PREVALENCE AND DETERMINANTS OF PREHYPERTENSION AMONG ADULT PATIENTS ATTENDING THE GENERAL OUTPATIENT CLINIC OF THE FEDERAL MEDICAL CENTRE, OWERRI, IMO STATE

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PREVALENCE AND DETERMINANTS OF PREHYPERTENSION AMONG ADULT PATIENTS ATTENDING THE GENERAL OUTPATIENT CLINIC OF THE FEDERAL MEDICAL CENTRE, OWERRI, IMO STATE

SUMMARY

Background: Recent studies have documented an increased risk of cardiovascular disease (CVD) in persons with systolic blood pressures of 120–139 mmHg and/or diastolic blood pressures of

80–89 mmHg, classified as prehypertension in the Seventh Report of the US Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. This study estimated the prevalence and determinants of prehypertension in adult patients attending the GOP Clinic of the Federal Medical Centre, Owerri.  

Methods: The study used data from participants in the population constituting of 369 consecutive subjects, 197 males and 172 females, who were recruited based on the inclusion criteria. A sample of 369 subjects, 18 years and above, completed an interviewer-administered questionnaire and had anthropometric and blood pressure measurements performed by the author using standardized procedures. Fasting blood glucose and lipid profile were measured using venous blood samples. Analyses yielded crude, and sex-specific prevalence estimates for prehypertension and other CVD risk factors. Odds ratios for associations of prehypertension with CVD risk factors were obtained using multivariate logistic regression.

Results: Prehypertension occurred in 39.57% of the study population and was associated with increased prevalence of other CVD risk factors. The major determinants of prehypertension in the study population were waist circumference, age, cigarette smoking and physical activity. Conclusion: It is recommended that appropriate lifestyle measures like regular aerobic exercise and avoidance of smoking, in addition to the DASH eating plan be adopted. Further studies are needed to determine the cause and effect relationship between prehypertension and

cardiovascular risk factors.

TABLE OF CONTENTS

 

Title Page I
Declaration

Certification

Ii Iii
Dedication

Acknowledgement

Iv

V

Table of Contents

List of Figures

List of Tables

Vi vii viii – x
List of Acronyms

Summary

xi – xii xiii
Chapter One: Introduction 1 – 11
Chapter Two: Literature Review

Chapter Three: Methodology

12 – 43

44 – 52

Chapter Four: Results 53 – 82
Chapter Five: Discussion 83 – 100
References 101 – 126
Appendix One: Questionnaire 127 – 129
Appendix Two: Consent form 130

Appendix Three: Ethical clearance Certificate                                                                    131

CHAPTER ONE

 

1.0       INTRODUCTION

Hypertension is an important worldwide public health challenge because of its frequency and concomitant risks of cardiovascular (CV) and kidney diseases1. It is one of the most prominent attributable risks for death throughout the world2. Worldwide, 7·6 million premature deaths (about 13·5% of the global total) and 92 million DALYs (6·0% of the global total) have been attributed to high blood pressure2,3. According to the World Health organization (WHO), 51% of stroke (cerebrovascular disease) and 45% of ischaemic heart disease deaths globally, are attributable to high blood pressure. Elevated BP is associated with a two to three times higher risk of developing

congestive heart failure4-6 and substantially increases the risk of stroke7,8.

 

Hypertension is well known to be a major risk factor for cardiovascular diseases (CVDs)2,9,10. CVD affect developed and wealthy countries and documented evidence reveals that more than 4.5 million deaths due to coronary artery disease (CAD) occur in the developing world. It is also projected that CAD mortality rates will double from 1990 to 2020, with approximately 82% of the increase attributable to the developing world11. There is currently the increased awareness that most developing countries are experiencing an “epidemiologic transition” in which causes of death are shifting from primarily infectious diseases to NCDs12-14. The high burdens of NCDs are highlighted by the estimates provided by the global burden of disease study and in the World Health Report 1999, which indicated that these disorders together contributed to 59% of global mortality (31.7 million deaths) and 43% of the global burden of diseases in 199815,16. The World

Health Report 1999 estimated that in 1998, 78% of the CVD burden of NCDs and 85% of the CVD burden arose from the low and middle income countries. The CVD burden afflicts both men and women, with CVD deaths accounting for 34% of all deaths in women and 28% in men in 199816. As the epidemic advance, the social gradient also reverses with the poor becoming the most vulnerable victims in both developed and developing countries17. The high burdens of CVD in the developing countries are attributable to the increasing incidence of atherosclerotic diseases, perhaps due to urbanization and higher risk factor levels (such as obesity, diabetes, dyslipidaemia, hypertension, etc), the relatively early age at which they manifest, the large sizes of the population, and the high proportion of individuals who are young adults or middle-aged in these countries. For example, about half of the deaths attributable to CVD in the developing countries in 1990 occurred below the age of 70 years, in contrast to about a quarter in the developed countries15. Such a pattern of premature CVD mortality is likely to haunt the developing countries even more in the future.

 

CVD is emerging as a major public health burden in sub-Saharan Africa, with hypertension being a major risk factor18. Recent reports indicate prevalence rates as high as 33% in some urban communities19,20. The high prevalence of hypertension is reflected in the increase in CVD mortality21. The relationship between blood pressure and risk of CVD events is continuous, consistent, and independent of other risk factors9. Conversely, even small reductions in BP lead to significant reductions in the incidence of stroke, myocardial infarction, and heart failure22.

 

Data from observational studies involving more than 1 milllion individuals have shown that death from both ischaemic heart disease and stroke increases progressively and linearly from levels as low as 115 mmHg systolic and 75 mmHg DBP upward23. These increased risks are present in individuals ranging from 40 to 89 years of age. For every 20 mmHg systolic or           10 mmHg diastolic increase in blood pressure, there is a doubling of mortality from both ischaemic heart disease and stroke. In addition, longitudinal data obtained from the Framingham Heart Study have indicated that BP values between 130–139/85–89 mmHg are associated with a more than twofold increase in relative risk from CVD as compared with those with BP levels below 120/80 mmHg24.

 

Hypertension is the most common cardiovascular disease in Nigeria25-27. Early hospital-based studies in Ibadan, Benin, and Port Harcourt, have shown that hypertension accounted for 40%,

16.5% and 25% respectively, of all patients admitted to the medical wards of these centers25-27. According to the 1997 report of National Non-communicable disease survey in Nigeria, the crude prevalence rate of hypertension was found to be 11.2%28. This survey showed that not less than 4.33 million Nigerians over the age of 15 years were hypertensive, with Kano having the highest prevalence while Malumfasi and Mangu, the lowest. Hypertension has been found to be more prevalent in the urban areas of Nigeria28-31. Physical activity has been shown to reduce the risk of hypertension and a strong positive correlation exists between the body mass index and hypertension. Positive family history of hypertension in at least one first degree relative was also found to increase the risk of developing hypertension.

 

The term prehypertension was conceptualized following a study in 1939, as it was observed that blood pressure measurements greater than 140/90 mmHg were associated with a sharp increase in mortality compared with lower measurements, giving rise to the usual clinical definition of hypertension32. In addition, systolic blood pressure in the range 120–140 mmHg, especially when occurring in younger individuals, was associated with progression to definitive hypertension and cardiovascular disease later in life. Systolic blood pressures of 120–140 mmHg were referred to as ‘danger zones’ for later development of hypertension, and individuals with blood pressure values in this range were referred to as having ‘prehypertension’.

 

In 2003, the concept of prehypertension was promulgated into guidelines for the management of blood pressure by the seventh report of the US Joint National Committee on Prevention, Detection, evaluation, and treatment of High Blood Pressure (JNC 7)9. Prehypertension was defined as a systolic blood pressure of 120–139mmHg and/or a diastolic blood pressure of 80–89 mmHg. Normal blood pressure is taken to be systolic BP less than 120 mmHg or diastolic BP less than 80mmHg while stage I hypertension is systolic BP of 140-159 mmHg or diastolic BP of 90-99 mmHg. However, Stage II hypertension is taken as systolic BP of 160 mmHg and above or diastolic BP of 100 mmHg or greater. The objectives of creating this blood pressure classification were to increase awareness of the importance of identifying individuals, in whom early intervention by adoption of healthy lifestyles could lower blood pressure, decrease the rate of progression to hypertensive levels, or to prevent hypertension entirely, thereby reducing the risk of cardiovascular disease. A further aim was to encourage insurance coverage for preventive services for individuals with prehypertension.

 

The impetus for creating the prehypertension blood pressure category came, at least in part, from a meta-analysis that included approximately 1 million individuals from 61 long-term epidemiological studies. The meta-analysis demonstrated that mortality from ischaemic heart disease and stroke in individuals aged 40–89 years increases in a log–linear relationship together with increases in both systolic and diastolic blood pressure23. For each 20mmHg increase in systolic blood pressure or 10mmHg increase in diastolic blood pressure over 115/75 mmHg, there is a two-fold increase in mortality associated with coronary artery disease and stroke. Furthermore, longitudinal data from the Framingham Heart study indicated that individuals formerly classified as having ‘normal’ and ‘high-normal’ blood pressure (120–139/80–89 mmHg) are at increased risk of developing full-blown hypertension and cardiovascular disease later in life than those who have an optimal blood pressure (<120/80 mmHg)33,34. It also showed that BP in the prehypertensive range preceded the diagnosis of hypertension in 90% of subjects aged ≥55 years34. In another longitudinal study, Winegarden showed that relative to normotensive subjects, the risk of hypertension was substantially higher among subjects with a high normal BP (130 to139/85 to 89 mmHg)35. However, whereas several reports have documented an increased risk of CVD among prehypertensive subjects, others suggest that prehypertension increases the risk of CVD only modestly or that this risk increases only when prehypertension is associated with

additional risk factors34,36-49. Recent studies suggest that the rates of progression and regression of prehypertension vary with age and gender, anthropometric, and biochemical measurements,

and family history42,43.

 

An additional rationale for use of the term prehypertension rather than high-normal or normal blood pressure is that the new classification would be more likely to make the affected individual follow healthcare recommendations; the word ‘high’ is often ignored and ‘normal’ is overvalued12.

 

Arguments against using the term prehypertension for the blood pressure range 120–139/80–89 mmHg include: the heterogeneity of the prehypertension category because the risk of progressing to hypertension and developing cardiovascular events is higher in patients with blood pressure 130–139/85–89 mmHg range than in those with blood pressure 120–129/80–84 mmHg; concern that the term prehypertension would create anxiety among the general public and would generate unnecessary medical visits, and the observation that some patients with prehypertension are at such high risk of cardiovascular disease that they require treatment beyond lifestyle interventions, such as medical antihypertensive therapy44.

 

Data on prehypertension in adults in the study environment are sparse, and little is known of the risk factors for prehypertension. This study was undertaken to identify the biosocial determinants of prehypertension status in the study locality, which includes a population that may be at risk of developing hypertension and/or coronary heart disease, but was previously classified as normotensive, and thus have long been overlooked.

 

1.1       STATEMENT OF THE PROBLEM AND PROBLEM ANALYSIS

 

In the last couple of years, there has been an increase in the number of hypertensive patients presenting to the General Out-patient (GOP) Clinic of the Federal Medical Centre, Owerri. Many of these patients presented with varied co-morbidities, with multifarious complications of hypertension including cerebrovascular accidents, heart failure, myocardial infarction, and end stage renal disease. These complications contributed significantly to deaths due to medical illnesses in the Hospital. A sizeable number of these complications are preventable through early intervention and adoption of healthy lifestyles which could reduce the BP, decrease the rate of progression of BP to hypertensive levels with age, or prevent hypertension entirely. Moreover, the increased urbanization and incessant adoption of Westernized lifestyles in addition to the dramatic surge in the number of fast food restaurants in Owerri, in the recent past and its possible implications on blood pressure, are critical public health challenges. This trend is worrisome considering the influence of junk food on cardiovascular health.

 

Prehypertension is a recognized risk factor for overt hypertension and has been associated with an increased risk of myocardial infarction, stroke, heart failure, and cardiovascular death, which are clinical scenarios that are of great concern to the family physician, given their long-term impact on health. The increasing incidence of heart failure and strokes, which are notable complications of hypertension in our locality, have not only reduced the quality of life of the affected individuals but also placed a huge burden on the health care facilities45-50.

Despite the importance of this new BP category and the rising BP levels in many sub-Saharan African countries, limited studies to date have assessed prehypertension in Nigeria42,51-56. Recent evidence suggests that BP levels and hypertension rates in Nigeria are among the highest in Africa31,46,51. The increased prevalence of hypertension in Nigeria is consistent with the higher

levels of stroke and CVD mortality45-50. This ugly trend needs to be checked in order to decrease the incidence and overall cardiovascular morbidity and mortality associated with increasing levels of blood pressure. The long-term benefits of targeting individuals with prehypertension with lifestyle modifications may be greater for low-income countries like Nigeria, where activities aimed at controlling clinical hypertension have to compete with many other pressing health challenges like malaria, `tuberculosis, and HIV/AIDS. This study was conceptualized and carried out to ascertain the proportion as well as the biosocial correlates of prehypertension at the GOP

Clinic of the Federal Medical Centre, Owerri.

 

1.2       JUSTIFICATION FOR THE STUDY

It is common knowledge that one of the major obstacles to the control of blood-pressure-related diseases in low and middle income countries is the dearth of appropriate primary healthcare services, which in the Nigerian context is compounded by the lack of political will on the part of policy makers to reasonably implement or fund healthcare programmes. This trend is worrisome and has been worsened by the persisting interaction between poverty, ignorance and disease, which abound in our environment. This again brings to light one of the key challenges facing the delivery of primary healthcare services in our setting and the need for primary prevention of hypertension cannot be overemphasized.

In view of the rising prevalence of hypertension and the great burden it imposes on the healthcare system and families in Nigeria, identification and monitoring of individuals with blood pressures that are within the prehypertensive range remains worthwhile. This study will provide the prevalence rate and determinants of prehypertension status in adult patients attending the General Out-patient Clinic of the Federal Medical Centre, Owerri. It will also bring to light the overall burden of the problem and the need for institutionalization of programmes that would be geared towards halting the progression of prehypertension to hypertension.

 

This study will afford the participants the opportunity of knowing their blood pressure reading in numbers, not just in words, as this has been identified as the first step in preventing and/or controlling high blood pressure. Knowing the BP reading in numbers will help to assess what the individual needs to do to lower the risks of developing future health problems. It will also afford the opportunity to alert individual patients and the clinician that early action can prevent serious health consequences later.  The study will also provide the opportunity to educate patients and their families concerning healthy lifestyles including the need to change one’s lifestyles such as losing weight if overweight, increasing physical activity, avoiding cigarette smoking and reducing salt intake, which have been shown to prevent the progressive rise in blood pressure and even lower it.  It will also impact positively on the awareness level of the study participants and the public, a key step to prevention and control of high blood pressure, which is an important public health problem.

 

The study will provide a framework for early identification of at risk individuals at the primordial level. It will also offer suitable agenda for the design and implementation of appropriate primary strategic measures for prevention and control of high blood pressure. This study will generate interest among stakeholders in health on the public health importance of prehypertension, and then hypertension, in view of its associated cardiovascular morbidity and mortality. The need to conduct a National Health Survey on prehypertension in Nigeria and strengthening of primary care services as has been done in other populations would be highlighted.

 

Studies have shown that prehypertension is common. Progression of prehypertension to       fullblown hypertension has been commonly documented too. The management of hypertension and its complications are common medical problems confronting the family physician. Improving the awareness level of patients on prehypertension and motivating patients towards adoption of healthy behavioural lifestyle changes are capable of halting progression from prehypertension to hypertension or even preventing it. The implication is that the scarce resources spent on antihypertensive drugs annually and the associated cardiovascular morbidity and mortality would be less. Furthermore, the doctor–patient ratio which is a critical factor related to quality healthcare delivery in sub-Saharan Africa would be positively impacted on as fewer patients with hypertension or its complications will present to the family physician for work-up. This has the potential of optimizing healthcare as the work load of family physicians would reduce and more time given to patients and their families for counselling and education.

1.3       AIM AND OBJECTIVES OF THE STUDY

 

AIM

The main aim of this study was to determine the prevalence and determinants of prehypertension in adult patients attending the General Outpatient Clinic (GOPC) of the Federal Medical Centre, Owerri, in order to reduce the incidence of hypertension-related cardiovascular morbidity and mortality.

 

OBJECTIVES

Specifically, the study sought to:

  1. Estimate the prevalence of prehypertension in adult patients (aged 18 years and above) in the study population.
  2. Determine the correlates of prehypertension in the study population

PREVALENCE AND DETERMINANTS OF PREHYPERTENSION AMONG ADULT PATIENTS ATTENDING THE GENERAL OUTPATIENT CLINIC OF THE FEDERAL MEDICAL CENTRE, OWERRI, IMO STATE

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