2018 Korean Society of Hypertension Guideline for the Management of Hypertension: A Comparison of American, European, and Korean Blood Pressure Guidelines

The prevalence of hypertension in Korea has been steadily increasing during the past decade. In 2016, it was estimated that 29.1% and 25.9% of Korean adults above age 30 were hypertensive or prehypertensive, respectively, based on the Korean National Health and Nutrition Examination Survey (KNHANES).1 This prevalence is similar to the USA where 32% of adults were hypertensive based on the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2014.2 Compared with their American and European counterparts, there is a much stronger association between stroke and blood pressure (BP) for Asians, including Koreans. Asians are also more salt sensitive and have high sodium diets (>4 g per day) which contributes to their elevated rates of hypertension.3 The English version of the 2018 Korean Society of Hypertension (KSH) guideline for the management of BP was recently published in the August 2019 issue of Clinical Hypertension.1,4,5 The new guideline represents an update to the 2013 KSH documents and incorporates recommendations from the 2017 American College of Cardiology/American Heart Association (ACC/AHA) Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure and the 2018 European Society of Cardiology/European Society of Hypertension (ESC/ESH) Guideline for the management of arterial hypertension.2,6–9 In addition to guidance on proper technique, use of home and 24-h ambulatory BP monitoring, and preferred pharmacological therapies, the new guideline focuses on precise BP targets based on global cardiovascular risk stratification modified by the presence or absence of comorbidities and specific disease states. Accurate atherosclerotic cardiovascular disease (ASCVD) risk stratification presents a major challenge for Asian populations including Koreans. In the 2017 ACC/AHA hypertension guideline, the Pooled Cohort Equation (PCE)10 is used to estimate 10-year ASCVD risk and determine BP targets. The PCE is known to overestimate risk in Asian populations and is not a universal risk calculator for all ethnicities.11 The PCE has no separate risk calculator or correction factor for Asians or Hispanics and defaults to the White risk score. In the 2018 ESC/ESH guideline, the Systematic COronary Risk Evaluation (SCORE)12 system is used to estimate risk of the first fatal atherosclerotic event. Unlike the PCE, SCORE includes a correction factor for first-generation immigrants to Europe based on their country of origin.6 In the 2018 KSH guideline, risk stratification is based on Korean Medical Insurance Corporation (KMIC) study data that is drawn from a relatively young, healthy population (35–59 years old) in the 1990s and from high socioeconomic backgrounds, and therefore may underestimate the true ASCVD risk.13 There is also a risk score derived from the Korean Heart Study (KHS) termed the Korean Risk Prediction Model (KRPM) that was modelled after Framingham risk prediction algorithms. When the PCE was applied to the KHS population, it was found to overestimate ASCVD risk in men by 56.5% and underestimate the risk in women by 27.9%.11 The KRPM correlates well with KMIC data and may better estimate ASCVD risk in the elderly population as the mean age in KHS was significantly older [50.1 years (KHS) vs. 44.7 years (KMIC) and 51.8 years (KHS) vs. 42.3 years (KMIC) for men and women, respectively].11,14 In the updated Korean and European guidelines, cardiovascular risk is further stratified into risk groups based on BP, number of risk factors, subclinical organ damage, and presence of ASCVD, diabetes or chronic kidney disease (CKD). In the KSH guideline, these risk groups range from low to highest added risk; low risk (<5%), low added risk (5 to <10%), moderate added risk (10 to <15%), high added risk (≥15%), and highest added risk (≥20%).4 The ESC/ESH guideline uses the SCORE system to estimate risk of cardiovascular mortality and defines the groups as low risk (<1%), moderate risk (1 to <5%), high risk (5 to <10%), and very high risk (≥10%).6 The American guideline uses the PCE to stratify patients into low- (<10%) or high-risk (≥10%) categories to define BP thresholds for treatment and provides specific targets based on comorbidities such as diabetes, CKD, or valvular heart disease (Table 1).2 Cardiovascular risk stratification groups KMIC, Korean Medical Insurance Corporation; PCE, Pooled Cohort Equation; SCORE, Systematic COronary Risk Evaluation. Cardiovascular risk stratification groups KMIC, Korean Medical Insurance Corporation; PCE, Pooled Cohort Equation; SCORE, Systematic COronary Risk Evaluation. The major changes to the 2017 ACC/AHA BP guideline are the new definition of hypertension and lower BP goals. Prior to this update, the target BP was generally <140/90 mmHg. Stage 1 hypertension is now defined as a BP >130/80 mmHg and the new guideline recommends a target BP below this level for most adults.2 In contrast, the 2018 ESC/ESH hypertension guideline did not adopt these changes and defines Stage 1 hypertension as BP >140/90 mmHg. If treatment is well-tolerated, however, a BP goal <130/80 mmHg is endorsed.6 The new KSH hypertension guidelines generally follow the European recommendations and use a threshold of >140/90 mmHg to define Stage 1 hypertension, but generally aim for a target BP <140/90 mmHg vs. <130/80 mmHg in the American and European guidelines (Table 2). Compared with the 2013 KSH guideline, the 2018 recommendations have not changed with respect to the definition of hypertension, however, the new guideline now defines prehypertension as a BP of 130–139/80–89 mmHg, while a BP of 120–129/<80 mmHg [prehypertension (Stage 1) in the 2013 guideline] is now classified as elevated.8 Of note, the 2018 KSH guideline is similar to other Asian society recommendations including the 2019 Japanese Society of Hypertension (JSH) and the 2018 Chinese hypertension guidelines that also define hypertension as BP >140/90 mmHg.15,16 The JSH recommends a target BP of <130/80 mmHg, while the Chinese guideline recommends a target BP of <140/90 mmHg or <130/80 mmHg if treatment is well-tolerated.15,16 Blood pressure/hypertension definitions Blood pressure/hypertension definitions Hypertension management in the 2018 KSH guideline is similar to both the American and European guidelines. Lifestyle interventions, including diet optimization, weight loss, exercise, alcohol moderation, and smoking cessation, are the mainstay for BP control and endorsed by all three guidelines. This is especially important with the adoption of the new AHA/ACC definition of hypertension as BP >130/80 mmHg, where nearly 50% of Americans are now considered to be hypertensive.17 In the American guideline, patients who are hypertensive with overt ASCVD or PCE risk ≥10%, initiation of pharmacotherapy is recommended for BP >130/80 mmHg. For hypertensive patients with ASCVD risk <10%, pharmacological intervention is not endorsed unless BP >140/90 mmHg. In the Korean guideline, pharmacotherapy is recommended for BP >140/90 mmHg (except high-risk patients, then >130/80 mmHg), which is similar to the European guideline. Salt restriction is specifically emphasized due to increased salt sensitivity and high sodium intake in Asian countries. All guidelines provide recommendations for BP targets based on presence of specific disease states. The BP target for the general population is <130/80 mmHg in the American guideline, <140/90 mmHg (but <130/80 mmHg, if the treatment is well-tolerated) in the European guideline, and <140/90 mmHg in the Korean guideline. For patients at highest risk or with overt ASCVD, all endorse a target BP <130/80 mmHg. In addition, BP targets for patients with CKD and diabetes mellitus are also comparable (Table 3). Blood pressure goals by age and disease state Subclinical organ damage or cardiovascular disease. Blood pressure goals by age and disease state Subclinical organ damage or cardiovascular disease. The elderly are the most controversial management group in the BP guidelines. The KSH recommends a BP goal <140/90 mmHg for fit older adults between 65 and 79 years old. The office BP treatment threshold for adults ≥80 years old or frail elderly hypertensives is ≥160/90 mmHg, but if tolerating treatment well, it is reasonable to aim for <140/90 mmHg. These targets are similar to the European guideline, but much less aggressive than the American guideline that recommends BP <130/80 mmHg for most adults ≥65 years old. The lower BP threshold in the ACC/AHA guideline was derived primarily from results of the Systolic Blood Pressure Intervention Trial (SPRINT) that showed greater cardiovascular risk reduction for elderly patients (age ≥ 75) with aggressive (<120 mmHg) vs. standard BP (<140 mmHg) targets.18 The KSH guideline contends that the ACC/AHA ASCVD score is not applicable to the Korean population and that the method of BP assessment used in SPRINT (automated office BP) is not performed routinely in clinical practice and may correspond to a conventional systolic BP measurement that is 10–15 mmHg higher.17 The 2018 KSH hypertension guideline is remarkably similar to the 2018 European update with respect to definitions and treatment goals for hypertension and does not adopt the more aggressive BP targets of the American guideline. All recommend lower BP goals for very high-risk patients including those with overt ASCVD, CKD, and diabetes mellitus. While the Korean and European guidelines endorse higher BP thresholds for elderly patients, the Americans recommend the same target for all patients, regardless of age. A critical need is the development of a more precise ASCVD risk assessment tool for Koreans. Current Korean risk tools, derived from national insurance data, may underestimate risk and are not representative of the general population. The American ASCVD risk calculator likely overestimates risk in certain Asian subgroups, including Koreans, while the European guideline relies on a risk multiplier based on country of origin to modify the risk score. Despite these differences, implementation of the new KSH guideline will hopefully lead to improvements in BP control rates in Korea and reduce the burden of hypertension-associated cardiovascular disease. Conflict of interest: E.Y.: Advisory Board: Clocktree; Research Grants: Amgen. No other conflicts for remaining authors. References are available as supplementary material at European Heart Journal online.