The World Health Organization has identified hypertension, or high blood pressure, as the leading cause of cardiovascular mortality. The World Hypertension League (WHL), an umbrella organization of 85 national hypertension societies and leagues, recognized that more than 50% of the hypertensive population worldwide are unaware of their condition. To address this problem, the WHL initiated a global awareness campaign on hypertension in 2005 and dedicated May 17 of each year as World Hypertension Day (WHD). Over the past three years, more national societies have been engaging in WHD and have been innovative in their activities to get the message to the public. In 2007, there was record participation from 47 member countries of the WHL. During the week of WHD, all these countries – in partnership with their local governments, professional societies, nongovernmental organizations and private industries – promoted hypertension awareness among the public through several media and public rallies. Using mass media such as Internet and television, the message reached more than 250 million people. As the momentum picks up year after year, the WHL is confident that almost all the estimated 1.5 billion people affected by elevated blood pressure can be reached.
According to the American Heart Association (AHA), approximately 86 million adults (34%) in the United States are affected by hypertension, which is defined as a systolic blood pressure (SBP) of 140 mm Hg or more or a diastolic blood pressure (DBP) of 90 mm Hg or more, taking antihypertensive medication, or having been told by clinicians on at least 2 occasions as having hypertension.  Substantial improvements have been made with regard to enhancing awareness and treatment of hypertension. However, a National Health Examination Survey (NHANES) spanning 2011-2014 revealed that 34% of US adults aged 20 years and older are hypertensive and NHANES 2013-2014 data showed that 15.9% of these hypertensive adults are unaware they are hypertensive; these data have increased from NHANES 2005-2006 data that showed 29% of US adults aged 18 years and older were hypertensive and that 7% of these hypertensive adults had never been told that they had hypertension. 
High blood pressure is classified as either primary (essential) high blood pressure or secondary high blood pressure. About 90–95% of cases are primary, defined as high blood pressure due to nonspecific lifestyle and genetic factors. Lifestyle factors that increase the risk include excess salt in the diet, excess body weight, smoking, and alcohol use. The remaining 5–10% of cases are categorized as secondary high blood pressure, defined as high blood pressure due to an identifiable cause, such as chronic kidney disease, narrowing of the kidney arteries, an endocrine disorder, or the use of birth control pills.
Adapted from: Chobanian AV, Bakris GL, Black HR, et al, and the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; National Heart, Lung, and Blood Institute; National High Blood Pressure Education Program Coordinating Committee. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension. Dec 2003;42(6):1206-52. 
^ Jump up to: a b c Members, Authors/Task Force; Mancia, Giuseppe; Fagard, Robert; Narkiewicz, Krzysztof; Redon, Josep; Zanchetti, Alberto; Böhm, Michael; Christiaens, Thierry; Cifkova, Renata (13 June 2013). "2013 ESH/ESC Guidelines for the management of arterial hypertension". European Heart Journal. 34 (28): 2159–219. doi:10.1093/eurheartj/eht151. hdl:1854/LU-4127523. ISSN 0195-668X. PMID 23771844. Archived from the original on 27 January 2015.
Many mechanisms have been proposed to account for the rise in peripheral resistance in hypertension. Most evidence implicates either disturbances in the kidneys' salt and water handling (particularly abnormalities in the intrarenal renin–angiotensin system) or abnormalities of the sympathetic nervous system. These mechanisms are not mutually exclusive and it is likely that both contribute to some extent in most cases of essential hypertension. It has also been suggested that endothelial dysfunction and vascular inflammation may also contribute to increased peripheral resistance and vascular damage in hypertension. Interleukin 17 has garnered interest for its role in increasing the production of several other immune system chemical signals thought to be involved in hypertension such as tumor necrosis factor alpha, interleukin 1, interleukin 6, and interleukin 8.
Dr Jacomien de Villiers qualified as a specialist physician at the University of Pretoria in 1995. She worked at various clinics at the Department of Internal Medicine, Steve Biko Hospital, these include General Internal Medicine, Hypertension, Diabetes and Cardiology. She has run a private practice since 2001, as well as a consultant post at the Endocrine Clinic of Steve Biko Hospital.
Usually, diastolic pressures will mirror systolic pressures, but as people age, the diastolic pressure tends to level out. Then, the form of hypertension that involves primarily the systolic pressure (called isolated systolic hypertension) becomes more common. In general, the greater the blood pressure for extended periods of time, the greater the potential for damage.
Hypertension is rarely accompanied by symptoms, and its identification is usually through screening, or when seeking healthcare for an unrelated problem. Some people with high blood pressure report headaches (particularly at the back of the head and in the morning), as well as lightheadedness, vertigo, tinnitus (buzzing or hissing in the ears), altered vision or fainting episodes. These symptoms, however, might be related to associated anxiety rather than the high blood pressure itself.