CHAPTER 2

LITERATURE REVIEWS

In this chapter, the researcher reviews concepts related to hypertension,

health behaviors, and the factors relating health behaviors. The information was

presented as follows:

1. Overview of hypertension

2. Health behaviors of patients with hypertension

3. Health behaviors of Vietnamese patients with hypertension

4. Social cognitive theory

5. Factors related to health behaviors of patients with hypertension

Overview of hypertension

In this part, the definition, types, classification, pathophysiology,

complications, hypertension among Vietnamese people, Vietnamese national policy

for hypertension, and management of hypertension were presented.

Definition of hypertension

In order to understand about hypertension or high blood pressure, it is very

important to understand what blood pressure (BP) is. It could be said that, blood is

carried from the heart to all parts of the body in blood vessels. Each time the heart

beats, it pumps blood into the vessels. BP is created by the force of blood pushing

against the walls of blood vessels (arteries) as it is pumped by the heart (WHO, 2013).

There are many definitions of hypertension in the literature. However, the definitions

were proposed by (JNC VII, 2003) and WHO are two popular definitions that are

being used.

According to WHO (2013), hypertension was defined as a systolic BP equal

to or above 140 mmHg and/ or diastolic BP equal to or above 90 mmHg. JNC VII has

proposed another definition of hypertension. This definition might clearer than the

definition of WHO because of the classification of BP. According to JNC VII,

hypertension was defined as systolic BP level of ≥ 140 mmHg and diastolic BP of ≥ 90

mmHg. The JNC VII defined normal BP as a systolic BP < 120 mmHg and diastolic

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BP < 80mmHg. The area between systolic BP of 120-139 mmHg and diastolic BP of

80-89 mmHg is defined as “prehypertension” (JNC VII, 2003).

It is important to note that the diagnosis of hypertension bases on the average

of two or more properly measured seated, BP readings on each of two or more office

visits (JNC VII, 2003).

Type of hypertension

Hypertension is generally divided into two main categories including

primary (Essential) hypertension and secondary hypertension.

1. Primary (essential) hypertension

Primary hypertension is the most prevalent type, affecting between 90-95

percent of patients diagnosed with hypertension. Primary hypertension does not have a

clearly identifiable known etiology. This differentiates primary from secondary

hypertension, in which blood pressure elevation occurs secondarily to another

identifiable cause (Eckman & Kirk, 2013). Although primary hypertension is

unidentifiable cause, however, the risk factors of primary hypertension have been

found in the literatures. Many studies have indicated several risk factors of primary

hypertension, such as age, body mass index (BMI), smoking and alcohol consumption

(Agrawal, Bhalwar, & Basannar, 2008; Bani, 2011; Chataut, Adhikari, & Sinha,

2011).

2. Secondary hypertension

The remaining 5-10 percent of hypertension cases is classified as secondary

hypertension. Secondary hypertension results from the identifiable cause. The cause

may be a specific pathophysiology or condition that result in hypertension, or the

development of high BP may be the result of the ingestion or certain drugs, food or

chemical (Eckman & Kirk, 2013).

Stages of hypertension

According to JNC VII (2003), BP has classified into three stages including:

normal, prehypertension, and hypertension.

Normal: Systolic BP less than 120 mmHg or diastolic BP ≤ 80 mmHg.

Pre-hypertension: Systolic BP is from 120 to 139 mmHg or diastolic BP is

from 80 to 89 mmHg.

Hypertension: this stage is classified into 2 categories as follows:

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Stage 1 hypertension: Systolic BP is from 140 to 159 mmHg or diastolic BP

is from 90 to 99 mmHg.

Stage 2 hypertension: Systolic BP is ≥ 160 mmHg or diastolic BP is ≥ 100

mmHg

It is importance to note that, JNC VII has introduced a term “Prehypertension”.

This term is used to classify people who have systolic BP ranging in about 120-139

mmHg and/ or diastolic BP ranging in about 80-89 mmHg. The goal of new

classification is intended to identify people who have high risk to be hypertension.

The identification of prehypertension will help healthcare providers to give early

intervention by using healthy lifestyle (JNC VII, 2003).

Pathophysiology of hypertension

In the present study, pathophysiology mechanisms of hypertension are

focused on primary hypertension. The mechanisms are as follows:

1. Genetic factor

Each person’s variance in BP is under an important degree of genetic

control, but quantitative estimates range from 35% to 70%. About 50% of patients

with hypertension have a family history of high BP or premature death from cardiac

problems in first degree relatives. People with normal BP but a strong family history

of hypertension are at a greater risk than those with no such history. The precise

identification of “genes that cause hypertension” has not been clear, however, because

of the multifactorial nature of the disease and the presence of many major pathogenetic

pathways. Indeed, major genes that definitely cause primary hypertension have yet to

be discovered, although more than 20 published genome wide screens are available

for genes that control BP. Some autosomal dominant genetically inherited forms of

hypertension exist, but they are very rare (Beevers, Lip, & O’Brien, 2007).

1. Balance between cardiac output and peripheral resistance

Blood pressure is normally dependent on the balance between cardiac output

and peripheral resistance. Cardiac output is the volume of blood flowing through

either the systemic or pulmonary circuit per minute. Cardiac output of the heart can be

changed by alteration in heart rate, stroke volume (Volume of blood ejected during

each ventricular contraction) or both. An increase in cardiac output without a decrease

in peripheral resistance will cause both arterial volume and arterial pressure to increase

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(Huether & McCance, 2012).

Total peripheral resistance is determined by changes in the diameter of the

arterioles. Arteriolar constriction increase mean arterial pressure by preventing the

free flow blood into the capillaries. Dilation has the opposite effect (Huether &

McCance, 2012).

Most patients with essential hypertension have increased peripheral vascular

resistance and a normal cardiac output. The cardiac output may be increased in the

early stages of essential hypertension, so that the peripheral resistance gradually

increases in order to maintain normal tissue perfusion and cardiac output returns to

normal. In the end stages of hypertension, left ventricular damage becomes so severe

that cardiac output decreases, so that BP is maintained solely by increased peripheral

vascular resistance. At the final stage, the cardiac output may be so impaired that BP

then decreases, rendering the patient frankly hypotensive (Beevers et al., 2007).

3. Renin-angiotensin-aldosterone system

Renin is secreted from the juxtaglomerular apparatus of the kidney in

response to glomerular underperfusion, reduced intake of salt, or stimulation from the

sympathetic nervous system. Renin results in the conversion of renin substrate

(Angiotensinogen) to angiotensin I, which is a physiologically inactive substance. A

key enzyme, angiotensin converting enzyme (ACE), results in the conversion of

angiotensin I to angiotensin II (Beevers et al., 2007).

Angiotensin II is a potent vasoconstrictor that leads to an increase in BP.

Angiotensin II may also cause some of the manifestations of hypertensive target organ

damage, such as left ventricular hypertrophy and atherosclerotic vascular disease.

Hypertension that results directly from excess renin and aldosterone is seen in patients

with renin secreting tumors and in some cases of renal artery stenosis. Angiotensin II

also stimulates release of aldosterone from the zonaglomerulosa of the adrenal gland.

Aldosterone causes fluid and sodium retention, and these results in a further increase

in BP (Beevers et al., 2007).

The renin-angiotensin system, however, is not thought to be responsible

directly for the increase in BP in patients with essential hypertension. Many patients

with hypertension have low levels of circulating endocrine renin and angiotensin II,

and, in these patients, the drugs that block the renin-angiotensin-aldosterone system

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tend to be less effective (Beevers et al., 2007).

4. Autonomic nervous system

The autonomic nervous system thus has an important role in maintaining a

“normal” BP, including the physiological responses to changes in posture, as well as

physical and emotional activity (Beevers et al., 2007).

Stimulation of the sympathetic nervous system can cause arteriolar

constriction and arteriolar dilatation. After stress and physical exercise, such changes

mediate short term changes in BP (Beevers et al., 2007).

Complications of hypertension

It is dangerous to ignore high BP, because this increases the chances of life-

threatening complications. The higher the BP is the higher the likelihood of harmful

consequences to the heart and blood vessels in major organs such as the heart, brain,

kidney, and eyes. This is known as cardiovascular risk, and can also be high in people

with mild hypertension in combination with other risk factors e.g., tobacco use, physical

inactivity, unhealthy diet, obesity, diabetes, high cholesterol, low socioeconomic

status and family history of hypertension (WHO, 2013).

1. Cardiovascular complications of hypertension

Cardiovascular complications of sustained hypertension include left ventricular

hypertrophy, angina pectoris, heart failure, coronary artery disease, myocardial

infraction, and sudden death. Myocardial hypertrophy in response to hypertension is

mediated by several neurohormonal substances. Hypertrophy is characterized by

changes in the myocyte protein, apoptosis of myocytes, and deposition of collagen in

heart muscle, which cause it to become thickened, scarred, and less able to relax

during diastole, leading to diastolic heart failure. In addition, the increased size of

heart muscle increase for oxygen delivery over time, the contractility of the heart is

impaired, and the individual is at increased risk for systolic heart failure (Huether &

McCance, 2012).

Vascular complications include the formation, dissection, and rupture of

aneurysm (outpouchings in vessel wall) and atherosclerosis leading to vessel occlusion

(Huether & McCance, 2012). Hypertension itself is directly harmful to the arterial

system, but it also act in concert with the other risk factors associated with the

development and acceleration of atherosclerosis. Atherosclerosis is the underlying

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pathophysiologic basis of coronary artery disease. The increased tension that

hypertension generates on the wall of arteries precipitates an increase in the

accumulation of collagen as well as reduction, fragmentation, and breakage of elastin

fibers. An ongoing low level of inflammation occurs in arteries exposed to hypertension,

and combined with the dyslipidemia commonly seen, the development of

atherosclerotic plaque is escalated (Eckman & Kirk, 2013).

2. Cerebral complications of hypertension

Hypertension and the accelerated development of atherosclerosis affect

arteries of all size throughout the body. Decreased flow or ruptured of weakened

blood vessels within the brain result in stroke. Ischemic stroke is associated with

atherosclerosis, whereas hypertension is a major risk factor for hemorrhagic stroke.

This type of stroke results in high mortality and morbidity (Eckman & Kirk, 2013).

3. Renal complications of hypertension

Renal complications of hypertension include parenchymal damage,

nephrosclerosis, renal arteriosclerosis, and renal insufficiency or failure.

Microalbuminuria (small amount of protein in the urine) occurs 10% - 25% of

individuals with primary hypertension and is now recognized as an early sign of

impending renal dysfunction and significantly increased risk for cardiovascular

events, especially in those who have diabetes (Huether & McCance, 2012).

The atherosclerosis with coronary artery disease is likely to be the basis for

the damage to the microcirculation of the kidneys that develops with chronic

hypertension. Within a proscribed mean arterial pressure, healthy kidneys are able to

auto-regulate blood flow delivered to the glomerulus, but with prolonged or severe

hypertension this regulatory mechanism is lost and glomerular damage ensues.

Damage to glomerulus allows large molecules not normally filtered out of the

bloodstream to appear in urine. The presence of microalbuminuria (Proteinuria) is

reflective of increased glomerular permeability and an early indicator of hypertensive

renal injury. At this point, the patient is usually asymptomatic, but if interventions for

blood pressure control are not initiated, renal impairment progresses, culminating in

end-stage of renal disease, which require long-term renal dialysis or transplantation

(Eckman & Kirk, 2013).

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4. Retinal complications of hypertension

The characteristic retinal changes include arteriolar narrowing, arteriovenous

crossing changes, alteration of light reflexes on arterioles, cotton-wool spot,

microaneurisms, retinal hemorrhage, retinal edema, and blurred disc margin

(Gunderson & Karnath, 2003).

In addition, identifiable damage to the kidneys is often preceded by changes

in the microcirculation of the eyes. Atherosclerosis also contributes to the retinal

injury produced by hypertension. The result may be retinal detachment or

hemorrhage, which can cause blindness (Eckman & Kirk, 2013).

Management of hypertension

JNC VII (2003) has recommended the management of hypertension. It was

proposed that management of hypertension includes pharmacological and non-

pharmacological management.

Pharmacology management

Not all patients diagnosed with hypertension require medication, but those at

medium to high risk will need one or more of essential medicines to lower their cardio

vascular risk (WHO, 2013). More than two-thirds of hypertensive individuals cannot

be controlled on one drug and will require two or more antihypertensive agents

selected from different drug classes (JNC VII, 2003).

The antihypertensive drugs are commonly used to treat hypertension that

will be mentioned as follows:

Thiazide diuretics: Thiazide diuretics are cheap, easy to use, and can be

given once daily. They are effective and are the drugs of choice in elderly people. The

thiazides reduce blood pressure by increasing excretion of sodium and water, which

lowers blood volume, but they also have some vasodilating properties. The reduction

in blood volume results in reflex activation of the renin-angiotensin-aldosterone

system, which leads to an increase in peripheral vascular resistance that may attenuate

the reduction of BP (Beevers et al., 2007).

Beta Blocker: Most beta blockers reduce cardiac output through negative

chronotropic and inotropic effects. The short term hemodynamic responses are partly

offset by reflex activation of vasoconstrictor mechanisms, which may attenuate

reductions in BP. Release of renin from the kidneys is also partly blocked. As with the

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thiazide diuretics, the beta blockers have a relatively flat dose-response curve for

reductions in BP. As their mechanism of action involves suppression of renin, they

tend to be less effective than monotherapy in elderly people and African-Caribbeans,

although this can be overcome with concomitant use of diuretics (Beevers et al., 2007).

Calcium channel blockers:Calcium channel blockers act by inhibiting the

transfer of calcium ions across smooth muscle cell membranes, which produces

arteriolar vasodilatation. The systolic hypertension in Europe trial and two other long

term outcome trials validated their use as first line drugs in patients with hypertension.

Calcium channel blockers are useful antianginal and antihypertensive drugs. Non-

dihydropyridine calcium channel blockers (Diltiazem and verapamil) block calcium

channels in cardiac myocytes. This reduces cardiac output and may have some

antiarrhythmic action on the atrioventricular node. The dihydropyridine calcium

channel blockers (Such as nifedipine, amlodipine, and felodipine) block L type

calcium channels in vascular smooth muscle cells. This causes vasodilatation and

reductions in vascular resistance and arterial blood pressures. These agents have little

effect on the atrioventricular node but do have some mild diuretic effects (Beevers et

al., 2007).

Angiotensin converting enzyme inhibitors: The angiotensin converting

enzyme inhibitors are a major class of drugs that has transformed the treatment of

cardiovascular disease. As the name implies, these drugs block angiotensin converting

enzyme, which converts angiotensin I to angiotensin II, mainly in the lungs. Angiotensin

II is a potent vasoconstrictor and also stimulates aldosterone release from the adrenal

cortex, which causes retention of sodium and water. The angiotensin converting

enzyme inhibitors thus cause vasodilatation and, to a lesser extent, reduced renal

absorption of sodium and water. In addition, angiotensin II has many other properties

that may be harmful in vascular disease, and its inhibition (At the local tissue and

systemic levels) leads to additional benefits. Angiotensin converting enzyme is also

responsible for the breakdown of bradykinin, and angiotensin converting enzyme

inhibitors increase levels of bradykinin, which enhances vasodilatation (Beevers et al.,

2007).

Angiotensin receptor blockers:The angiotensin receptor blockers block type

I angiotensin II receptors (AT1), which leads to vasodilatation and reductions in BP

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(Beevers et al., 2007).

Alpha blocker: The alpha blockers block the activation of alpha-1

adrenoceptors in the vascular tree, which results in vasodilatation. Alpha Blockers are

considered to be third or fourth line drugs for hypertension and should be used with

caution in patients at risk of heart failure (Beevers et al., 2007).

The way of taking antihypertensive medications and effect of taking

antihypertensive medications on blood pressure and blood pressure control will be

mentioned in the part of self-care behaviors of patients with hypertension in this

chapter.

Non-pharmacology management

JNC VII (2003) proposed that non-pharmacology management in

hypertension can be considered as healthy lifestyles which hypertensive patients adopt

in order to prevent and manage the hypertensive condition. JNC VII (2003) also

indicated that adoption of healthy lifestyles by all persons is critical for the prevention

of high BP and is an indispensable part of the management of those with hypertension.

According to JNC VII (2003) non-pharmacology considerations for hypertensive

patients include diet, weight management, physical activity, limiting alcohol

consumption, and smoking cessation. The detail information of non-pharmacology

considerations will be presented in part of health behaviors of patients with

hypertension in this chapter.

Hypertension among Vietnamese people

The prevalence of hypertension in Vietnam is high. It is estimated that the

overall prevalence of hypertension was 25.1% in men and 23.1% in women (Vietnam

National Heart Institute, 2008). Moreover, the rate of hypertension among adults

increased rapidly. It was 1% in 1960 in Northern Vietnam and increased to 23.1% in

2001 (Khan & Khoi, 2008). Regarding to Thai Nguyen province, Thai Nguyen is a

province that locate in the north of Vietnam. The population of this province was

estimated about 1,131,000 residents. It was estimated that the prevalence of

hypertension in Thai Nguyen province was 23% of population (Ha et al., 2013).

After reviewing the literature, the researcher found that the prevalence of

hypertension in Vietnam is different in term of region, age, and gender. According to

Thuan (2006) the prevalence of hypertension in Ho Chi Minh City (A city in south of

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Vietnam) was 21.9% of the overall population. Whereas, the prevalence of

hypertension in Hue City (A city in middle of Vietnam) was 36% (An & Lan, 2005),

and it was 23% of population in Thai Nguyen province (a province located in the

north of Vietnam) (Ha et al., 2013). In term of age, it was found that older people have

higher prevalence of hypertension than younger people. The study of Ha et al. (2013)

found that the prevalence of hypertension was higher in older individuals (≥ 45 years

old). Another study was conducted by Minh and Phung (2010) in KhanhHoa province.

The result of their study showed that the prevalence of hypertension among elderly

population (≥ 60 years old) in KhanhHoa province was high (48.1%). In regard to

gender, it was found that the prevalence of hypertension in male is higher than female.

In a study of 2,000 adults, the result indicated that the prevalence of hypertension in

male was higher than female subjects, in which the prevalence of hypertension was

found as 18.1% in male, and 10.1% in female (Minh, Byass, Chuc, & Wall, 2006).

The higher prevalence of hypertension in males as compared with females among

Vietnamese hypertensive patients has been found in other studies (Ha et al., 2013;

Minh & Phung, 2010).

Vietnamese national policy for hypertension

In the past, hypertension management program focused more on treating

hypertensive patients, who might already have experienced complications such as

stroke, acute myocardial infarction or heart failure in hospitals, and gave less attention

to prevention in the general population. Early in 2008, with responsibility as the

leading national institute for preventing and controlling cardiovascular diseases and

based on previous studies as well as the international guidelines and experience,

Vietnam National Heart Institute developed a national targeted hypertension

management program in response to the current burden of hypertension and submitted

a strategy to the Ministry of Health and Government. In December 2008, the

Vietnamese Prime Minister issued Decision No. 172/ 2008/ QD-TTg on the Approval

of the National Targeted Program for Hypertension Prevention and Control which

provided preventive community interventions. The goal of the programwas both to

control the incidence of new cases of hypertension, resulting in fewer new cases, and

to reduce its prevalence, so that individuals were not exposed to the deleterious effects

of high blood pressure for extended periods of time. The national program included

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education and training to improve the skills of health professionals and medical staff,

especially at primary health care or commune health station levels, to deliver healthy

lifestyle advice to hypertensive people as well as to the general population.The

program is in the process of undertaking, and the effect of this program on

hypertension are being evaluating.

Health behaviors of patients with hypertension

Health behaviors refer to behavior patterns, actions, and habits that relate to

health maintenance, to health restoration, and to health improvement (Gochman, 1997).

In addition, health behavior is a key strategy to manage illness and enhance quality of

life among chronic illness patients such as hypertension (JNC VII, 2003; WHO,

2013). The benefits of health behaviors for clinical outcome of chronic disease have

been widely found in the literature (Alaska Section of Chronic Disease Prevention and

Health Promotion, 2013; Garrett & Bluml, 2005). Health behaviors for hypertensive

patients suggested by JNC VII (2003) include taking medication as prescribed, weight

management, healthy diet, physical activity, smoking cessation, and limiting alcohol

consumption.

Taking medication

In order to support hypertensive patients in controlling blood pressure,

adherence with antihypertensive medications or taking medication as prescribed is a

crucial (JNC VII, 2003; WHO, 2013). According to WHO (2003) adherence was

defined as the extent to which a person’s behaviors (Taking medication, following a

diet, and/or executing lifestyle changes) corresponds with agreed recommendations

from a health care provider. In this part the researcher focuses on adherence with

taking antihypertensive medications. The report of WHO (2003) about adherence with

long term therapy pointed out that patients are considered to be adherent with taking

medication when they taking medication appropriately. It could be said that patients

need to take medications that coincide with healthcare provider’s advices (Taking the

prescribed number of pills each day, and taking pills within a prescribed period), even

after the blood pressure is lowered patients still need to take medicine.

Each kind of antihypertensive medication has its own mechanism that

influences on blood pressure. Medications influence blood pressure by increasing

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excretion of sodium and water; reduce cardiac output, or inhibiting the transfer of

calcium ions across smooth muscle cell membranes. The mechanisms of

antihypertensive medications influence blood pressure were mentioned in the part of

pharmacological management in this chapter.

The effect of taking medication on blood pressure and blood pressure control

was found in the literature. According to WHO (2013) good adherence with taking

medication has been associated with improved BP control and reduced complications

of hypertension. In addition, Ramli, Ahmad, and Paraidathathu (2012) have conducted

the study that investigates the relationship between medication adherence and

controlled BP among hypertensive patient. The result of their study indicated that poor

medication adherence was found to negatively affect BP control.

Diet

DASH eating plan is widely known as an effective diet which was

recommended for hypertensive patients to adopt in order to control blood pressure.

DASH eating plan is a diet rich in fruits, vegetables, and low fat dairy products with a

reduced content of dietary cholesterol as well as saturated and total fat (modification

of whole diet). It is rich in potassium and calcium content. In addition, nearby DASH

eating plan, low sodium intake diet was also recommended for hypertensive patients

(JNC VII, 2003).

National Heart, Lung, and Blood Institute [NHLBI] (2006) proposed the

DASH eating plan for hypertensive patients as follows:

Grain and grain products: 6-8 daily serving

Vegetables: 4-5 daily serving

Fruit: 4-5 daily serving

Fat-free or low-fat, milk and milk products: 2-3 daily serving

Lean meats, poultry, and fish: 6 or less daily serving

Nuts, seeds, and legumes: 4-5 serving per week

Fats and oils: 2-3 daily serving

Sweet and added sugars: 5 or less serving per week

For low sodium intake diet, JNC VII (2003) recommended that hypertensive

patient should reduce sodium intake to no more than 100 mmol (2.4 g of sodium) per

day.

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The effect of DASH eating plan and low sodium intake diet were found in

the literature. The randomized control trial that was conducted on 116 patients, the

result of this study found that DASH eating plan could reduce systolic blood pressure

(12 and 11mmHg), and diastolic blood pressure (6 and 7mmH) among men and

women respectively (Azadbakht, Mirmiran, Esmaillzade, Azizi, & Azizi, 2005). In

addition, hypertensive patients who reduce dietary sodium intake to no more than 100

mmol per day (2.4 g sodium or 6 g sodium chloride) that can reduce blood pressure

from 2 to 8 mmHg (JNC VII, 2003). Moreover, the study that was conducted by

Kojuri and Rahimi (2007) indicated that no added salt diet can significantly reduce

systolic and diastolic BP during the day (12.1/ 6.8 mmHg) and night (11.1/ 5.9

mmHg).

Weight management

According to JNC VII (2003) maintaining normal body mass index (18.5-

24.9 kg/ m2) which help hypertensive patients to control blood pressure. Moreover,

systolic blood pressure can be reduced between 5-10 mmHg for every 10 kg of body

weight that is lost. Additionally, the significant effect of weight management on

reduce BP has found in the literature (Bacon, Sherwood, Hinderliter, & Blumenthal,

2004; Blumenthal et al., 2000). In contrast, overweight and obesity were found to be

strong risk factors for hypertension and uncontrolled blood pressure in hypertensive

patients. According to Kotsis et al. (2005) there was an increase in the incidence of

hypertension in overweight and obese subjects compared with normal weight subjects,

this study was also found that excess weight gain is a consistent predictor for subsequent

development of essential hypertension. In addition, the study of Cordero et al. (2011)

found that uncontrolled blood pressure was more frequently in overweight and obese

patients.

Hypertensive patients can manage their weight by checking their BMI or

waist circumference. In hypertensive patients who need to lose weight, it’s important

to do so slowly; lose no more than 1/ 2 pound to 2 pounds per week and begin with a

goal of losing 10 percent of your current weight. This is the healthiest way to lose

weight and offers the best chance of long-term success (NHLBI, 2003). Physical

activity and diet can help hypertensive patient to lose weight. NHLBI (2003) suggested

that hypertensive patients who want to lose their weight can adopt DASH eating plan,

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but follow it at a lower calorie level (Patients can make it lower in calories by

replacing high-calorie foods with more fruits and vegetables).

In fact, the mechanism of hypertension induced by overweight and obesity is

not well understood. However, it could be said that obesity might lead to hypertension

and cardiovascular disease by activating the renin–angiotensin–aldosterone system, by

increasing sympathetic activity, by promoting insulin resistance and leptin resistance,

by increased pro-coagulatory activity and by endothelial dysfunction. Further

mechanisms include increased renal sodium reabsorption, causing a shift of the

pressure-natriuresis relationship and resulting in volume expansion (Wofford & Hall,

2004).

Physical activity

JNC VII (2003) recommended that hypertensive patients who are able

should engage in regular aerobic physical activity at least 30 minutes per day and most

days of the week. According to NHLBI (2006) aerobic physical activity refers to any

physical activity that uses large muscle groups and causes your body to use more

oxygen than it would while resting. Aerobic activity is the type of movement that

most benefits the heart. Examples of aerobic activity are brisk walking, jogging, and

bicycling.

The linkage between physical activity and blood pressure can be explained

by burning of calories. Physical activity benefits for blood pressure by burning extra

calories, which can help hypertensive patients to lose excess weight or stay at healthy

weight (NHLBI, 2006) thereby contributing to blood pressure control in hypertensive

patients.

The effect of physical activity on BP was widely found in the literature. The

randomized control trial which was conducted by Lee and colleagues showed that

patients who follow physical activities’ recommendation can decrease 15.4 mmHg of

systolic BP (Lee et al., 2007). In addition, robust statistically significant effects were

found for improved aerobic exercise: mean reductions in systolic BP of 4.6 mmHg

with corresponding reductions in diastolic BP (Dickinson et al., 2006). Moreover,

hypertensive patients who engage in physical activity more than 3 day per week were

more likely to control blood pressure than hypertensive patients who did not (Alsairafi

et al., 2010).

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Limiting alcohol consumption

According to JNC VII (2003) hypertensive patients should limit alcohol

consumption to no more than 1 oz (30 mL) of ethanol, the equivalent of two drinks

per day in most men and no more than 0.5 oz (15mL) of ethanol (One drink) per day

in women and lighter weight persons. A drink is 12 oz of beer, 5 oz of wine, and 1.5

oz of 80 proof liquor. The study of Whelton et al. (2002) found that modest

consumption of alcohol (e.g., < 30 grams of ethanol a day or approximately two

“drinks” daily) is not generally associated with BP increases. Larger amounts of

alcohol ingestion have a dose related effect on BP, both in hypertensive and

normotensive subjects. Additionally, high intake of alcohol can be related to

hypertension, as well as obesity and other problems, including cardiac arrhythmias,

alcoholic cardiomyopathy, neuropathy, liver disease, and pancreatitis. In patients with

hypertension, even a moderately high intake of alcohol of 80 g/ day (Equivalent to

four pints of beer a day) can significantly increase blood pressure. Binge drinking has

been associated with an increased risk of stroke (Beevers et al., 2007).

The mechanisms of alcohol’s effect on BP are unclear but appear

predominantly to result from sympathetic neural activation, although changes in

cortisol and cellular calcium concentrations also may play a role (JNC VII, 2003).

The effect of limiting alcohol consumption on blood pressure was found in

the literature. The study of Dickinson et al. (2006) found that limiting alcohol

consumption can reduce systolic blood pressure of 4.6 mmHg with corresponding

reductions in diastolic blood pressure. In addition, limiting consumption to no more

than 2 drinks (e.g., 24 oz beer, 10 oz wine, or 3 oz 80-proof whiskey) per day in most

men, and to no more than 1 drink per day in women and lighter weight persons can

decrease blood pressure by 2-4 mmHg in hypertensive patients (Xin et al., 2001).

Smoking cessation

According to JNC VII (2003) for overall cardiovascular risk reduction,

patients should be strongly counseled to quit smoking. In addition, chronic and heavy

cigarette smoking may be associated with hypertension. Indeed, BP can increase

acutely during smoking. Importantly, smoking has a graded adverse effect on

cardiovascular risk, increasing it even more than mild hypertension. People who stop

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smoking rapidly reduce their risk by as much as 50% after one year (Beevers et al.,

2007).

In fact, inhaling tobacco smoke causes several immediate responses within

the heart and its blood vessels. Within one minute of starting to smoke, the heart rate

begins to rise. This is partially attributable to nicotine, the addictive substance in

cigarettes. Nicotine stimulates the body to produce adrenaline, making the heart beat

faster. Nicotine also increases blood pressure (Primatesta, Falaschetti, Gupta, Marmot,

& Poulster, 2001).

Health behaviors of Vietnamese patients with hypertension

Studies showed that Vietnamese patients with hypertension did not do well

in health behaviors as recommended. Regarding dietary habits, the study of 300

hypertensive patients found that the prevalence of eating salty food among hypertensive

patients was still high. The result of the study found that 81% of hypertensive patients

ate salty food (Phong & Hai, 2010). In addition, the study of Phuong et al. (2006)

found that there are only 34.8% of hypertensive patients who followed eating

recommendation for hypertensive patients.

In term of weight management, the study on 1250 participants showed that

approximately 40% of hypertensive patients were obese (Phuong et al., 2006). In

addition, according to Nguyen et al. (2012), during 2001 to 2009 the BMI of

Vietnamese population significantly increased. It is one of reasons which leaded to

increase the prevalence of hypertension among Vietnamese population.

Regarding physical activity, the study of Phuong et al. (2006) indicated that

among hypertensive patients there were only 42.6% of hypertensive patients who

exercise regularly. In other study that was conducted by Phong and Hai (2010), the

result showed that among hypertensive patients there was only 40% who engaged in

physical activity.

After reviewing the literature, the researcher found that the rate of patients

who smoke and drink alcohol was still high among Vietnamese hypertensive patients.

The study of Phuong et al. (2006) found that the prevalence of hypertensive patients

who smoke in this study was 56%. The high prevalence of smoking was also found in

another study. In the study of Phong and Hai (2010), the result showed that the

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prevalence of hypertensive patients who smoke was 35%. In addition, the result of this

study also indicated the high prevalence of alcohol consumption among hypertensive

patients (55%).

The evidences above indicated that there were limited studies that investigated

about health behaviors among hypertensive patients. In addition, the prevalence of

performing health behaviors among hypertensive patients in Vietnam was

unacceptably low. The situation indicated the need to conduct further study that

examines health behaviors and predictors of health behaviors among Vietnamese

hypertensive patients.

Social Cognitive Theory [SCT]

SCT proposed that human behaviors, specific health behaviors are

influenced by personal factors (including cognitive, affective, biological, and other

personal factors), and environmental factor (Bandura, 1997). According to this theory,

cognitive factor and other personal factors regulate human behaviors, while

environmental factors may facilitate or impede an individual to perform his/ her

specific behavior.

In SCT, a personal factor refers to cognitive, affective, biological properties,

and other personal factors. Cognition refers to what people think and believe

(Bandura, 1989). The person’s belief can affect thought patterns and thereby can

enhance or undermine the performance of behaviors. In addition, SCT posited that

affective states can influence person’s behaviors. Affection refers to what people feel.

Bandura proposed that person’s feeling can affect thought patterns and thereby can

enhance or undermine the performance of behaviors (Bandura, 1989). The personal

factor also encompasses the biological properties. Biological properties refer to

gender, ethnicity, temperament, and genetic predisposition, Bandura proposed that

biological properties can affect human behavior and impose constraints on human

capabilities (Bandura 1989). Another personal factor in SCT is physical states. It

refers to physical accomplishments, and health condition. Physical states influence

human behavior (Bandura, 1997).

Environmental factors can facilitate or impede individuals to perform

specific behaviors (Bandura, 1989). Environments are of all the factors that physically

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external to that person or person’s cognitive or mental representation of environments

(.e.g. provision of social support).

Previous studies have used SCT as framework to explore human, and health

behaviors. In term of hypertension, several studies have also used SCT as framework

of those studies to explore related factors and influence factors of health behaviors

(Lee et al., 2010; Yang et al., 2013).

Factors related to health behaviors of patients with hypertension

Studies about health behaviors have used social cognitive theory to explain

the relationship among related factors and health behaviors. In the present study, the

variables of interest were guided from social cognitive theory. In addition, previous

studies also showed the evidences supporting the relationship among these studied

variables including gender, duration of hypertension, perceived self-efficacy,

emotional well-being, and perceived social support and health behaviors of patients

with hypertension (Hu et al., 2013; Lee et al., 2010; Pinprapapan et al., 2013; Trivedi

et al., 2008; Warren-Findlow et al., 2012). Discussions on these variables were

presented as follows:

Gender

Gender belongs to concept of biological properties in personal factors within

SCT. Bandura posited that personal factors can influence human behaviors (health

behaviors) by affecting human thought and belief (Bandura, 1997). In addition, Yang

et al. (2008) indicated that social and cultural factors may encourage female to engage

in health behaviors (No smoking, and limiting alcohol consumption). The relationship

between gender and health was found in the literature, however it is still inconclusive.

The study of Lee et al. (2010) that explored correlated factors of health behaviors on

445 hypertensive patients found that female gender was significantly correlated with

higher levels of hypertension health behaviors (r = .134, p ≤ .01). The significant

relationship between gender and health behaviors was also found in another study that

was conducted by Warren-Findlow et al. (2012). In this study, femalehypertensive

patientswere more likely to engage in adherence to hypertensive medications more

than male (OR = 1.51, 95% CI: 1.10-1.85) and female gender was statistically

significantly associated with higher prevalence of adherence to low salt diet

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techniques. However the study on 250 hypertensive patients in Iran found that there

was no significant association between gender and adherence to hypertensive

medication (Hadi & Rostami-Gooran, 2004). In addition, the study of Trivedi et al.

(2008) found that female gender was associated with greater reported adherence to

medications (OR = 1.503, p < .05) and non-smoking status (OR = .504, p < .01).

These findings were consistent with the result of other studies (Hu et al., 2013; Ross et

al., 2004). However, in other study that was conducted on 1369 hypertensive

participants showed that gender did not associate withhealth behaviors in patient with

hypertension (Heymann et al., 2011). The inconsistent result among studies indicated

that gender is still questionable whether or not it is a related factor of health behaviors

among hypertensive patients.

Duration of hypertension

Duration of hypertension refers to amount of months that any patient is

diagnosed with hypertension. It belongs to concept of physical states in personal

factors within SCT. Bandura posited that personal factors can influence human

behaviors (health behaviors) by affecting human thought and belief (Bandura, 1997).

In fact, duration of the disease can affect individual’s ability to perform health

behaviors because patients have more experiences and knowledge which facilitate

them to engage in health behaviors (Peter & Templin, 2008). A study on 306

hypertensive patients revealed that patients with longer history of hypertension had

significantly higher level of performing health behaviors (r = .19, p < .01) (Peter &

Templin, 2008). In addition, Lee et al. (2010) studied factors related to health

behaviors among Korean American hypertensive patients. The study showed that

duration of hypertension was found as a related factor of health behaviors in regard to

adherence to taking medication, diet, physical activity, and weight management (r =

.177, p ≤ .01).Another study was conducted on 318 hypertensive patients. The result

of that study found that participants who were diagnosed as hypertension for a long

period were more likely to have higher health behavior related to adherence to

hypertensive medication (OR = 3.44, 95% CI 1.99-5.97) (Hu et al., 2013). However,

the study of factors related to medication adherence among hypertensive patients in

Iran found that there was no significant difference among patients with differing

durations of hypertension (Hadi & Rostami-Gooran, 2004). Although duration of

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hypertension has found as anassociated factor for health behaviors in patient with

hypertension, however, the understanding about the relationship between duration of

hypertension and health behaviors in Vietnamese hypertensive patient that is still

limited.

Perceived self-efficacy

Perceived self-efficacy, a component of social cognitive theory (SCT), refers

to the confidence in ability to perform a specific behavior (Bandura, 1997). According

to SCT, people will perform and maintain their actions based on perceived self-efficacy.

A number of studies showed the relationship between perceived self-efficacy and

health behaviors in hypertensive patients.The study on 445 hypertensive patients

found thatperceived self-efficacy had positive relationship withhealth behaviors

relating to medication-taking, healthy diet, weight control, and exercise (r = .279,

p ≤ .001) (Lee et al., 2010). This finding was consistent with the study of Pinprapapan

and colleagues (2013). The authors have found that perceived self-efficacy had a

direct positive effect on adherence to health behaviors as recommended for Thai

hypertensive patients. In the study that investigates the effect of self-efficacy of

African-American adults with hypertension on health behaviors, the result of this

study found that individuals with good self-efficacy were more likely to had good

health behaviors practices in regard to adhering to low salt diet intake, engaging in

physical activity, not smoking, and following good weight management strategies

(Warren-Findlow et al., 2012).In addition, the study explored factors related to health

behaviors of 234 woman in South Korea found that perceived self-efficacy had

positive relationship with health behaviors (r = .609, p < .001) (Yang et al., 2013).

Although, self-efficacy is a major factor associated with health behaviors, however,

study on perceived self-efficacy has been mostly conducted in Western countries.

There are limited understandings about the relationship between perceived self-

efficacy andhealth behaviors among hypertensive patients in Vietnam. The situation

indicated the need to conduct the study that investigates the association between

perceived self-efficacy andhealth behaviors among hypertensive patients in Vietnam.

Emotional well-being

Emotional well-being was defined as a positive sense of well-being which

enables an individual to be able to function in society and meet the demands of

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everyday life (Mental Health Foundation, 2005). It belongs to concept of affection

within construct of personal factors in SCT. Theoretically, people’s affection,

specifically emotional well-being, has an influence on their actions or any change in

their behaviors (Bandura, 1997). Additionally, patients with chronic diseases have to

face with adhering to long term of treatment, and lifestyle modification. These

changes on lifestyle may affect emotion of chronic patients. As a result, they can

develop emotionally unhealthy problems which are caused by adherence with long

term conditions of chronic disease. Emotional unhealthiness may impair health

behaviors of chronic illness by adversely effecting memory, energy, and executive

function (Katon, 2003). Moreover, the sense of helplessness and hopelessness

associated with emotional unhealthiness may decrease motivation to care for chronic

illness (Katon, 2011). These evidences above indicated that emotional well-being can

be a related factor of health behaviors among patients with chronic diseases.

The impact of emotional well-being on health behaviors has found in chronic

diseases. A critical literature review that was conducted by Daly and colleagues

(2002) the result of their review indicated that emotionally healthy patients show

greater adherence to maintaining exercise among patients with heart disease. In the

context of diabetes, emotional well-being was also found to influence eating related

behaviors among diabetic patients (Alum, Sturt, Lall, & Winkley, 2008; Ismail,

Winkley, & Rabe-Hesketh, 2004).

The results of those studies above indicated that there are strong evidences in

other chronic illnesses that emotionally healthy patients show greater adherence to

health behaviors. In the context of hypertension, the relationship between emotional

well-being and health behaviors was found among hypertensive patients. The study of

Wang et al. (2002) showed that emotional well-being of hypertensive patients were

related to health behavior of adherence to medications. In addition, the study on 636

hypertensive patients found that patients who have higher level of emotional well-

being were significantly correlated with better adherence to medications (r = .16, p <

.001), better adherence to dietary recommendations (r = .18, p < .001), better

adherence to exercise recommendations (r = .18, p < .001) and lower incidence of

current smoking (r = -.16, p < .001) (Trivedi et al., 2008).

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Although, emotional well-being may be helpful to explain health behaviors

in hypertensive patients, however, in Vietnam, the psychological effect on health

behaviors is still paid less attention. In order to enhance the knowledge, benefit for

nursing practice, and enhance adherence to health behaviors for hypertensive patients,

emotional well-being should be study as a related factor of health behaviors of

Vietnamese hypertensive patients.

Perceived social support

Perceived social support refers to individual perceives support of attachment/

intimacy, social integration nurturance, reassurance of worth, and availability of

assistance (Weiss 1969, 1974 cited in Weinert, 2003). It belongs to the construct of

environmental factors within SCT. Bandura suggested that environmental factors can

facilitate or impede the performance of human behaviors (Health behaviors) (Bandura,

1997).In the context of managing chronic condition, perceived social support has

found to be a predictor of health behaviors among patients with chronic disease. In the

study of Cene et al. (2013) which was conducted on 150 heart failure patients, the

result of this study showed that perceived social support influence health behaviors in

patients with heart failure (β = .23, p = .04). The effect of perceived social support

was also found in other chronic diseases.

In term of hypertension, perceived social support was also found as an

associated factor for health behaviors in patients with hypertension. However, there is

inconsistent result among studies. The study on 321 hypertensive patients found that

perceived social support had a direct positive effect on adherence to health behaviors

in patient with hypertension (Pinprapapan et al., 2013). In addition, in the study that

was conducted by Ma et al. (2013) indicated that patients with higher level of

perceived social support were more likely to have higher level of health behaviors.

Moreover, Yang et al. (2013) also pointed out that perceived social support

significantly correlated with health behaviors in hypertensive patients (r = .407, p <

.001). Nevertheless, the studies of Lee et al. (2010) and Wang et al. (2002) found that

perceived social support did not have significant relationship with health behaviors in

hypertensive patients. The evidences above indicated that there were the inconclusive

results on whether or not perceived social support is a related factor of health

behaviors in patients with hypertension. Therefore, study in order to explore the

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relationship between perceived social support and health behaviors among

hypertensive patients should be examined.

Conclusion

In conclusion, from the literature review, the researcher has found that

hypertensive patients are less engaged in health behaviors. The literature reviews also

indicated that gender, duration of hypertension, perceived self-efficacy, emotional

well-being, and perceived social support had significant association withhealth

behaviors in patients with hypertension. However, there is still limited study in

Vietnamese patients with hypertension that explores the related factors of health

behaviors. Therefore, the better understanding of the relationship of those variable

andhealth behaviors that will help nurse actively intervene in order to enhance

patient’s ability to engage in health behaviors for Vietnamese hypertensive patients.