Hypertension Disease Background

Introduction

Hypertension is the medical term for high blood pressure (BP). 

Epidemiology

The World Health Organization (WHO) estimated hypertension to occur in 1.28 billion adults aged 30-79 years old and two-thirds of these are living in low- and middle-income countries. About 46% of adults with hypertension are not aware that they have hypertension while about 42% of adults with hypertension are diagnosed and managed, and only 21% (1 in 5 adults) have controlled hypertension. It must be noted that approximately 5-25% of adults with hypertension have secondary causes.

The prevalence of hypertension in Asia is approximately 49.4% in men and 43.6% in women. In Vietnam, the prevalence was 25.1% based on a national survey from 2001-2008 among those aged ≥25 years old. Based on the May Measurement Month, the prevalence of hypertension was increasing with prevalence rates of 28.7% in 2017, 30.3% in 2018, and 33.8% in 2019.  

The overall crude prevalence of hypertension in China based on the 2012-2015 national survey was 27.9% among those ≥18 years old, directly correlated with increasing age. In Hong Kong, hypertension is one of the most common diseases with prevalence rates ranging between 27.7-29.5% among those ≥15 years old. In Korea, approximately 30% of Koreans aged ≥30 years old have hypertension.  

Over one-third of the population of Indonesia is diagnosed with hypertension. The prevalence rate was 34.5% based on the May Measurement Month in 2017 and 34.1% based on previous surveys in 2018. The National Health and Morbidity Survey in Malaysia reported that there was an increasing trend in the overall prevalence of hypertension which were 34.6% in 2006, 33.6% in 2011, and 35.3% in 2015 among those ≥18 years old.  

The Philippine Heart Association’s PRESYON-4 reported that the point prevalence in the Philippines increased to 34% in 2020 from 28% in 2013. Nevertheless, the National Nutrition Survey reported that the prevalence decreased from 23.9% in 2013 to 19.2% in 2018 among those 20-59 years old and 41.2% in 2015 to 35% among the elderly in 2018. The WHO reported that the prevalence of hypertension in Myanmar was 30.1% among those 25-64 years old in 2014, which was similar to the prevalence rate reported by a cross-sectional study that utilized data from a survey in 2009.  

The Singapore National Health Survey (NHS) in 2010 reported that the crude prevalence of hypertension in Singapore was decreasing from 27.3% in 1998, 24.9% in 2004, and 23.5% in 2010 among those 30-69 years old. Among 18-69 years old, the prevalence was 18.9% in 2010. In Thailand, however, the overall prevalence of hypertension increased from 21% in 2003 to 25% in 2014. In Vietnam, the prevalence was 25.1% based on a national survey from 2001-2008 among those aged ≥25 years old. Based on the May Measurement Month, the prevalence of hypertension was increasing with prevalence rates of 28.7% in 2017, 30.3% in 2018, and 33.8% in 2019.  

In India, the prevalence rate of hypertension was estimated to be between 20-30%, without considering the updated definition by the ACC/AHA. However, a study in 2017 concluded that applying the updated definition caused a significant increase in the prevalence rate to 40.6%.  

Hypertension remains to be one of the top causes of morbidity and mortality in these countries and although the level of awareness, treatment, and control are steadily increasing, they remain to be low.

Pathophysiology

Hypertension may be due to multiple factors including neural and chemical disorders, alterations of vascular caliber and elasticity, cardiovascular (CV) reactivity, and blood volume and viscosity.  

BP maintenance is complex and involves several physiological mechanisms including arterial baroreceptors, the renin-angiotensin-aldosterone system, atrial natriuretic peptide, endothelins, and mineralocorticoid and glucocorticoid steroids, which together manage the degree of vasoconstriction or vasodilation within the systemic circulation, and the retention of water and sodium to maintain adequate circulating blood volume and dysfunction in any of these processes can lead to hypertension development.  

Sympathetic neural activation modulates hypertension by enhancing vasoconstriction and vascular remodeling, producing renal renin via beta 1 adrenergic receptors in the juxtaglomerular apparatus and increasing renal sodium resorption and inflammation. Nephrogenic mechanism attributes BP increase to either decreased renal blood flow or to renal parenchymal disease.   

Etiology

Dietary intake factors associated with hypertension include high sodium intake, lower intake of potassium, calcium, or magnesium, lower intake of fruits, vegetables, plant proteins, or fiber, as well as alcohol and caffeine intake. Non-dietary factors include being overweight or obese, lower physical activity or fitness, sleep disturbances, psychosocial stressors, genetic variants, and even air pollution. Lastly, different medications may cause hypertension, including decongestants, nonsteroidal anti-inflammatory drugs (NSAIDs), Acetaminophen, amphetamines, antidepressants, atypical antipsychotics, immunosuppressants, oral contraceptives, systemic corticosteroids, angiogenesis and tyrosine kinase inhibitors, androgen deprivation therapy or androgen receptor antagonists. It must also be noted that abrupt withdrawal of medications such as clonidine and tizanidine, as well as the use of recreational drugs and herbal supplements, can also lead to hypertension.  

Classification

Classification of BP 

The classification must be based on the average of ≥2 properly measured, seated BP readings on each of ≥2 office visits. Various consensus guidelines are available as standard references for the definition of hypertension.¹

• Stage 1: Uncomplicated hypertension (without hypertension-mediated organ damage [HMOD], diabetes, established CV disease [CVD] or chronic kidney disease [CKD] stage ≥3)
• Stage 2: Presence of HMOD, diabetes, or CKD stage 3
• Stage 3: Presence of established CVD or CKD stage 4 or 5