Hypertension is an important cardiovascular risk factor and the commonest chronic disease in Hong Kong, with a prevalence of 27.7% among people aged ≥15 years.1 The Primary Care Office of the Department of Health first published the Hong Kong Reference Framework for Hypertension Care for Adults in Primary Care Settings (Reference Framework) in 2010.2 Drawing on international evidence of best practice, the Reference Framework provides an evidence-based reference to primary healthcare professionals in the identification and management of hypertension in Hong Kong. To ensure the Reference Framework reflects latest medical development and evidence, it is updated regularly with expert advice from the Advisory Group on Hong Kong Reference Framework for Care of Diabetes and Hypertension in Primary Care Settings (Advisory Group). The Advisory Group comprises representatives from academia, relevant Colleges of the Hong Kong Academy of Medicine, and professional organisations.

In 2017, the American College of Cardiology (ACC) and the American Heart Association (AHA) released guideline recommendations using lower blood pressure (BP) values to define hypertension as systolic BP (SBP) ≥130 mm Hg and/or diastolic BP (DBP) ≥80 mm Hg.3 This recommendation is in contrast to the prevailing consensus of SBP ≥140 mm Hg and/or DBP ≥90 mm Hg adopted by the World Health Organization and other international guidelines.4 The BP goal of hypertensive therapy was also lowered to <130/80 mm Hg in the new ACC/AHA guideline.3 It is foreseeable that these new recommendations would arouse concern regarding the diagnosis and management of hypertension at individual patient care level, as well as issues related to disease labelling, changes in epidemiology, and the applicability of these recommendations to other populations. Even within the United States, the recommendations in this guideline were not unanimously agreed with among different authorities, and the application of these recommendations remains controversial.5 6 There is also little understanding of how these recommendations translate to non–United States populations, and there is currently no general consensus on the adoption of these recommendations in Hong Kong.

The aim of this study was to review the relevant literature, discuss the benefits and potential harms of setting lower BP values in the diagnosis and management of hypertension, and suggest updated recommendations on care for individuals with uncomplicated hypertension in the context of the primary care settings in Hong Kong.

Hypertension is a well-known modifiable risk factor for cardiovascular disease. It is associated with a number of adverse outcomes such as stroke, myocardial infarction, heart failure, peripheral artery disease, end-stage renal disease, and premature death.7 Meta-analyses of observational prospective studies suggested that people with SBP 120 to 139 mm Hg and/or DBP 80 to 89 mm Hg may also be at risk of cardiovascular events.8 9 10 11 12 13 14 15 16 17 For this group of people, it was observed that the higher the BP was, the higher the cardiovascular risk was, in general. However, the risk was less significant and less clearly established in Asians, except for the risk of stroke which was shown to be lower, similar to, or even higher than that for non-Asians from different meta-analyses. 8 9 10 11 12 13 14 15 16 17 The benefit of lowering BP to <140/90 mm Hg is well established. A meta-analysis showed that, when compared with treatment with a mean BP goal of 140/81 mm Hg, more intensive treatment with a lower mean BP goal of 133/76 mm Hg provided additional benefits on reducing the risk of major cardiovascular events, myocardial infarction, stroke, and albuminuria.18 However, although it was shown that treatment with a BP goal of <140/90 mm Hg lowered cardiovascular risk in general, further reductions in BP may further reduce the risk only of stroke.19 This relationship between BP values and the risk of stroke is also seen in the Chinese population. A study involving 17 720 Chinese uncomplicated hypertensive adults concluded that an SBP goal of 120 to 130 mm Hg resulted in the lowest risk of first stroke.20

Since the above findings were mostly from meta-analyses based on observational prospective studies, it may be worthwhile to have a brief discussion on the SPRINT21 trial and the ACCORD22 trial, which were the two major randomised controlled trials on lower BP goals. The participant characteristics were different in these two trials; SPRINT involved hypertensive patients with increased cardiovascular risk but no history of diabetes mellitus or stroke, whereas ACCORD included patients with type 2 diabetes mellitus.21 22 Both trials compared the clinical outcomes and adverse events in an intensive treatment group (SBP <120 mm Hg) and a standard treatment group (SBP <140 mm Hg). The results regarding the primary outcome were different in the two trials. The SPRINT trial concluded that the intensive BP-lowering treatment significantly lowered rates of heart failure, fatal major cardiovascular events, and all-cause mortality.21 In contrast, the ACCORD trial failed to demonstrate such cardiovascular benefits in the intensive treatment group. The ACCORD trial concluded that intensive BP-lowering treatment did not reduce the rate of the primary composite outcomes of fatal and non-fatal major cardiovascular events.22

There was concern regarding the use of unattended automated office BP in the SPRINT trial; automated office BP had not been used in any previous major randomised controlled trials (such as ACCORD) on BP-lowering treatment.23 When compared with conventional office BP measurement, automated office BP may result in lower BP values due to the absence of the white-coat effect. Therefore, it has been suggested that the BP values reported in SPRINT may actually correspond to conventional office SBPs of 130 to 140 mm Hg and 140 to 150 mm Hg in the more intensive and less intensive BP-lowering treatment groups, respectively.7 It is unclear if these findings can be extrapolated to hypertensive patients in Hong Kong.

In both SPRINT and ACCORD trials, significantly higher rates of adverse events were observed in patients treated with lower BP goals (ie, the intensive treatment group). In these groups, patients used a larger average number of antihypertensive medications than those in the standard treatment group. The recorded adverse events included hypotension, electrolyte abnormality, and acute kidney injury.21 22 Recent systemic reviews and meta-analyses have proposed that intensive BP-lowering treatment increases the risk of cardiovascular death without observable benefits; these studies have concluded that there is insufficient evidence to justify the lower BP goal.24 25 26 A large retrospective cohort study in Hong Kong, which involved around 100 000 Chinese patients with diabetes mellitus receiving primary care services, identified that the SBP range for the lowest risk of cardiovascular diseases and all-cause mortality was 130 to 134 mm Hg. In addition, a J-curve relationship between SBP and all outcomes of fatal and non-fatal cardiovascular diseases was observed, and patients with SBP <125 mm Hg were found to have significantly higher hazard ratio to all composite outcomes.27

Isolated systolic hypertension—an elevation in SBP but not DBP—is prevalent in older adults.28 29 Because interventions that lower SBP also reduce DBP, intensive SBP reduction in patients with isolated systolic hypertension may also result in lower values of DBP. Low DBP is associated with increased risk of target-organ hypoperfusion and cardiovascular events.28 29 30 For example, most ventricular myocardial perfusion occurs during diastole; therefore, a lower DBP could potentially lead to myocardial hypoperfusion and associated damage, especially in individuals with left ventricular hypertrophy or coronary artery disease.30 It has also been suggested that low DBP is associated with an increase in all-cause mortality.31

The Advisory Group regularly reviews the latest scientific evidence and recommendations from different professional organisations. The Advisory Group has noticed that there is currently inadequate evidence and lack of general consensus to support a change to the definition of hypertension in Hong Kong. Therefore, the Advisory Group agreed that the Reference Framework definition of hypertension should remain unchanged as a BP of ≥140/90 mm Hg.

Hypertensive patients are known to have a higher cardiovascular risk if they have other risk factors such as smoking, obesity, sedentary lifestyle, or elevated lipids or glucose; hence, a global risk approach should be included in assessing the cardiovascular risk of an individual patient.32 Although some evidence has suggested that a lower BP may provide greater benefit for patients with higher cardiovascular risk, there is also an increased risk of treatment noncompliance and serious adverse events from treatment if the BP is pushed too low, especially in older patients. It is, therefore, appropriate to determine the treatment goal on an individual basis after balancing the benefits and potential harms of having a lower BP goal in the context of that individual. Taking these into account, the Advisory Group endorses the approach of setting the BP goal with the consideration of age, underlying cardiovascular risk factors, and tolerability to treatment of the individual patient, instead of a single BP goal for all patients. This approach echoes the recommendation of recently published international guidelines.7 The Advisory Group recommends that the initial BP goal of therapy for individuals with uncomplicated hypertension should be <140/90 mm Hg; and for individuals who can tolerate it, the BP goal should be ≤130/80 mm Hg. A lower BP is advisable for young or overweight/obese patients, smokers, and patients with other cardiovascular risk factors.

Hypertension is an important cardiovascular risk factor and the commonest chronic disease in Hong Kong. Primary care physicians play an important role in the early diagnosis, prompt assessment and proper management of hypertension. The Reference Framework aims to provide updated evidence-based recommendations to support and influence the current practice of primary care physicians in Hong Kong, and to reduce the burden of long-term cardiovascular sequelae for hypertensive patients.

All authors have contributed to the concept or design of this study, acquisition of data, analysis or interpretation of data, drafting of the manuscript, and critical revision for important intellectual content. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

We would like to thank the members of the Advisory Group for their invaluable contributions in the development and update of the Reference Framework.

As an editor of the journal, MCS Wong was not involved in the peer review process. All other authors have disclosed no conflicts of interest.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

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