ARTERIAL STIFFNESS IS A DETERMINANT OF THE WHITE-COAT EFFECT IN YOUNG SUBJECTS IN THE INITIAL STAGES OF HYPERTENSION

Abstract

Objective: The white-coat effect (WCE) evaluated from the difference between office and ambulatory blood pressure (BP) is often pronounced in young hypertensive subjects chiefly in people with isolated systolic hypertension (ISHY). The WCE in this setting is considered to merely reflect the alarm reaction to doctor's visit and to be a benign phenomenon. However, the WCE might be amplified in subjects with stiffer arteries. The aim of this study was to investigate whether the WCE in the young is influenced by individual vascular characteristics and whether this putative association may differ according to hypertension subtype. Design and method: We examined 371 young-to middle age participants (mean age 31.1±8.7 years, 74.7% males). BP phenotypes were identified using ambulatory BP with a 24-hour BP cut-off of 130/80 mmHg. ISHY was present in 24.2 % of participants, isolated diastolic hypertension in 20.0%, systolic-diastolic hypertension in 30.1%, and normotension in 25.7%. Vascular stiffness was assessed by radial-carotid pulse wave velocity (PWV) and vascular compliance by radial tonometry. 24-hour urinary catecholamines were measured with HPLC in 101 participants. The association of WCE with arterial functional indexes was assessed with multivariable linear regression analysis controlling for ambulatory BP. Improvement in the models was expressed by the difference in the Akaike index(↗ AIC) Results: In the whole group, PWV was a significant predictors of the WCE with a ↗AIC of 9.9 (p = 0.001). In addition, a negative association was found between the WCE and large artery (p = 0.001) or small artery (p = 0.002) compliance. Twenty-four-hour urinary epinephrine and nor-epinephrine were totally unrelated to WCE. PWV was a significant predictor of the WCE also among the participants with ISHY with a ↗AIC of 8.2 (p = 0.002). This association was not present in the participants with isolated diastolic hypertension (p = 0.15) or systolic-diastolic hypertension (p = 0.28). Conclusions: These data indicate that arterial stiffness rather than sympatho-adrenergic activity is an important determinant of the surrogate measure of the WCE in young subjects in the initial stage of hypertension. This association was confirmed in the subgroup of participants with ISHY suggesting that in some individuals ISHY may not be a benign condition.