View
4
Download
0
Category
Preview:
Citation preview
CHAPTER 1
INTRODUCTION
Background and Significance of the Research Problem
Hypertension is an important public health problem which is a major cause
of death and disability in both developed and developing countries (He & MacGregor,
2007). Kearney et al. (2005) reported that overall 26.4 % of adult population in
different world regions in 2000 had hypertension and the estimated number of adults
with hypertension in 2025 would increase to 60%. In the United States data from the
National Health and Nutrition Examination Survey (NHANES) revealed that the
prevalence of hypertension among U.S. adults was approximately 30% in 2007-2008
(Yoon, Ostchega, & Louis, 2010). In Thailand, the data from the 4th
National Health
Examination Survey (NHES) during 2008-2009 showed that the prevalence of
hypertension was 21.4% (Aekplakorn, 2010). Additionally, the number of Thai
patients who were hospitalized with hypertension has been increasing dramatically
from 2008 to 2010. There were 494,809 patients in 2008 and it increased to 859,583
in 2010 (Bureau of Non Communicable Disease, Department of Disease Control,
Ministry of Public Health, 2013). This data confirms that hypertension is one of
major health problems in Thailand.
The target goal of therapy of hypertension is to control blood pressure to
optimal level (SBP < 140 and DBP < 90 mmHg) in order to prevent severe
complications. The 7th
Report of Joint National Committee (JNC-7) on Prevention,
2
Detection, Evaluation, and Treatment of High Blood Pressure proposed the treatment
guideline for hypertension including pharmacology and non-pharmacology
treatments. Hypertensive patients should take medication as prescribed and change
their lifestyles to control blood pressure (Chobanian et al., 2003). Taking
antihypertensive drugs decreases the risk of stroke by 30%, cardiovascular disease by
10-20% and heart failure by 40-50% (Psaty et al., 2003; Roberts & Small, 2002). A
systematic reviews of the experimental designs showed the average systolic blood
pressure decreased of 2.9 mmHg when sodium consumption was restricted to 100
mmol/day in patients with hypertension, 5.2 mmHg when weight was lost and 0.8
mmHg when doing exercise (Ebrahim & Smith, 1998). The combination of two or
more lifestyle modifications achieved more to control blood pressure than one
(Chobanian et al., 2003). For example, the randomized controlled trial study of
effects of combination lifestyles modification on blood pressure showed that
hypertensive patients who adopted a DASH diet and weight management (exercise 3
times per week) had lower systolic and diastolic blood pressure than those who
received only counseling on the DASH diet (Blumenthal et al., 2010). The
effectiveness of an antihypertensive drug and lifestyle modifications are treatments to
attain the goal blood pressure level for persons with hypertension, so they need to
adhere to both medication and adopt healthy lifestyle in order to control their blood
pressure.
Adherence to therapeutic regimens plays a key role to manage
hypertension. The term adherence is viewed as patients having an active role in their
treatment (Cohen, 2009; Shay, 2008). World Health Organization [WHO] (2003)
defined adherence to long term therapy as the extent to which a person’s behavior:
3
taking medication, following a diet, and/or executing lifestyle changes, corresponds
with agreed recommendations from the health care providers. Cohen (2009) defined
adherence as persistence in the practice and maintenance of desired health behaviors
and is the result of active participation and agreement and its attributes consist of
alignment of patient behaviors and health recommendations, mastery of a new
behaviors and health knowledge, ongoing collaboration relationship between the
patient and health care providers and their ability to meet the outcome targets. Thus
adherence to therapeutic regimens in persons with hypertension means that persons
with hypertension should agree with and perform recommended behaviors given by
health care providers including taking antihypertensive medications as prescription,
changing healthy lifestyles into their daily activities, collaboration with health care
providers to control their blood pressure and their ability to meet the outcome targets.
The benefits of adherence to therapeutic regimens among hypertensive
patients have clearly shown in many studies. DiMatteo, Giordani, Lepper, and
Croghan (2002) conducted a meta-analysis study on adherence in hypertensive
patients and found that patients who adhered to antihypertensive medication had a
3.44 times better chance of controlling blood pressure than those who were non-
adherent. Patients who adhered to prescribed medication had a lower level of systolic
blood pressure than those who did not adhere and their diastolic blood pressure also
decreased from 2.7 to 3 mmHg (Morris et al., 2006). Adherence of greater and equal
to 80% to antihypertensive drugs decreased the risk of cardiovascular disease by 22%
compared with the lower adherence group (< 80%) (Kettani et al., 2009). In addition,
the study of Perreault et al. (2009) found that a high adherence level (95%) to
antihypertensive therapy was associated with an additional reduction of chronic heart
4
failure. Lower left ventricular mass occurred in the group of hypertensive patients
who adopt a DASH diet and weight management by regular exercise 3 times per week
decreased the risk of cardiovascular disease when compared with those who adopt a
DASH alone (Blumenthal et al., 2010).
The impact of poor adherence to therapeutic regimens are increased of
health care costs and increased length of hospitalization. A study of the impact of
poor adherence to antihypertensive agents on clinical outcomes and hospitalization
costs found that hospitalized patients who had a low adherence to antihypertensive
therapy increased costs by approximately $3,574 per person within a 3 year period
(Dragomir et al., 2010). The average costs in the low adherence group were $1,370
for medical costs, and $3,995 for hospitalization, but the costs decreased to $1,346,
and $2,464, respectively, for the high adherence group. The average length of
hospitalization in the low adherence group was 16 days compared with 10.6 days for
the group with the high adherence. A low level of adherence increased the risk of
hospitalization compared with the high adherence group (Dragomir et al., 2010).
Because of the benefit of adherence to therapeutic regimens (medication and lifestyle
modifications) to decrease blood pressure level, complications and the cost of
treatments, improving adherence to therapeutic regimens needs to be promoted among
persons with hypertension.
Although adherence to therapeutic regimens has shown benefits for
hypertensive patients, the rate of adherence among hypertensive patients was still rate.
In developed countries, only 50% of patients with chronic illness adhered to regimen,
and the adherence rate was higher than developing countries (WHO, 2003). For
example, 43% of Chinese and 51% of Americans having hypertension had high
5
medication adherence (WHO, 2003). Kim et al. (2007) reported that approximately
45% of the Korean Americans with high blood pressure were adherent to regimens.
In Thailand, there was no national report to represent the rate of adherence among
persons with hypertension. They were represented in the research. For instance,
Naewbood (2005) who studied factors related to medication adherence among persons
with hypertension reported that 12.8% of persons with hypertension had poor
medication adherence. Moreover, Limcharoen (2006) found that persons with
hypertension had a lower level than cutting point (80%) of adherence to exercise
behaviors (77.9 %) and eating behaviors (77.35).
From the literature review it was found that several factors are associated
with adherence to therapeutic regimens including medication taking and lifestyle
modifications. Factors associated with adherence to therapeutic regimens include age
(Hadi & Rostami-Gooran, 2004; Hassan et al., 2006; Limcharoen, 2006; Naewbood,
2005), gender (Limcharoen, 2006; Naewbood, 2005; Phosena, 2003), income
(Charoenkij, 2000; Naewbood, 2005; Uzun et al., 2009), educational level
(Naewbood, 2005; Saounatsou et al., 2001; Uzun et al., 2009), marital status (Morris
et al., 2006; Tantayothin, 2003), knowledge of hypertension (Kim et al., 2007;
Limcharoen, 2006; Nangyeam, 2007; Uzun et al., 2009), health belief (DiMatteo,
Haskard, & Williams, 2007; Metha, 2001; Nangyeam, 2007), perceived self-efficacy
(Charoenkij, 2000; Charoenkitkarn, 2000; Dongyan, 2000; Roh, 2005), follow-up
interval (Bardel, Wallander, & Svardsudd, 2007; Hadi & Rostami-Gooran, 2004),
number of illness (Hadi & Rostami-Gooran, 2004; Phosena, 2003; Uzun et al., 2009),
duration of therapy (Hadi & Rostami-Gooran, 2004; Nangyeam, 2007; Onchim,
2002), number of pills per day (Fung, Huang, Brand, Newhouse, & Hsu, 2007;
6
Limcharoen, 2006), number of side effects (Kim et al., 2007; Naewbood, 2005),
social support (DiMatteo, 2004; Naewbood, 2005; Uzun et al., 2009) and provider-
patient communication (Roh, 2005; Schoenthaler et al., 2009; Xu, 2005). In brief, the
factors affecting adherence to therapeutic regimens are intrapersonal factors,
interpersonal factors, condition-related factors, therapy-related factors and health care
system-related factors. Some factors cannot be modified such as demographic
factors, condition-related factors and some factors can not be modified by nursing
roles alone such as therapy-related factors.
Adherence to therapeutic regimens is complex and simultaneously affected
by many factors. Previous models of adherence have been developed to explain this
phenomenon including the Five Dimensions Model of Adherence (WHO, 2003),
Medication Adherence Model (MAM) (Johnson, 2002) and Hill-Levine model
(Fongwa, Evangelista, & Doering, 2006). The Five Dimensions Model of Adherence
focuses on social/economic factors, patient-related factors, condition-related factors,
therapy-related factors and the health system and health care team-related factors
affecting adherence behaviors. The Five Dimension Model of Adherence has
advantages for assessing affecting factors in all aspects. Secondly, Medication
Adherence Model (MAM) was developed by Johnson to explain the process of
medication adherence (Hsu, Mao & Wey, 2010; Johnson, 2002). This model focuses
on the cognitive and behavioral processes which persons with hypertension use to
decide, establish and maintain their medication behaviors to control blood pressure. It
is advantagous to understand how patients create and maintain their adherence
behaviors and it is concerned with the two types of nonadherence behaviors
(intentional and unintentional nonadherence). Lastly, the Hill-Levine model focuses
7
on intrapersonal (cognitive and behavior), social factors and access to health care
services. Although it is an advantage to understand adherence phenomenon, some
factors such as access to health care services (presence or absence of health insurance,
regular treating physician and use of emergency department of hypertension-related
care), living arrangement and social isolation are unable to be modified by nursing
roles. Both the Five Dimensions Model of Adherence and the Hill-Levine model
focus on intrapersonal, interpersonal and environmental factors which affect
adherence, whereas the Medication Adherence Model focuses on the cognitive and
behavioral processes of individuals to decide and maintain medication behavior.
Although, the three models of adherence have advantages to explain factors affecting
adherence, they also have limitations. The limitations of the Medication Adherence
Model are focusing only on medication adherence and unable to demonstrate
adherence to lifestyle modifications. The limitations of both the Five Dimensions
Model of Adherence and the Hill-Levine model are that some factors in these models
cannot be modified and some factors cannot be modified by nursing roles.
Because of the importance of adherence in managing hypertension, a full
understanding of adherence to therapeutic regimens and its affected factors in Thai
persons with hypertension is needed in order to develop nursing intervention to
enhance adherence to therapeutic regimens. Nurses have important roles in teaching
and coaching hypertensive patients to adhere to regimens (Ockene, Hayman,
Pasternak, Schron, & Dunbar-Jacob, 2002). Nurses can also encourage hypertensive
patients to maintain healthier lifestyles by providing knowledge and support and
increasing patients’ confidence to perform recommended behaviors. Although, many
studies showed the relationship between sociodemographic factors, such as age,
8
marital status and socioeconomic status and adherence to regimen, the American
Heart Association has summarized that sociodemographic factors, socioeconomic
status and personality characteristics have weak and inconsistent effects on adherence
(Borzecki, Oliveria, & Berlowitz, 2005). Some related factors are non-modifiable.
Some modifiable factors are unable to be changed by nursing roles. Moreover,
several studies indicated that some factors such as social support (Khuwatsamrit,
2006; William & Bond, 2002), provider-patient communication (Roh, 2005; Xu,
2005), and knowledge of hypertension (Xu, 2005) had both direct and indirect effects
on adherence to therapeutic regimens among persons with hypertension.
Although, many studies show influencing factors on adherence to
therapeutic regimens, most of these studies focused only on medication adherence
among hypertensive patients (Hadi & Rostami-Gooran, 2004; Karaeren et al., 2009;
Kim et al., 2007; Naewbood, 2005; Phosena, 2003; Ross, Walker, & MacLeod, 2004;
Saounatsou et al., 2001). There are few studies which demonstrated the relationship
between related factors and each of lifestyle modifications such as nutritional
behavior (Charoenkij, 2000; Metha, 2001; Nangyeam, 2007), exercise behavior
(Charoenkitkarn, 2000; Tantayothin, 2003; Trivedi, Ayotte, Edelman, & Bosworth,
2008) and stress management (Riounin, 2007) but there is no study which indicated
the relationship between related factors and all lifestyle modifications. Few studies
focus on adherence to both medication and lifestyle modifications among
hypertensive patients (Limcharoen, 2006; Roh, 2005; Uzun et al., 2009). To date, the
factors that affected adherence to therapeutic regimens including medication and
lifestyle modifications among Thai persons with hypertension were not clearly known
and there is still a gap in the knowledge. In Thailand, there are two studies of
9
adherence to therapeutic regimens among persons with hypertension. One study
investigated factors related to medication adherence among persons with hypertension
(Naewbood, 2005). It focused only on medication adherence and the findings showed
that knowledge of hypertension and medication use, and educational level could
predict medication adherence at 19.7% (Naewbood, 2005). Another one has assessed
factors related to adherence to treatment both medication and lifestyle modifications
among essential hypertensive patients (Limcharoen, 2006). The results indicated that
there was a positive significant relationship between knowledge of hypertension and
medication adherence and adherence to lifestyle modifications (Limcharoen, 2006).
Moreover, a survey of existing non-experimental nursing research among patients
with hypertension in Thailand conducted during 1978-2005 found that only a few
researches have determined factors affecting treatment compliance (Khamhown,
2007). Also the previous models have the limitations that some factors are unable to
be modified by nursing roles.
Thus, the model of adherence to therapeutic regimens, including
medication and lifestyle modifications among Thai persons with hypertension, need to
be developed to fill a gap in the knowledge. The present study will develop a new
model of adherence based on empirical evidences which indicate direct and indirect
effects of factors on adherence to therapeutic regimens among persons with
hypertension. Therefore, to select factors affecting adherence to therapeutic regimens
to explain the model of adherence is based on empirical evidences which obviously
indicate direct and indirect effects of the selected factors on adherence to therapeutic
regimens and the selected factors can be managed by nursing roles. The studies of
modifiable factors influencing adherence to therapeutic regimens in persons with
10
hypertension and other chronic illness show that the significant modifiable factors are
social support, provider-patient communication, knowledge of hypertension, health
belief and perceived self-efficacy.
Social support is perceived and provided support from other people
including emotional, instrumental, informational and appraisal support. Social support
was associated with adherence; patients who perceived high social support were more
adherent than those who perceived low social support (Naewbood, 2005). DiMatteo
(2004) found that social support had a correlation with patients’ adherence to medical
treatment in various chronic diseases including hypertension. Patients who received
support had a higher adherence than those who did not. Several empirical studies on
social support found that social support and adherence were mediated by perceived
self-efficacy (Khuwatsamrit, 2006; William & Bond, 2002). Also, social support was
significantly directly related to knowledge among hypertensive patients (Roh, 2005).
Thus, social support may have a direct effect on adherence to therapeutic regimens,
knowledge of hypertension and perceived self-efficacy. Also, social support may
indirectly affect adherence to therapeutic regimens through knowledge of
hypertension and perceived self-efficacy.
Provider-patient communication is one aspect of a relationship which
induces trust, satisfaction, and confidence for patients to perform the required
behaviors (Vermerire, Hearnshaw, Royen, & Denekens, 2001). Exchanging
information between patients and health care providers is one purpose of
communication and improves patients’ knowledge and perceived self-efficacy to
perform the required behaviors. Patients, who perceived collaborative communication
from their providers, had higher adherence than those who perceived non-
11
collaborative communication with providers (Schoenthaler et al., 2009). Also,
provider-patient communication had a direct positive effect on perceived self-efficacy
and an indirect positive effect on adherence to therapeutic regimens among
hypertensive patients (Roh, 2005). In the diabetes study of Xu (2005) it was found
that provider-patient communication had a positive direct effect on perceived self-
efficacy and knowledge and had a positive indirect effect on self-management in type
2 diabetes. Thus, provider-patient communication may have a direct positive effect
on adherence to therapeutic regimens, perceived self-efficacy and knowledge of
hypertension among hypertensive patients and have an indirect positive effect on
adherence to therapeutic regimens through perceived self-efficacy and knowledge of
hypertension.
Knowledge of hypertension is the cognitive process which establishes
patients’ understandings of their illness and treatment plan for controlling their illness.
In addition, it also affects the patients’ decision to adhere to therapeutic regimens.
Knowledge is associated with adherence to therapeutic regimens when knowledge of
hypertension increases, adherence to therapeutic regimens also increases (Limcharoen,
2006; Naewbood, 2005; Nangyaem, 2007; Uzun et al., 2009). Moreover, Xu (2005)
who studied Chinese with type 2 diabetes found that knowledge was positively
associated with perceived self-efficacy and had a positive indirect effect on self-
management. Hence, knowledge of hypertension may have a direct effect on
adherence to therapeutic regimens and an indirect positive effect on adherence
through perceived self-efficacy.
Health belief is a modifiable factor which influences adherence to
therapeutic regimens. Health belief refers to individual’s subjective probability
12
decision concerning hypertension and its treatment. Patients who perceived the risk
of complications, perceived the severity of those complications, perceived the
usefulness of performing adherence and perceived fewer barriers to performing
adherence were more adherent to therapeutic regimens (Metha, 2001; Nangyaem,
2007; Riounin, 2007; Tantayothin, 2003). In conclusion, health belief may positively
affect adherence to therapeutic regimens among hypertensive patients.
Lastly, perceived self-efficacy is the patients’ perception of their own
ability to perform adherence behaviors. Most studies indicated that perceived self-
efficacy was a powerful factor influencing adherence to therapeutic regimens among
hypertensive patients (Dongyan, 2000; Kressin et al., 2007; Onchim, 2002;
Tantayothin, 2003). Patients, who had high perceived self-efficacy, are likely to
perform the required behaviors. Additionally, perceived self-efficacy is the mediating
factor between adherence to therapeutic regimens and social support and provider-
patient communication. Many studies indicated perceived self-efficacy as a
mediating factor. Perceived self-efficacy was a mediator between provider-patient
communication and adherence to therapeutic regimens among hypertensive patients
(Roh, 2005). Also, the finding in type 2 diabetes found that perceived self-efficacy
was a mediator between self-management and social support, provider-patient
communication and knowledge (Xu, 2005). The result in the study of patients with
coronary artery disease showed that perceived self-efficacy was a mediator between
adherence to self-care requirements and knowledge and social support (Khuwatsamrit,
2006). In summary, perceived self-efficacy may have a positive direct effect on
adherence to therapeutic regimens among hypertensive patients and may serve as a
13
mediator between adherence to therapeutic regimens and knowledge of hypertension,
social support and provider-patient communication.
The role of the modifiable factors influencing adherence to therapeutic
regimens among Thai persons with hypertension is not clearly known and less
studied. Therefore, this study will fill this gap in the knowledge by developing the
model of adherence to therapeutic regimens in order to enhance the understanding of
the direct and indirect effects of modifiable factors on adherence to therapeutic
regimens among Thai persons with hypertension. Once this information is obtained,
the model of adherence will be essential to nursing knowledge for assessing the
factors affecting adherence to therapeutic regimens and developing effective nursing
intervention to improve and promote adherence to therapeutic regimens in Thai
persons with hypertension.
Research Objectives
The general objective of this study is to test a model of adherence to
therapeutic regimens among persons with hypertension.
The specific objectives of this study are:
1. To examine the relationships between social support, provider-patient
communication, knowledge of hypertension, health belief, perceived self-efficacy and
adherence to therapeutic regimens among persons with hypertension.
2. To identify factors directly and indirectly affecting adherence to
therapeutic regimens among persons with hypertension.
14
Research Questions
The research questions for this study are as follows:
1. What relationships are there between social support, patient-provider
communication, knowledge of hypertension, health belief, perceived self-efficacy
and adherence to therapeutic regimens among persons with hypertension?
2. What factors have direct and indirect effects on adherence to
therapeutic regimens among persons with hypertension?
Scope of the Study
This was adescriptive, cross-sectional, predictive correlation design was
used to identify predictors and test a causal model of adherence to therapeutic
regimens in persons with hypertension who attened hypertension clinic in one of the
community hospitals in Lampang province, Thailand. Data were collected from May
to July 2012.
Definition of Terms
Adherence to therapeutic regimens. It is defined as the extent of
agreement and performance of persons with hypertension about the recommended
behaviors provided by health care providers including antihypertensive medication
taking, dietary modifications, weight control, avoiding risk factors, physical activity,
stress management and follow-up visits. The attributes of agreement consist of
alignment of patients’ behaviors and recommendations, mastery of new behaviors,
15
ongoing collaboration with health care providers on the treatment plan and their
perceived ability to meet optimal blood pressure. It was measured by the
Hypertensive Adherence to Therapeutic Regimens Scale which was modified from
the Hypertensive Adherence Scale (Limcharoen, 2006).
Provider-patient communication. It is defined as the level of patients’
perception of health care provider’s behaviors about general clarity during their
talking, explanation of hypertension medication and lifestyle modifications and
carefully listening to and responding to patient problems and concerns about
hypertension management. The Provider-patient Communication Scale modified by
Xu (2005) was modified to measure the provider-patient communication in this study.
Knowledge of hypertension. It is defined as the level of understanding
regarding hypertension, including etiology, signs and symptoms, complications,
medication and behavioral modification to control blood pressure (dietary, physical
exercise, weight control, avoiding risk factors, stress management and follow-up
visit). The Knowledge of Hypertension Scale modified from the Hypertension
Knowledge Scale developed by Limcharoen (2006) was used to measure the
knowledge of hypertension in this study.
Social support. It is defined as the level of emotional, instrumental,
information and appraisal support perceived by hypertensive patients in order to
maintain an adherence to therapeutic regimens. The Hypertensive Social Support
Scale developed by Pongudom (2006) was modified to measure social support in this
study.
Health belief. It is defined as the level of the perception of hypertensive
patients including perceived susceptibility to the hypertensive complications,
16
perceived severity of the hypertensive complications, perceived benefits of
performing disease control behaviors and perceived barriers to performing disease
control behaviors. The Health Belief for Hypertensive Patient Scale developed by
Riounin (2007) was modified to measure health belief in this study.
Perceived self-efficacy. It is defined as the level of the confidence a person
with hypertension has that he/she can be successful in the activities recommended by
the health care providers. These activities include taking of antihypertensive
medication, dietary modifications, weight control, physical exercise, avoiding risk
factors, stress management and follow-up visits in order to control their own blood
pressure. The Hypertensive Self-efficacy Scale developed by Kairoj (1999) following
of Bandura’s self-efficacy theory, was modified to measure perceived self-efficacy.
Persons with hypertension. They are defined as persons who have been
diagnosed with essential hypertension and take at least one antihypertensive
medication.
Recommended