CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF PREHYP ERTENSION
Global health is facing a dramatic change that is characterized by the relentless worldwide spread of non-communicable diseases, which threaten the health and economies of all countries. In Sub-Saharan African countries, urbanization and globalization with the associated changes in lifestyle have caused a surge in the mortality and morbidity from non-communicable diseases, especially cardiovascular disease.
Cardiovascular disease (CVD) is considered to be a major cause of death in most developed countries.
However in the developing countries, more attention towards the endemic communicable and poverty-related diseases have allowed the epidemics of CVD to insidiously establish without attracting global attention or local action.
Hypertension is a major modifiable risk factor for cardiovascular morbidity and mortality. The relationship between blood pressure (BP) and the risk of cardiovascular
disease is direct, graded, and continuous over a wide range,
beginning at 115 mm Hg systolic and 75 mm Hg diastolic blood pressure.
This correlation is noted in men and women, young and old and amongst individuals from various ethnic and racial backgrounds.
Acknowledging this relationship between blood pressure and cardiovascular disease risk, the United States of America’s Joint National Committee On Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7) promulgated the concept of
“pre-hypertension” into the guideline for the management of blood pressure in 2003.
This new concept is defined as systolic blood pressure between 120 and 139mmHg and/or diastolic blood pressure between 80 and 89 mmHg. The term pre-hypertension was originally coined in 1939 by Robin and Brucer.
This was
based on their study, which showed that future hypertension will originate from pre- hypertension and that the mortality rate of people with pre-hypertension roughly doubles that of individuals with normal blood pressure (<120/80mmHg).
Despite the recognized associated mortality of prehypertension, they did not formulate treatment guideline. Following their postulation various terminologies have been used to describe pre- hypertension including transient hypertension, borderline hypertension, or high-normal BP. Although the terminology has changed, there is consensus that prehypertension is a precursor of hypertension and that it is associated with an excess morbidity and death from cardiovascular disease. 5-7
The prevalence of pre-hypertension is high worldwide but varies with differences in socio-demographic characteristics and pattern of cardiovascular disease risk factors of the population studied
. The prevalence of pre-hypertension amongst United States of America (U.S.A.) adult population was 31% in 2004.
A cross-sectional study in an adult family practice population in Canada reported a prevalence of 30.6% in 2008.
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The prevalence of pre-hypertension reported for Ghanaian adults was 40% in 2008.
A retrospective study on newly presenting diabetics in Maiduguri, Nigeria reported a prevalence of 36% in 2008.
More recently, a prevalence rate of 58.7% (men 59.2%, women 58.2%) was observed amongst the Hausa and Fulani ethnic groups in Sokoto, Nigeria in 2010.
To provide a framework for understanding the patho-physiology and treatment options of pre hypertension, it is important to understand factors involved in the regulation of both normal and elevated arterial blood pressure. Cardiac output and peripheral resistance are the primary determinants of blood pressure. Each of these determinants of blood pressure is affected in turn by a variety of factors.
Studies have demonstrated the important role of social, behavioural, and metabolic factors on blood pressure levels. 14, 15
The identified social risk factors include age, sex, and educational level. 14-18 Behavioural risk factors included salt intake, alcohol consumption, smoking and physical inactivity. 14,19 Metabolic-related risk factors include overweight/obesity, dyslipidaemia, insulin resistance, metabolic syndrome, proteinuria, hyper-uricaemia and diabetes mellitus. Abnormalities in circulating markers of inflammation, such as C-reactive proteins, interleukin 6, and tumor necrosis factor are also important determinants. 19-21
Adults with pre-hypertension are known to have a higher prevalence of other cardiovascular disease risk factors. Manious et al reported that about 93% of pre- hypertensive subjects have more than one other cardiovascular risk factor abnormality.
The determinants of progression to hypertension include advancing age, family history of hypertension, baseline systolic or diastolic blood pressure, high body mass index (BMI), presence of diabetes mellitus (DM), increased salt intake, and alcohol consumption 23,24 . These determinants increase the risk of progression of prehypertension to hypertension in genetically predisposed individuals through neuro-hormonal (renin-angiotensin – aldosterone and sympathetic nervous systems) activation.
The etiology and pathogenesis of prehypertension are poorly understood. However, it has been postulated that the neuro-humoral, renal, metabolic, race, genetic, and environmental factors are probably related to the development of prehypertension. 13, 25
A large number of cohort studies have shown that pre-hypertension is associated with a variety of chronic diseases such as coronary artery disease, heart failure, diabetes mellitus, dyslipidaemia, stroke and overweight/obesity. 26,27 The risk ratios of these cardiovascular diseases increased across the blood pressure gradient through normotension, prehypertension and hypertension. This clustering of cardiovascular diseases with prehypertension increases the cardiovascular disease risk of Diagnostic evaluation of prehypetensive subjects mainly involves thorough history taking and physical examination. Laboratory evaluation for global risk factor assessment is controversial depending on different hypertension treatment guidelines. 5, 28, 29
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Management of prehypertension is multifaceted because of the multi-factorial hypothesis of its patho-physiology. The goal of management is to intervene and prevent the documented relationship between prehypertension and cardiovascular disease. The management include patient education and counselling, lifestyle modifications and pharmacological treatment in selected patients.
Patient education and counselling is fundamental to the management of prehypertension. Patients are informed about the risk factors, natural course and the associated risk of cardiovascular diseases. An informed patient will be motivated to take charge of the risky lifestyles that influence the development of prehypertension. Life style modification is the main stay in management of prehypertension. The goal of life style modification is to optimize blood pressure to an acceptable range, prevent age- related increases in blood pressure, and prevent cardiovascular-related events in patients without compelling indication such as diabetes mellitus and chronic kidney disease.
Prehypertensive individuals should primarily be advised to modify their lifestyle to lower their blood pressure to normal values (systolic/diastolic blood pressure <120/80 mmHg).
The recommended lifestyle modifications include weight reduction, diet therapy, reduction of sodium intake, regular aerobic physical activity; smoking cessation and moderate alcohol consumption.
These types of non-pharmacological treatment for pre- hypertension have been proven through clinical trials to significantly lower blood pressure. It has been shown to prevent progression to hypertension and cardiovascular disease. 30, 31 In addition lifestyle modifications also benefit persons with diabetes mellitus, dyslipidaemia, the metabolic syndrome and overweight/obesity. 28, 29
The success of lifestyle modifications depend on the individual’s adherence and influence of family members. The management of prehypertension is patient and family centred. In addition to the above recommended dietary therapy, other dietary plans that have been proven to have blood pressure- lowering effect include Mediterranean diet and vegetarian diet. 32, 33 Other dietary therapies that were tried in smaller clinical trials include soya beans, omega-3 fatty acids and flavanol-rich cocoa. Even though, these interventions were proven to lower blood pressure, they are not recommended until after well designed randomized trials. 34,35
Pharmacological treatment of prehypertension is a treatment option for high risk group patients with co-morbidities such as diabetes mellitus, chronic kidney disease and cardiovascular diseases. The goal of pharmacological treatment is to control blood pressure and reduce morbidity and mortality in patients with renal disease and diabetes. 5, 28, 29 Prehypertension is associated with some complications if not treated early. These include sub-clinical target organ damage such as left ventricular hypertrophy, micro- albuminurea and increase in common carotid artery intima-media thickness and clinical
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target organ damage such as coronary heart disease, heart failure and cerebro-vascular accident.
These complications are commoner among prehypertensives when compared to normotensives. This was attributed to the endothelial dysfunction, inflammatory risk factors and high prevalence of cardiovascular risks often associated with
Prevention of prehypertension is the cornerstone in the management of prehypertension. Primary prevention involves health promotion of the general population without any known risk factors. This can be achieved through routine health education and counseling for adoption of a healthy lifestyle. These primary measures advocate consumption of an overall healthy diet, maintenance of a healthy body weight, increase in physical activity and avoidance of smoking. Secondary prevention involves early detection of prehypertension and adoption of lifestyle modifications to avoid progression to hypertension and cardiovascular disease. Early detection can be achieved through routine blood pressure measurement at every contact with patients and assessment of the associated risk factors. 5, 28, 29
1.2 STATEMENT OF THE PROBLEM
The prevalence of pre-hypertension is growing globally and is therefore, a concern to health care providers. This condition has high prevalence and is associated with other cardiovascular risk factors such as obesity, dyslipidaemia, insulin resistance, metabolic syndrome and diabetes. Cardiovascular disease is a major cause of death worldwide. Hypertension is a major modifiable risk factor of cardiovascular morbidity and mortality. This documented relationship between blood pressure and cardiovascular disease risk is a continuum across blood pressure which extends down to prehypertensive range.
Given the prevalence of prehypertension in the family practice population,
population with pre-hypertension may constitute a significant proportion of patients seen in outpatient clinic, who probably come for preventive and curative health services, which if not checked and managed can progress to hypertension and its complication. The limited healthcare personnel and facilities, the busy nature of a typical clinic in our environment coupled with the level of poverty in the environment, especially rural in areas, can all hinder early screening and intervention. A previous study reported that very few prehypertensive patients (1.9%) were told by their primary care clinicians about their diagnosis.
With these, pre-hypertension can easily progress to hypertension and cardiovascular diseases, which are major drain of individual, family and state resources. Moreso, previous studies have shown that hypertension was the most prevalent cardiovascular disease in the north-west Nigeria
and Kano had the highest prevalence of hypertension in Nigeria.
But studies on the pattern and determinants of pre- hypertension are scarce. Hence routine screening and advocacy for prevention are of urgent need in the our environment.
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1.3 OBJECTIVES
MAIN OBJECTIVE To describe the pattern of pre-hypertension among adult patients at the General Out- patient Clinic of Aminu Kano Teaching Hospital, Kano in order to increase physicians’ awareness about this cardiovascular risk factor in our environment and routinely encourage early detection and intervention.
SPECIFIC OBJECTIVES 1. To determine the prevalence of pre-hypertension among adults attending the General Out-patient Clinic of Aminu Kano Teaching Hospital. 2. To identify associated cardiovascular risk factors among the study participants. 3. To identify associated co-morbidities among the study participants. 4. To identify the determinants of pre-hypertension among study participants.
1.4 JUSTIFICATION FOR THE STUDY
Pre-hypertension is highly prevalent and is associated with the traditional cardiovascular risk factors linked to hypertension, such as obesity, diabetes mellitus and dyslipidaemia. This clustering of cardiovascular disease risk factors among persons with prehypertension suggest that persons found to have prehypertension should be screened for other cardiovascular disease risk factors. A large proportion of the population in our family practice
need close surveillance of blood pressure levels because of the high prevalence
of pre-hypertension. The risk of progression to hypertension and cardiovascular events that is associated with prehypertension can be prevented through routine screening and early intervention. Prevention of pre-hypertension should be an important goal for primary care patients and health concern for health personnel. Hence, the role of the Family Physician in terms of routine screening, counselling about lifestyle modification and advocacy for prevention cannot be over-emphasized. Family Physicians as frontline specialist doctors and advocate for patients are in the best position to abate the current trend of epidemics of cardiovascular disease. Hypertension, the major modifiable risk factor of
cardiovascular disease can be controlled by mere routine screening and early adoption of lifestyle modification so as to prevent the inevitable consequences on individual patient, family, community and continent at large. This study is being undertaken to increase awareness of pre-hypertension in environment, encourage physicians to routinely screen for it and its determinants in high risk populations and offer early intervention.
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