Possible interesting link between dipping status and morning surge for subclinical target organ damage in hypertension

Hypertension is highly prevalent worldwide and is a major cause of strokes (such as cerebral infarction, cerebral hemorrhage, and subarachnoid hemorrhage), heart diseases (such as coronary artery disease, cardiac hypertrophy, and heart failure), kidney diseases (such as nephrosclerosis and end-stage kidney disease), and macrovascular diseases (such as aortic dissection and peripheral artery disease). Therefore, the primary aim of the anti-hypertensive treatment is to present standard management strategies and evidence to all medical workers to provide appropriate treatment to patients with hypertension most frequently encountered by clinicians/practitioners in daily practice for the prevention of the onset/progression of hypertension complications in the brain/heart/kidney by blood pressure control.1 Concerning the method of BP measurements, accumulating evidence supports that the “out-of-clinic” BP, particularly the ambulatory BP profile, is important for a proper diagnosis of hypertension and estimation of BP control.2-4 Ambulatory BP monitoring allows the acquisition of critical information not only at the level of the 24-hour BP but also the BP variations that occur in the course of daily activities. Accumulated evidence has showed that ambulatory BP, another measure to estimate out-of-clinic BP, is a superior predictor of future cardiovascular events than clinic BP, and ambulatory nighttime BP is reportedly shown to be a superior predictor of future cardiovascular events than daytime BP.5 Home BP is also reportedly a better predictor of future cardiovascular events than clinic BP, and recent several home BP devices are capable of measuring automatically nocturnal BP have been developed.6-8 Particularly, in CKD patients the prevalence of nocturnal hypertension is high and increases with disease progression,9 and nocturnal hypertension is reportedly associated with the worsening of albuminuria10, 11 and the increased risks of further renal deterioration and future cardiovascular events.12 Thus, it should be important to measure nighttime BP level and to reduce nighttime BP, in order to inhibit renal deterioration and cardiovascular complication.13, 14 Furthermore, recent development in the devices for home BP measurement enables to store home BP readings in a cloud database and can permit not only participants but also experimenters to set the timing of nocturnal BP measurement via automatic information/communication technology (ICT), resulting in a precise schedule for the measurement of nocturnal home BP,8 as performed for glycemic control of diabetic patients.15 In addition, among the several parameters obtained by ambulatory BP monitoring, ambulatory BP variability reflects a complex phenomenon that involves both short- and long-lasting changes.16 The 24-hour BP varies not only because of a reduction in BP during nighttime sleep and an increase in the morning, but also because of sudden, quick, and short-term changes that occur both during the day and, to a lesser extent, at night. This phenomenon, ambulatory short-term BP variability, has been shown to depend on sympathetic vascular modulation and on atherosclerotic vascular changes.16 The ambulatory short-term BP variability is highlighted as an emerging parameter to assess “quality of BP control” by accumulated findings showing that hypertensive patients with similar 24-hour average BP values exhibited more severe organ damage when the short-term BP variability was greater.17-20 Thus, short-term BP variability is associated with cardiovascular injury and is one of important prognostic factors for CVD.21, 22 In this issue of Journal of Clinical Hypertension, Gong S et al aimed to examine the effect of nocturnal BP dipping status on the association between morning surge and subclinical target organ damage parameters including left-ventricular mass index, left-atrial dimension, and carotid intima-media thickness in 1252 untreated hypertensives participants in a cross-sectional design study.23 The authors showed that that nocturnal BP dipping status affects the association between morning surge and subclinical target organ damage, with a significant and positive association noted only in dippers (not in non-dippers or reverse-dippers) and independently of other BP parameters including 24-hour, daytime, nocturnal, and morning systolic blood pressure. Although the study design is essentially cross-sectional, but not longitudinal, the results are interesting and important for the researchers in the field of hypertension. Since the study design was not longitudinal, the authors cannot conclude any causal relationship from the findings of the present study and should tone down the conclusion about the relevant association. Nevertheless, as an attractive therapeutic target of interest for efficient treatment of hypertension, a possible interesting link between dipping status and morning surge for the pathogenesis of target organ damage in hypertension is proposed by the present study, and further clinical evidence are expected to seek the answer. This work was supported by grants from the Yokohama Foundation for Advancement of Medical Science, a Uehara Memorial Foundation grant, Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science, grants from Senshin Medical Research, the Banyu Life Science Foundation International, and the Salt Science Research Foundation (19C4), and a grant-in-aid from the Cardiovascular Research Fund, Tokyo, Japan. This research was also supported by the grant of Strategic Research Project of Yokohama City University, Japan Agency for Medical Research and Development (AMED), Yokohama City University research grant “KAMOME Project” and by TR-SPRINT (Translational Research program; Strategic PRomotion for practical application of INnovative Medical Technology) from AMED. The authors declared that they do not have anything to disclose regarding conflict of interest with respect to this manuscript.