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 Thailand, the overall prevalence of hypertension increased from 21% in 2003 to 25% in 2014.

Hypertension remains to be one of the top causes of morbidity and mortality in Asia 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