Non-dipping in hypertension: still a challenging problem

Many individuals with elevated clinical blood pressure Many individuals with elevated clinical blood pressure do not develop hypertensive complications and a large number of subjects may be treated with little or no benefit to the individual . A body of evidence suggests that the average of the blood pressure readings recorded during 24 h with ambulatory monitoring is a more powerful predictor of outcome than clinical blood pressure and that it helps identify those subjects who really need antihypertensive treatment. Several attempts have been made to determine whether other parameters derived from 24-h blood pressure recording may add prognostic information to that provided by average ambulatory blood pressure. It is known that blood pressure varies markedly over a 24-h period but the prognostic significance of these changes is still a matter for dispute. In particular, much attention has been paid to the blood pressure changes associated with the sleep–wake cycle. Most individuals have a substantial fall in blood pressure when they sleep accompanied by a decrease in heart rate. These chnges are closely linked to the level of arousal. Following the introduction of ambulatory blood pressure monitoring, it appeared that some individuals have little or no fall in blood pressure when they sleep. This has led to classification of subjects into dippers and non-dippers. Whether this classification is associated with adverse outcome has been the subject of much debate . Although the evidence predominantly indicates the presence of a greater cardiovascular morbidity and mortality in non-dippers than dippers, the issue remains, at least in part, controversial due to a number of methodological problems. The main reasons for concern are the poor consistency shown by the diurnal blood pressure rhythm in reproducibility studies and the different criteria that have been used in the literature to define dipping/nondipping statu