Hypertension is a common disorder that affects a large proportion of the community. It is usually asymptomatic and is detected on routine examination or after the occurrence of a complication such as a heart attack or stroke. 
Hypertension has been defined in joint guidelines by American learned bodies (American College of Cardiology [ACC] and American Heart Association [AHA] among others)  and also by the British Society of Hypertension  and the European Society of Hypertension.  There are differences in the definition of hypertension between guidelines.
The 2017 ACC/AHA guidelines for the prevention, detection, evaluation, and management of high blood pressure in adults defines hypertension as any systolic blood pressure measurement of ≥130 mmHg or any diastolic blood pressure measurement of ≥80 mmHg.  ACC/AHA blood pressure categories are defined as follows:
Elevated blood pressure: systolic blood pressure of 120-129 mmHg and diastolic blood pressure of <80 mmHg
Stage 1 hypertension: systolic blood pressure of 130-139 mmHg and/or diastolic blood pressure of 80-89 mmHg
Stage 2 hypertension: systolic blood pressure of ≥140 mmHg and/or diastolic blood pressure of ≥90 mmHg.
The 2017 ACC/AHA guidelines definition represents a more aggressive approach to diagnosis and treatment of hypertension compared with Joint National Committee (JNC) 7 and JNC 8 recommendations, where blood pressure in the range of 120-139 mmHg/80-89 mmHg is considered pre-hypertension and blood pressure >140/90 mmHg is considered elevated.  
Publication of the 2017 ACC/AHA guidelines has prompted widespread debate, and there are calls for the recommendations to be revisited. Implementing the guidelines would increase the prevalence of hypertension by 26.8% in the US. Critics are concerned that labelling more patients as hypertensive could increase psychological morbidity, as well as exposing lower-risk patients to the potential harm of antihypertensive medications. 
The 2017 ACC/AHA guidelines were mainly based on the results of the SPRINT trial, which investigated intensive or standard hypertension treatment in people with a systolic blood pressure of ≥130 mmHg with an increased cardiovascular risk (but without diabetes).  Listen to our podcast for more on the controversy.
High-normal: systolic 130-139 mmHg and/or diastolic 85-89 mmHg
Grade 1: systolic 140-159 mmHg and/or diastolic 90-99 mmHg
Grade 2: systolic 160-179 mmHg and/or diastolic 100-109 mmHg
Grade 3: systolic ≥180 mmHg and/or diastolic ≥110 mmHg.
The National Institute for Health and Care Excellence guidelines use a definition of hypertension similar to the European guideline. 
Isolated systolic hypertension is also graded according to systolic blood pressure values in the ranges indicated, provided that diastolic values are <90 mmHg. 
Although different studies have used a variety of cut-off points for the diagnosis of hypertension in the community, any blood pressure >120 mmHg systolic is associated with an increased cardiovascular risk. The importance of hypertension is its relation to other cardiovascular risk factors and consequent overall cardiovascular risk.
The AHA defines resistant hypertension as: 
Clinic blood pressure >130/80 mmHg despite the concurrent use of at least 3 antihypertensive agents (including an ACE inhibitor or angiotensin receptor antagonist, a long-acting calcium channel blocker, and a diuretic) at maximum or maximally tolerated doses.
Patients who require 4 or more antihypertensive agents to achieve their target blood pressure are also considered to have resistant hypertension. The diagnosis requires the exclusion of white-coat hypertension and poor adherence with antihypertensive medication.
This topic addresses the assessment of hypertension in adults.
In the US, data from the National Health and Nutrition Survey (NHANES) suggest that 29% of adults (>18 years) are hypertensive (cut-off value 140/90 mmHg). This ranges from around 7% in those aged 18-39 years to 66% in those aged >60 years.  The prevalence may be higher in Western Europe. 
Globally, the overall prevalence of hypertension in adults is 30% to 45%, according to European guidelines, with a higher prevalence in men than in women (24% and 20%, respectively). 
Hypertension is more prevalent in black people than in white people, starting in childhood, with 76% of black men and women developing hypertension by age 55 years, compared with 55% and 40% of white men and women, respectively. 
The exact prevalence of hypertension is difficult to assess, as it is usually asymptomatic. Prevalence is expected to rise as the 'cut-off' value for hypertension is re-defined at a lower level.
Approximately 15% of patients with hypertension have resistant hypertension. 
Studies have shown that treatment of hypertension can reduce the incidence of future cardiovascular and cerebrovascular events.  The aim of early diagnosis and treatment of hypertension is to lower overall cardiovascular risk and prevent cerebrovascular events. The effects of chronic hypertension on organ systems are referred to as target organ damage.
Left ventricular hypertrophy, cardiovascular disease, cerebrovascular disease, hypertensive retinopathy, and nephropathy are the most common manifestations.  The presence of left ventricular hypertrophy is a poor prognostic sign, and regression of left ventricular hypertrophy improves prognosis.  Patients with resistant hypertension are at higher risk of experiencing cardiovascular and cerebrovascular events and developing chronic kidney disease. 
Guidelines on the management of hypertension emphasise the importance of calculating and managing the overall cardiovascular risk of a patient, rather than focusing only on blood pressure readings. The ACC and AHA have published an online tool to calculate patients’ 10-year and lifetime risk of atherosclerotic cardiovascular disease.  Treating associated cardiovascular risk factors such as obesity, diabetes, hypercholesterolaemia, and smoking are as important as managing hypertension in lowering overall cardiovascular risk.For individuals aged 40-70 years, each increment of 20 mmHg in systolic blood pressure or 10 mmHg in diastolic blood pressure across the entire blood pressure range from 115/75 to 185/115 mmHg doubles the risk of cardiovascular disease.
Meta-analysis has confirmed that lowering blood pressure reduces cardiovascular disease and death in people with baseline systolic blood pressure of 140 mmHg or higher.  However, primary preventive blood pressure lowering does not benefit people with lower baseline blood pressure (except those with pre-existing cardiovascular disease).  One Cochrane review found insufficient evidence to justify lower blood pressure targets (≤135/85 mmHg) in people with hypertension and cardiovascular disease. 
Senior Consultant Cardiologist
Sultan Qaboos University Hospital
SN is an author of a number of references cited in this topic.
Price-Evans Professor of Cardiovascular Medicine
University of Liverpool
National Institute for Health Research
Faculty of Medicine
GYHL is a consultant for Bayer/Janssen, BMS/Pfizer, Biotronik, Medtronic, Boehringer Ingelheim, Novartis, Verseon, and Daiichi-Sankyo; he is also a speaker for Bayer, BMS/Pfizer, Medtronic, Boehringer Ingelheim, and Daiichi-Sankyo. GYHL is an author of a number of references cited in this topic.
Professor of Epidemiology
Head of the Section of Epidemiology & Biostatistics
School of Population Health
University of Auckland
RJ declares that he has no competing interests.
Professor of Medicine
David Geffen School of Medicine at UCLA
AW declares that he has no competing interests. Unfortunately we have since been made aware that Professor Wilkinson is deceased.
Department of Clinical Pharmacology
St Mary’s Hospital
MS declares that he has no competing interests.
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