What are the normal levels for ambulatory blood pressure measurement?

With acceptance of ambulatory blood pressure measurement as a useful technique in the management of hypertension, the question of what constitutes the upper limit of normality for 24 h blood pressures has been the subject of a number of reviews [1,2]. In fact, there has been remarkable similarity in a number of large population studies [3-10]. For example, taking the 95th percentile as the upper limit of the distribution of daytime blood pressure in various studies in different countries (Internation Database 141/88 mmHg [3,4], Ireland 138/89 mmHg [5], Belgium 137/88 mmHg [6], Japan 138/83 mmHg [7], Denmark 139/88 mmHg [8] and Italy 134/88 mmHg [9,10] gave variations of less than 7/6 mmHg for systolic and diastolic blood pressures, respectively, the average for all studies being 138/87 mmHg (for review, [6]). A review of the literature carried out independently by the American Society of Hypertension [11] and our group [1,2,6] produced an identical recommendation for the levels of daytime blood pressure that may be regarded as normal and abnormal, namely, that blood pressures above 140/90 mmHg are probably abnormal and that blood pressures below 135/85 mmHg are probably normal. Moreover, the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure in its recent communication takes blood pressures of awake subjects below 135/85 mmHg to be normal [12].