lippincott Williams & Wilkins