Commentary

Until this review by Appel et al, clinicians did not know what to make of ABP because evidence on prognosis had not been consolidated. ABP is a non-invasive automated technique measuring BP at intervals usually over a 24 hour period. ABP can identify absolute BP, white coat hypertension (WCH), non-dipping (night-time BP <10% lower than daytime BP), and reverse dipping (night-time BP higher than daytime BP). Most people are nocturnal dippers. Their systolic BP (SBP) and diastolic BP (DBP) drop about 10–20% compared with average daytime levels.

Appel et al have structured this 235 page evidence-based report to answer key questions on the management of this epidemic of hypertension affecting 25% of the US population. Higher ABP levels and patterns in cross-sectional studies were confirmed to be positively associated with BP related target organ damage. In prospective ABP studies, higher sustained BP and non-dipping or reverse dipping patterns were positively associated with increased risk of CVD events, highly so for secondary hypertension as in end stage renal disease and type 2 diabetes.

ABP is useful for diagnosing WCH, comprising approximately 20% of hypertensive patients. WCH predicts a reduced CVD risk compared with sustained hypertension.¹ The question of whether risk in WCH is equivalent to risk in normotension, or whether to withhold drug therapy, cannot be answered by Appel et al because of insufficient reported data. For SMBP, although half of reviewed studies confirmed an association of its use with reduced BP, no conclusion could be made between its use and reduced CVD outcome, again because of insufficient published data.

Health funders in the US are now incorporating these data in decision making by using ABP to directly estimate a patient’s cardiovascular risk when WCH or various types of dipping are suspected.² Clinical management of hypertension as routinely practised may be changing.