Blood pressure (BP) is characterized by marked short-term fluctuations occurring within a 24 h period (beat-to-beat, minute-to-minute, hour-to-hour, and day-to-night changes) and also by long-term fluctuations occurring over more-prolonged periods of time (days, weeks, months, seasons, and even years). Rather than representing 'background noise' or a randomly occurring phenomenon, these variations have been shown to be the result of complex interactions between extrinsic environmental and behavioural factors and intrinsic cardiovascular regulatory mechanisms. Although the adverse cardiovascular consequences of hypertension largely depend on absolute BP values, evidence from observational studies and post-hoc analyses of data from clinical trials have indicated that these outcomes might also depend on increased BP variability (BPV). Increased short-term and long-term BPV are associated with the development, progression, and severity of cardiac, vascular, and renal damage and with an increased risk of cardiovascular events and mortality. Of particular interest are the findings from post-hoc analyses of large intervention trials in hypertension, showing that within-patient visit-to-visit BPV is strongly prognostic for cardiovascular morbidity and mortality. This result has prompted discussion on whether antihypertensive treatment should be targeted not only towards reducing mean BP levels but also to stabilizing BPV with the aim of achieving consistent BP control over time, which might favour cardiovascular protection.

A large body of evidence has consistently supported the relationship between blood pressure (BP) levels and the risk of cardiovascular complications. In recent years, several independent studies have also indicated that this risk may not only depend on the magnitude of the blood pressure elevation per se but also on the presence of other associated conditions such as increased blood pressure variability. This concept has been supported by a series of reports, most of which post hoc analyses of clinical trials in hypertension, showing that increasing values of BP variability (BPV) (either in the short term, in the midterm, or in the long term) may predict development, progression, and severity of cardiac, vascular, and renal organ damage, as well as cardiovascular events and mortality. Remarkably, studies conducted in populations at high cardiovascular risk have shown increasing values of BPV in the individual subjects (so-called intra- or within-individual BPV) to be strong predictors of cardiovascular morbidity and mortality, even to a larger extent than average BP values. However, in subjects at low to moderate cardiovascular risk, the contribution of BPV to cardiovascular risk prediction over and beyond average BP values has been shown to be only moderate. The aim of this paper is to critically review the evidence addressing the prognostic relevance of different components of BPV addressing a yet open question, i.e., whether routine assessment of BPV in clinical practice should be regarded as an additional target of antihypertensive treatment to improve cardiovascular protection.

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