Essay title - A review of the literature relating to the relationship between Diabetes and Coronary Heart Disease and the role of the nurse in client care and management.
Introduction and Methodology
The literature on the association between diabetes and coronary heart disease suggests that there are certain commonalities found which can be attributed to the two conditions, and certain significant findings which make this an important topic for review and consideration in relation to healthcare practice in general and nursing practice in particular. The most significant point is that coronary heart disease remains the biggest cause of adult mortality in the United Kingdom (Camm, 1998, cited in Kumar and Clarke, 1998). Although the numbers of patients with coronary heart disease are decreasing slightly across the Western world, which is chiefly due to the improved rates of detection of risk factors and initiation of preventive strategies (Camm, 1998, cited in Kumar and Clarke, 1998), the disease still poses one of the most significant risks for morbidity and mortality in the UK. The predominant risk factors for coronary heart disease include smoking, obesity, and sedentary lifestyles (Mann, 2002), along with hypertension (high blood pressure), higher blood cholesterol levels (Tortora & Grabowski, 1996), being of male gender (Wild & Byrne, 2006), and, significantly, any diabetic disease (Grundy et al, 1998). Coronary heart disease is known to be a disease of the Western world, with rates significantly lower in the developing world, perhaps due to differences in lifestyles. The same is true of rates of diabetes, although there are certain ethnic groups with a higher predisposition towards developing diabetic disease, such as Afro-Caribbeans, Hispanic people, and those of Asian race (Grundy et al, 1999).
There is a worrying trend within the UK of rates of diabetes increasing, perhaps related to the way the population is gradually ageing, and also due to increased rates of sedentary or non-active lifestyles and higher rates and severity of obesity (Wild & Byrne, 2006). These are also risk factors for coronary heart disease. While there are a range of disorders associated with diabetes-type illness, Diabetes is classified into two types, non-insulin-dependent [NIDDM] (type 2) and insulin-dependent [IDDM] (type 1). The most common form of diabetes is NIDDM (type 2), with over 90% of those classified as diabetic presenting with this type of disease, which used to be called maturity-onset diabetes, relating the disease to the fact that it tends to appear later on in life. This type of diabetes is related to metabolic abnormalities, with a combination of impairment in insulin mediated glucose metabolism, described as insulin resistance, and insufficient secretion of the hormone insulin from the beta cells in the islets of langerhans in the pancreas. This combination leads to hyperglycaemia and a range of associated health consequences. The principle causes of Type 2 Diabetes appear to be obesity and physical inactivity, both of which can cause insulin resistance, and age, because insulin secretion declines with advancing chronological age, which may be exacerbated genetic causes (Grundy et al, 1999).
Type 1 Diabetes is usually diagnosed early on in life and is often referred to as juvenile-onset diabetes. This disorder classification relates to patients who cannot live without insulin replacement therapy (Williams & Pickup, 1998). According to Wiliams and Pickup (1998), the UK rate of Type 1 Diabetes is 0.25 per cent.
It has already been indicated that the weight of epidemiological and pathological evidence presents a strong indication that diabetes is an independent risk factor for coronary heart disease, in women and in men, but that while women have a lower risk for developing the disease than men, women with diabetes tend to lose most of their apparent inherent protection against developing coronary disease(Whitely et al, 2005). There is clear evidence in the significant array of clinical and scientific evidence within the literature that that diabetes is an independent risk factor for all forms of cardiovascular disease, including coronary heart disease, heart failure, stroke and peripheral arterial disease (Soedamah-Muthu et al, 2006). Of more concern is the fact that this same evidence demonstrates that despite recent advances in knowledge, treatment and care, the risk of patients with diabetes developing coronary heart has not decreased and, instead, appears to continue to rise, and there is still a failure to achieve recommended treatment targets and management outcomes of patients with type 2 diabetes (Yong, 2007).
There appear to be two main approaches to a diagnosis of CHD and diabetes, are prevention and treatment. Nurses involved in these conditions appear to be primarily involved in prevention and risk reduction. Prevention of the development of coronary heart diseasein an individual with diabetes, would mainly take the form risk reduction through of health promotion and education, focusing on lifestyle changes, dietary modification, exercise and regular activity, and other individualised interventions. This dissertation will address the role of the nurse in the care of diabetic patients and the prevention of cardiovascular disease risk in this client group, looking at a a new, adapted model of health promotion and nurse intervention, posited as a possible solution to the significantly increased risks of coronary heart disease, and increased severity of this condition, including increased risk of mortality.
The aim of the literature review was to identify and explore the relationship between diabetes and coronary heart disease, and from this review identify risk factors, the role of the nurse and recommendations for future best practice. In order to achieve a comprehensive literature review, it was necessary to take a systematic approach to reviewing the literature, using a sequence of methodological steps to address the available published literature. The author aimed to review in detail five primary research studies which address the research question, alongside a general review of the other available literature.
The process began with identification of search terms, as listed below:
- Diabetes + cardiovascular disease
- Diabetes + coronary heart disease
- Diabetes + risk factors
- Coronary Heart Disease + risk factors
- Diabetes + coronary heart disease + role of the nurse
- Diabetes + coronary heart disease + best practice
The search terms were used in combined searches in the following gateways:
- Cinahl
- Embase
- British Nursing Index
- Ovid
Search limits included: articles published in the last ten years; primary research articles; articles in English. The search was subsequently extended to explore articles older than ten years for background reading only, and to allow the researcher to evaluate the evolution of theory within this field. The search was not limited to UK articles as the field of investigation is of international significance, and there are a number of large, international studies which inform the review.
The search terms were also used to search the Internet using Google, with the addition of the term ‘guidelines’, to identify any national guidelines which would inform nursing practice and future best practice in the prevention of the two conditions. Although there are significant limitations of using such a search engine, Google does allow for the limitation of a search to UK-associated websites, and proved useful in identifying British and European guidelines to inform this review.
Of the articles returned, the abstracts were read to evaluate their relevance and usefulness to the literature review, and then for those deemed relevant to the study, the full text of the article was reviewed and a decision was made whether or not to include the studies within the literature review. The complexity of the research question was discovered during the searching process, as the varying disorders associated with the term diabetes (such as Type 1 diabetes, Type 2 diabetes, pre-diabetes, and insulin resistance) and the varying disorders associated with cardiovascular disease (atherosclerosis, coronary heart disease, coronary heart failure, stroke, hypertension) meant that a vast array of literature was returned. Focusing the literature review on the relationship between the two conditions was not easy, and identifying appropriate articles for review was very time consuming. Those articles which were not immediately available in full were ordered from the British Library, which also took time. However, there were sufficient primary studies identified for detailed critical analysis, and a number of further articles which augmented the discussion. The following discussion is segmented under subheadings which directly address key elements of the research question.
Discussion
The Association between Diabetes and Coronary Heart Disease
The impact of diabetes on individuals, on families and society in general is significant (DH, 2002), and can be seen as a national problem as it affects as many as 1.4 million people within the UK (Hilton and Digner, 2006). In 2002, the Department of Health published the National Service Framework (NSF) for Diabetes in 2002, setting standards for the diagnosis and management of diabetes, in order to manage its impact on NHS services and address the potential for prevention and reduction of risk(DH, 2002).
As stated a above, Diabetes is separated into two chief types, defined by elevated blood glucose levels which are due to either a lack of insulin or an insufficient response to insulin within the body (DH, 2002). Insulin regulates blood glucose levels, and normo-glycaemia is a homeostatic state which is in constant balance. In Type 1 Diabetes, it is theories that the body’s immune system responses have destroyed the insulin-producing cells, Beta cells in the Islets of Langherhans (DH, 2002; Watkins, 2003). This is the most severe form of the disease, with sufferers requiring either lifelong insulin therapy or pancreatic transplant (which is rare). In Type 2 diabetes, also known as maturity-onset diabetes because it tends to occur later in life there is both a decreased output of reduction and an impaired response to insulin within the body, known as insulin resistance (Watkins, 2003).
Coronary heart disease is characterised by impaired cardiovascular function, leading to hypo-oxygenation of the cardiac muscle secondary to atherosclerosis (typically). This can be due to reduced oxygenated blood flow, due to narrowing of the arterial space, vascular rigidity and an increased risk of thrombotic disease with consequent risk of myocardial infarction, cerebrovascular accident and pulmonary embolism (Guthrie and Guthrie, 2004). Diabetes causes macrovascular complications which have a number of side effects, including the significant increase in atherosclerosis which contributes to the risk of developing this serious disorders (Guthrie and Guthrie, 2004;n Bloomgarden, 2005; Soedmah-Muthu, 2006; Fowler, 2008).
Diabetes and poor glycaemic control have other consequences, including diabetic retinopathy (Guthrie and Guthrie, 2004) neuropathy and gastrointestinal disturbance, peripheral vascular disease and foot and leg ulceration; erectile dysfunction in males; glomerular damage and kidney failure (Guthrie and Guthrie, 2004).
There is no doubt from the literature that there are links between the two disorders, diabetes and coronary heart disease. Kannel and McGee (1979) reported the Framingham study, a 20 year study of a cohort of study participants which related subsequent cardiovascular events to prior evidence of diabetes. This seminal study found a twofold to threefold increased risk of clinical atherosclerotic risk of cardiovascular disease in cases of diabetes (Kannel and McGee, 1979). The study did find that coronary heart disease was the least significant risk, but that the impact was greater for women than for men, and for each of the diseases reported on, morbidity and mortality were higher for diabetic women than for nondiabetic men (Kannel and McGee, 1979). What this study demonstrates is clear evidence of a link between cardiovascular disease risk and diabetes, and an associated increase in morbidity and mortality for both women and men (Kannel and McGee, 1979). Barengo et al (2008) support these findings, and show that the presence of diabetes also increases the case fatality in patients who suffer acute coronary events. Otter et al (2007) link atherosclerosis with chronic low-grade inflammation of the vasculature and vascular endothelial cells, and diabetes is a risk factor for this.
Just what these links are, however, warrants further investigation. Bianchi et al (2008) report that cardiovascular disease accounts for the largest proportion of deaths in patients with type 2 diabetes, with an increased rate of fatality after myocardial infarction in this client group. Bianchi et al (2008) refer to experimental studies which show that increased glucose level appears to trigger multiple mechanisms of susceptibility to atherosclerosis. Stakos et al (2007) suggest a link between the marker of higher glycosylated haemoglobin concentration and cardiovascular disease, specifically stiffer aorta and increased left ventricular mass, which can be present in diabetic individuals and non-diabetic individuals with insulin resistance. Herrero et al (2008) attempt to look at the underlying causal link between the two conditions, and so investigated if myocardial fatty acid utilization and myocardial fatty acid oxidation are increased in patients with diabetes. There are complex physiological mechanisms involved, but essentially, if these processes are increased, this can lead to a greater susceptibility for cardiac ischaemia and a decreased capacity of the myocardium to oxidise fatty acids, reducing cardiac efficiency. This rigorous study, with a sample controlled to rule out a range of confounding variables, including effects of exercise on myocardial function, smoking, hypertension, and other diseases (for example) Herrero et al (2008). Results are presented graphically, in tabular form and discussed in textual form, and clearly show a link between Type 1 diabetes and persistently elevated free fatty acid levels which have detrimental effects on the myocardium (Herrero et al, 2008). The authors suggest that this provides “a partial explanation for the more pronounced manifestations of coronary artery disease, such as increased infarct size, heart failure, and sudden death that occur with ischemic events in diabetic patients” (Herrero et al, 2008 p 603). Managing fatty acid levels might be a future target for therapy and prevention (Herrero et al, 2008). This study has a number of limitations, including some of the exclusion criteria, the failure to include type 2 diabetes in the study, and the fact that some variables were not included, such as left ventricular function, suggesting that there is the capacity for further research to clarify this biological picture. The study also requires considerable physiological knowledge and acumen for true understanding, and so may be inaccessible to some practitioners. However, the fact that it demonstrates a link between physiological mechanisms associated with diabetes and the mechanisms of coronary heart disease means it is a significant contribution to the knowledge base about this association.
Whitely et al (2005) directly address the link between diabetes and coronary heart disease, referring to a 25 year follow up on the Renfrew and Paisley survey. The discuss the original study which had a cohort of 7,052 men and 8, 354 women subjects, looking at all-cause mortality in terms of death per 1,000 person-years. While the study language is somewhat dense and challenging for the reader, the report outlines clearly the purpose of the study:
“to examine long-term CHD and other vascular mortality associated with having diabetes only, CHD only, both, or neither in a population survey of >15,000 middle aged men and women who were followed for 24 years. Specifically, we wished to confirm or refute the view that diabetes be considered a CHD risk equivalent and to test for possible sex differences in outcome” (Whitely et al, 2005; p 1588).
This study has a great impact on the knowledge about the link between diabetes and risk of CHD. The sample size and timespan are large enough for the results to be statistically significant, the methods are clearly stated and inclusion/exclusion criteria listed and entirely suited to the study focus. Data are presented in textual, tabular and graphical form, and strengths and weaknesses of the study are cited. Self-reporting is a weakness, but adjustment for the effects of significant confounding variables is a strength (Whiteley et al, 2005). It appears that the study has methodological strength and clearly outlines a link between diabetes and in creased risk of cardiovascular disease (Whitely et al, 2005).
Daousi et al (2006) carried out a study to “determine the prevalence of overweight and obesity among patients with type 1 and type 2 diabetes mellitus…and to assess the impact of overweight and obesity on glycaemic control and cardiovascular risk factors in patients with type 2 diabetes” (p 280). While this study is limited by its attempt to address a wide range of outcomes, it does address a large enough sample and utilise appropriate study instruments, including appropriate statistical methods, such as the t-test for looking at the differences between obese and non-obese patients, and the use of appropriate biological markers such as HBA1c (Daousi et al, 2006). Daousi et al (2006) clearly confirm the link between obesity/overweight and type 2 diabetes, unlike type 1 diabetes, but their most significant finding is a correlation between obesity and the increased risk of cardiovascular disease. According to Daousi et al (2006) “obesity in type 2 diabetes was associated with poorer glycaemic contol, blood pressure, and lipid profiles, and increased use of lipid lowering and antihypertensive drugs” (p 283). Although they admit insufficient methodological strength to establish causality from their study. The difficulties in using data gathered for clinical purposes are included as a limitation of this study, but overall it shows a link between obesity as a risk factor for both diabetes and cardiovascular disease (Daousi et al, 2006).
Bowden et al (2006) report on the Diabetes Heart Study and explore the linkage between type 2 diabetes, metabolic syndrome, and measures of cardiovascular disease.
“The Diabetes Heart Study is being conducted … to study the genetic and epidemiological origins of CVD in families affected with type 2 diabetes.” (Bowden et al, 2006 p 1986).
The authors clearly define the inclusion criteria, the study sample and its characteristics, exclusion criteria (eg patients with serious health conditions were excluded), and some aspects of recruitment are discussed (Bowden et al, 2006). However, given the nature of the study, which is recruiting siblings from certain families, there is little attention paid to ethical issues in relation to recruitment and inclusion in the study, and this could be a methodological weakness. Again, this study is based on clinical findings, including ECGs, clinical blood tests, blood pressure and the like, and the presence of calcified atherosclerotic plaque, coronary calcified plaque, and carotid calcified plaque, alongside the genome scan (Bowden et al, 2006). The authors provide sufficient detail about the tests and measures used, and they do seem appropriate, and consistent with other studies (eg…). The authors also clearly define their parameters of cardiac disease, metabolic disease and diabetes, which is a strength in this study. Results are presented in graphic and tabular form, and linkage analyses are carried out using appropriate statistical approaches. However, the advanced nature of these analyses are such that the process is very dense and may be inaccessible to the non-specialist reader or the professional who does not have a very high level of understanding of statistics.
Bowden et al (2006) found that there was a link between what they describe as the qualitative traits of type 2 diabetes and a “coincident linkage” in certain chromosomal regions. This suggests some sort of genetic foundation to the disease, but the authors admit that there are limits to their findings, and that these should indicate that “identification of the underlying genes may help clarify the relationship of CVD, diabetes and metabolic syndrome” (Bowden et al, 2006 p 1992). This study shows a potential genetic predisposition towards diabetes and some of its associated conditions, but the authors admit to some limitations of the study, including their areareness “that the definition of prevalent CVD in this study may not be robust, as we relied upon self-report of events and procedures” (Bowden et al, 2006 p 1993). While some would argue that this demonstrates the paternalism of quantitative research in consistently undermining the validity of studies that are self-reported, placing the patients themselves as unreliable witnesses, as it were, within the quantitative paradigm, this does represent a weakness of the study.
The authors have concluded that this argues for further identification of the genes which connect diabetes and cardiovascular disease (Bowden et al, 2006). This adds to the understanding of the connection between the two disorders, and may also represent another valuable contribution to clinical practice, because it may help those with type 2 diabetes, in particular, to come to terms with their disease, whilst also providing ammunition to challenge dominant negative stereotypes of patients with this disease. Perhaps because of the linkage between type 2 diabetes and obesity, and particularly in the UK, there appears to be a subtle ‘blame’ culture in which such individuals are thought to be responsible for the development of the disorder. Identifying an underlying genetic causative factor might help to change the negative attitudes of some, lay people and professionals alike. Barengo et al (2008) show that developmental cycle models of diabetes link obesity, urbanized and sedentary lifestyles, and a better understanding of these factors might help with prevention programmes.
Avogaro et al (2007) carried out a four year follow up of a cohort of patients from hospital-based diabetes clinics, to “determine incidence and identify predictors (including macrovascular complications and treatment) of first coronary heart disease (CHD) even in CVD-free type 2 diabetic patients” (p 1241). The authors do not provide a detailed methodology, stating that it has been reported in other studies (Avogaro et al, 2007). While this is a standard convention in scientific literature, this author believes this is a failing as it does not allow the article to stand alone and to be evaluated without referring to the other studies. Therefore, the author cannot, for example, evaluate methodological quality or the ethical dimensions to the study, although there is sufficient information about the sample to suggest a robust sampling technique. There is clear discussion of data collection processes, although the questionnaire itself is not included and so the reader cannot evaluate this data collection tool. Clinical and other measurements are listed, and statistical analyses are robust and suitable for the study size and type. One strength here is the terminology used to explain the statistical analysis, which is clear and more accessible to the nursing reader than some of the other studies were. Explaining, for example, “propensity score methodology” allowed a more ready understanding of this approach (Avogaro et al, 2007 p 1242). The results are presented in textual and tabular form, and this section of the article is very dense, exploring a large amount of data in detail. The authors conclude that “in CVD-free patients with type 2 diabetes, risk of first CHD event depends on sex, geographic location, and presence of microvascular disease”. (Avogaro et al, 2007 p 1241). This suggests that there are links between certain variables in diabetic patients and the development of coronary heart disease. The sex-related link is similar to other studies, but the variable of geographical location is an interesting one, although this is an Italian study and so the same kind of variation may not be transferable to other nations. The presence of microvascular disease as a risk factor is unsurprising given the biological consequences of these changes in diabetes.
Other studies demonstrate a link between diabetes and other forms of cardiovascular disease, including heart failure. Ahsrafian et al (2007) explore the metabolic mechanisms associated with heart failure, and discuss not only the epidemiological links between the two conditions, but also in particular the link between insulin resistance and heart failure. This may be related to myocardial metabolism, and adrenergic mechanisms that underline altered myocardial metabolism (Ahsrafian et al, 2007). This provides some indication of future treatment potential in prevention of heart failure: “novel insulin-sensitizing agents developed for the treatment of diabetes and effective in amelioration of metabolic profile may also prove effective in HF” (Ashrafian et al, 2007 p 443). Berry et al (2008) link abnormal glucose tolerance, diabetes and acute heart failure, and show that blood glucose levels can be an indicator of incipient heart failure and an indicator for more aggressive therapeutic interventions. Diabetic patients appear to have a poorer prognosis when they develop heart failure than non diabetic patients (Berry et al, 2008).
Diabetes is also linked to cardiomyopathy (Boudina and Abel, 2007). This is defined as “ventricular dysfunction that occurs independently of coronary artery disease and hypertension” and which can be associated with erectile dysfunction in men (Boudina and Abel, 2007 p 3213). This is a significant finding because the predominant focus is on the presence of cardiovascular disease as a real increase in risk of mortality and morbidity, and Boudina and Abel (2007) demonstrate that cardiomyopathy can increase morbidity and mortality in the absence of cardiovascular disease. This shows that diabetes itself may be an independent risk factor for cardiac dysfunction.
Risk Factors For Diabetes and Coronary Heart Disease
It is obvious from the literature that a large number of authors believe that diabetes should be considered a coronary heart disease risk equivalent (Bianchi et al, 2008). However, there is ongoing debate within the scientific literature about the correlations between the two diseases. Bowden et al (2006) discuss the different hypotheses which explore the individual risks for diabetes and for heart disease, and the relationships between them. Cardiovascular disease risks include insulin resistance, obesity, high HDL cholesterol, and hypertension, and these risk factors are thought to be increased in diabetes (Bowden et al, 2006). Barengo et al (2008) state that hypertension, hyercholesterolaemia, and smoking constitute the major risk factors for coronary heart disease and cardiovascular disease. The alternative view is that the increased risk of coronary heart disease is not caused by diabetes, but that “these two conditions share common antecedents” (Bowden et al, 2006 p 1986). Metabolic syndrome (characterised by insulin resistance) is suggested to be one of these common antecedents, while another is an inherent genetic susceptibility to both diseases (Bowden et al, 2006).
There is substantial evidence that there is a sex-related difference in risk for coronary heart disease, such that men are at increased risk than women (Huxley et al, 2006). However, it seems that the presence of diabetes appears to eliminate or reduce the advantage that women have over men in relation to coronary heart disease risk (Huxley et al, 2006).
Huxley et al (2006) carried out a meta-analysis of thirty-seven prospective cohort studies to explore this relationship: “to estimate the relative risk for fatal coronary heart disease associated with diabetes in men and women” (p 73). Meta-analyses feature on the spectrum of research evidence as a means by which the power of existing research studies can be evaluated. There is an underlying assumption that the more studies there are which posit similar findings adds power to the weight of evidence associated with those findings. Huxley et al (2006) provide a background to their study, set the scene and describe the studies included in their meta-analysis. They clearly outline their methodology of research retrieval and data extraction, which provides transparency, with clear inclusion/exclusion criteria which directly focus the review on the data pertinent to the research question. The size of the ‘sample’ of studies is large and sufficient for effective statistical analysis. The most significant finding was that the relative risk for fatal coronary heart disease associated with diabetes was much higher for women than it was for men (Huxley et al, 2006). The authors do discuss potential confounding variables or alternative explanations of this finding, however, such as, for example, a potential treatment bias that favours men with diabetes (Huxley et al, 2006). However, the increased risk may also be associated with “diabetes inducing a more adverse cardiovascular risk profile in women” (p 77). While there may be issues with any meta-analysis because of the way in which the included samples are determined, this study indicates that female gender is a significant risk factor for cardiovascular disease associated with diabetes.
Herrero et al (2008) demonstrate that the increased free fatty acid levels characteristic of type 1 diabetes contribute to the increased risk of CHD in diabetic patients, but make no gender differentiation, and do not include type 2 diabetics. Daousi et al (2006) show a link between obesity and overweight and diabetes, and the same link between obesity and cardiovascular disease, alongside a link between diabetes and cardiovascular disease. Further research is required however to properly explore what the correlations are between these three conditions. Boudina and Abel (2007) show that diabetes presents a significant increased risk of cardiomyopathy in the absence of other cardiovascular disease or hypertension, such that diabetes is an independent risk factor for some cardiac dysfunction.
The role of the nurse in the treatment and prevention of both Coronary Heart Disease and Diabetes
The available literature indicates that the kinds of interventions which contribute to the prevention of diabetes are also those which can contribute to the prevention of coronary heart disease. Bianchi et al (2008) argue that diabetes prevention trials demonstrate that activities to prevent conversion into diabetes are not only effective at achieving a reduction in rates of diabetes, but also bring about a significant improvement in cardiovascular risk factors. Therefore, it would appear that if nurses can engage in health promotion activities which prevent the development of incipient diabetes, then they are likely to reduce the rates of coronary heart disease.
Obesity is an established risk factor for cardiovascular disease and diabetes (Daousi et al, 2006). Reduction in body mass index is a significant health promotion concern in general, and in the prevention of cardiovascular and diabetic disease in particular. It would appear, from the studies included in this critical review of the literature, that a reduction in body mass index, and the implementation of programmes to manage obesity and prevent it occurring, through lifestyle changes, may be on of the most significant non-medical interventions available. Nurses involved in primary care in particular may have the potential to significantly reduce the risks of cardiovascular disease for diabetic and non-diabetic patients alike through the implementation of obesity prevention and reduction initiatives. As Barengo et al (2008) suggest, “more effort is needed to prevent the onset of diabetes and to decrease the incidence of diabetes and glucose metabolism disorders in the population” (p 1894). Better dietary habits and lifestyle changes which include a reorientation towards fresh fruit and vegetables would be an important area to help address obesity and the cardiovascular risk associated with diabetes. Nothlings et al (2008) report a study which found that “intake of vegetables, legumes, and fruit was associated with reduced risks of all-cause and CVD mortality in a diabetic population” (p 775). This shows that simple lifestyle changes can bring about significant changes in risk profiles for diabetic patients, which correlates with previously reported studies about the reduction of cardiovascular disease risk associated with fruit and vegetable intake (Nothlings et al, 2008). O’Neil and Nicklas (2007) also show that diet, physical activity, continues to be the area which needs most attention in terms of disease prevention and risk reduction. They demonstrate that lifestyle, diabetes and heart disease are clearly linked, and argue that “eating a diet high in fruits and vegetables with low-fat sources of dairy and protein” alongside sufficient levels of physical activity and exercise, are the key lifestyle factors affecting these conditions (O’Neil and Nicklas, 2007 p 457).
Nurses could, therefore, be involved in programmes which include nutrition assessment as the first step in promoting weight loss and management programmes, and in supporting patients to engage in behavioural treatments which would help individuals make small changes to support their weight loss activities (O’Neil and Nicklas, 2007). These changes should include building regular activity and exercise into their lifestyles, and could also include drug therapy, but this must be combined with lifestyle changes for proper effect (O’Neil and Nicklas, 2007). Nurses in all areas of the NHS, but particularly in primary care, can also contribute, through such changes, to a reduction in hypertension and other cardiovascular complications (O’Neil and Nicklas, 2007).
In terms of treatment, optimal management of established diabetes and good glycaemic control appears to be a nursing intervention with significant potential to reduce cardiovascular disease risk, because of the association between hyperglycaemia and coronary heart disease. “It is necessary to intensify the management and medical care of diabetes patients to decrease all events and mortality from CHD among them” (Barengo et al, 2008, p 1894).
Another potential area in which the nurse can make a significant contribution to prevention of the development of cardiovascular disease is in the promotion of preventive clinical or pharmacological treatment strategies for all diabetic patients. Huxley et al (2006) found that men with diabetes were more likely to be treated with aspirin, statins or antihypertensive medication than women with diabetes, which suggests not only a treatment bias but a significant potential to reduce the cardiovascular risk for all clients. Whiteley et al, (2005) recommend that all people with diabetes should be treated as if they already have vascular disease, and so are treated with cholesterol-lowering drug therapy sooner rather than later, to prevent further complications such as CVA and MI. Ashrafian et al (2007) show that the use of insulin-sensitising medications can be effective in prevention of diabetes-related heart failure. Giorda et al (2007) also show a role for nursing prevention strategies in reducing the risk of diabetic patients developing stroke, and show that the management of blood glucose, the proper use of medications and insulin, an the management of macrovascular complications and cholesterol can all contribute to a reduction in stroke risk. Air et al (2007) support the conclusion that glycaemic control is one of the key elements in stroke risk reduction.
Therefore, advocating for the early use of preventive treatments such as these might be an important nursing role, as would be the ongoing monitoring of medication use, multifactorial medication (Yokoyama et al, 2007), support with compliance, and ongoing monitoring (in conjunction with medical colleagues). Herrero et al (2006) clearly outline some of the metabolic and physiological mechanisms of diabetes which increase the risk for CHD, and if prevention programmes can focus on these mechanisms, there could be significant health benefits. It would be the responsibility of nurses within the primary and secondary healthcare fields to understand these mechanisms in order to develop and/or contribute to health promotion and disease management programmes that include these mechanisms. Nurses would also have to manage complex multiple morbidities in patients with diabetes, as prevention of cardiovascular risk might be complicated by a range of other co-existing conditions in diabetic patients (Balasubramanyam et al, 2006).
Nurses’ roles include meeting the acute and chronic needs of patients with diabetes, as well as engaging in healthcare which helps reduce the risks associated with their condition. This means they will engage with diabetic patients to manage emergencies, help them control and manage symptoms, prevent longer-term effects, reduce the risk factors in their lives such as obesity and smoking, and educate them in a way that will encourage independence and self-management (Watkins, 2003). The health promotion approach which might best be employed, based on clinical trials, would build on the evidence that modifications in lifestyle, combined with effective and appropriate health education, can be proven to aid in reducing risk for diabetic patients (Anthony et al, 2004). Traditionally, diabetes education programmes may have been very medically-focused, and Skinner et al (2003) suggest that the better results may be achieved on moving away approaches which are based on making patients compliant with healthcare professional-designed management, and towards initiatives which embrace on a client-centred approach. There is evidence within the literature that lifestyle education and modification initiatives can have multiple benefits in relation to type II diabetes (Yamaoka and Tango, 2005; Anthony et al, 2004; Cooper et al, 2003; Fox and Kilvert, 2003), but these have to be effective and suit those involved.
Gaede et al (2001) carried out a randomised intervention study in this area, and found limited impact of lifestyle education in patients with Type II Diabetes, perhaps due to the lack of an individualised approach. What Gaede et al (2001) show as most difficult is achieving long term, real behaviour and lifestyle changes.
This would require an individualised form of health promotion and disease management, which would take into account all the clinical evidence about pathophysiology and treatment modalities, whilst being modified to meet the specific needs of the individual client in terms of, for example, learning style, previous knowledge, and restrictions on lifestyle such as income or occupation. Anthony et al (2004) argue that the literature supports this approach, and that in order for diabetic clients to fully achieve the lifestyle changes required to reduce the risk of coronary heart disease, they need to properly understand the disease and its consequences, and feel empowered and committed to changing behaviours and embracing health-enhancing lifestyles. According to the literature, health education and intervention strategies would have to promote health through evidence and scientific knowledge whilst also respecting individuals’ self-perceived needs, preferences and choices (Cooper et al, 2003). The most important element of this might be the patient, who must play an active part, but which requires therefore an effective and positive relationship between the patient and the healthcare providers (Cooper et al, 2003). Again, the nurse is in a strong position to achieve this relationship.
Nurses are ideally situated to provide input that empowers patients and promotes self-efficacy, but need to be able to translate the scientific information, such as the studies critiqued within this paper, into terminology which the clients understand and which is relevant to them.
Nurses can also act as the hub in the wheel of multi-disciplinary, collaborative care, engaging with diabetic specialists, medical colleagues, dieticians, and other specialists such as cardiologists and health promotion specialists, to ensure a coordinated, consistent approach to care design, planning, management and delivery. In particular, dietician involvement is vital, particularly in designing individualised and realistic lifestyle changes to support longer term risk reduction (Pollom and Pollom, 2004). However, managing weight loss is more problematic for diabetic patients because of the nature of their condition, because dietary modifications can quickly result in a loss of diabetic control, and if calories are severely restricted, diabetic patients can suffer hypoglycaemia (Watkins, 2003). Dietician and nurse collaboration can design weight loss programmes which help patients maintain steady carbohydrate intakes each day and so prevent wide variations in blood glucose. (Watkins, 2003). However, the way to promote regular physical activity (Vuori, 2001), is not so clearly cut, as there are not really ‘exercise’ healthcare professionals who can be involved in a similar way. It does seem that this is a shortfall, and how nurses can engage clients in healthcare activity needs much more investigation and consideration. One way of achieving this might be to look at nursing principles of health promotion as well as generic principles, and devise a strategy which uses both – a client centred approach with the added weight of professional knowledge and perhaps staged elements, including in-built evaluation (Alfaro-Lefevre, 2006).
There is evidence within the literature to show that the kinds of interventions already developed to bring about lifestyle changes can have a significant effect on health of all clients, and can even serve to halt or slow the progression of disorders such as impaired glucose tolerance to diabetes (Fox and Kilvert, 2003), which would mean that nurses have a role in expanding their work to all potentially at risk clients within the primary care sector. This could be considerably challenging, given the large numbers of clients and the fact that they may potentially not have much contact with healthcare services.
There is a need for a coordinating professional or lead professional in such circumstances (Scott, 2006), and the nurse may be the best person to do this as the one who most consistently and frequently sees the patient. According to Keen (2005), there is an ongoing a need for a properly integrated multidisciplinary approach to diabetes, and sharing and communication between primary healthcare providers and those within the acute care sector. There should be diabetic specialists working within the acute and ongoing care sectors simultaneously (Keen, 2005). Pollom and Pollom (2004) show that if diabetic patients receive seamless care, there can be positive outcomes such as reduction in the length of hospital stay and a reduction in readmissions due to ineffective self-management of their condition. Despite a growing awareness of the need to reduce future healthcare burden by proper chronic disease management in areas such as this, the literature suggests that the multidisciplinary services accessed by diabetic patients are not meeting the targets set (Edge et al, 2005). This may partly be due to the gap between acute and chronic care sectors, because although much diabetic care occurs in the acute care sector, community support and education programmes are those which are most likely to work to support lifestyle changes for these patients (Robinson, 2006).
Nurses have a practical role in promoting good glycaemic control, in ensuring patients can calibrate and monitor their glucose testing equipment, and reinforce the underlying mechanisms of control of blood sugar (Reinauer, 2002). But nurses can also play a significant part in addressing the psycho-social aspects of their patients’ condition, and in assessing the behaviours or psychological responses which may be affecting how patients manage and cope with their ongoing (Watkins, 2003). There is some evidence to suggest that psychiatric, emotional and psycho-social disorders can underlie badly-controlled diabetes, highlighting the psycho-social elements of disease management discussed above, and which are not necessarily adequately addressed in the scientific literature (Watkins, 2003). The nurse can provide, or at least coordinate, social, mental health or other support systems for these patients.
Therefore, this review seems to show that if nurses are armed with the correct, up-to-date information and understanding of the disease processes which link diabetes and coronary heart disease, they can take on leadership roles in health promotion and disease prevention. General lifestyle changes, in the general population, would be one element of their role, alongside specific, targeted, individualised programmes for patients with diabetes, for patients with insulin resistance, and for patients who are identified as at risk of developing type 2 diabetes and insulin resistance. However, current healthcare systems do not support nurses taking such central roles, either in equipping them with the skills and support to appraise the specialist scientific evidence, or in providing them with opportunities to take on leadership roles as part of standard nursing practice. A nursing model of disease prevention in relation to diabetes and risk of coronary heart disease would need to be defined, implemented and tested in order to bring about much-needed changes in approaches to care. This might represent best use of available resources rather than posing a new demand on the rapidly dwindling resources available with the UK National Health Service.
Conclusion and Recommendations for future best practice in the care of patients with diabetes and coronary heart disease.
While this critical review has demonstrated the significant correlation between diabetes and cardiovascular disease risk, it has also show that there is a need for better understanding of the specific underlying mechanisms which contribute to these diseases and to develop evidence-based practice that is founded on this understanding. All of the five primary research articles shed light on the underlying physiological mechanisms and clinical markers of the diseases, showing that not only do they share common antecedents, but that levels of risk are increased in the presence of diabetic disease. All five primary articles are quantitative, scientific and clinically-oriented research studies, a feature which adds to their weight in terms of providing evidence for practice, but may also represent a limitation in terms of understanding any psychosocial factors which affect the disease. For example, none of the studies take into account stress levels as a variable in the development of coronary heart disease, but look at only clinical markers such as obesity or cholesterol levels, for example. Avogaro et al (2007), for example, take into account lifestyle factors, but these are related to smoking behaviours and consumption of alcohol, not psycho-social variables. Disregarding the psycho-social factors which present as risks for the development of either disorder is a serious failing and means that significant information on prevention and treatment may be overlooked. Nursing practice, with its more holistic focus, can address psycho-social dimensions of health and disease, but not without a solid evidence base. Stress is known to mediate the effects of insulin and glucose metabolism, and to contribute to cardiovascular disease, yet none of the primary studies included in this review deal with this. This could be a weakness of this review, and its primary limitation. This author would suggest that future scientific studies should include some measures of stress evaluation, and some inclusion of psycho-social variables.
Another potential limitation of this critical literature review is that the majority of the five primary research articles critiqued focused on type 2 diabetes. This does reflect the fact that this is the most prevalent form of the condition, and that it is also the form most readily associated with cardiovascular disease risk, perhaps due to its association with overweight and obesity. The focus on type 2 diabetes may be related to clinical need to address disease management and preventive strategies for this client group. Certainly the connection between rising levels of obesity, sedentary lifestyles and the increased rates of type 2 diabetes in Western populations require targeted resources, interventions and a consolidated effort to bring about the mangy changes that would be needed to reverse this trend.
One area of practice which could be improved by understanding the physiological and genetic mechanisms which connect these two disorders is in the awareness of causality in this disease, which in turn might serve to change negative stereotypes and attitudes towards people with these diseases. Bowden et al (2006) have explored the genetic foundation for the disorders, and suggest a potential genetic linkage which, if proved by further research, would not only support those with the disease but help prevent a culture of blame which is, unfortunately, emerging in UK health and social care in the wake of recent socio-political trends.
There is also a need for future studies to build on the available evidence, and to learn from the methodological limitations of a lot of the studies which address this linkage between diabetes and cardiovascular disease (Goldfine and Beckman, 2008).
ESC and EASD (2007) show that in terms of cost of diabetic disease, it is not the diabetes itself that causes the increased cost and drain on healthcare resources, but the complications of the disease, especially as these complications result in hospital admissions which are typically of longer duration and related to complex co-morbidities. Therefore, achieving cost effective healthcare may be related not only to the clinical costs but to the preventive activities which all healthcare professionals can engage in. Nurses have a significant role to play in prevent of cardiovascular disease, diabetes, diabetic complications and serious morbidity, but there should be more recognition of this role, more support for nursing interventions which address the psycho-social elements of the diseases as well as the biological and pharmacological elements, and more resources which address intervention early on. While UK governmental drivers advocate for healthier lifestyles, it is important to not blame the victims, but rather to empower them to make the incremental changes which could significantly reduce their risk of morbidity and mortality.
There is no doubt that there is a correlation between diabetic disease and coronary heart disease, although the exact mechanisms and nature of causality remain questionable. The focus of healthcare in the future should be in prevention, early treatment and management, holistic approaches which include the patient as a key player in all aspects of care, and on research which can continue to identify the physiological, genetic and other factors which contribute to these diseases. This review has demonstrated that there is good, scientific research in this area, but it does not address all the issues and does not provide all the answers. Until more is known about this correlation, nurses should be supported to help clients take charge of their own lives, and bring about the changes which have been proven to reduce the risks of developing cardiovascular disease. Nurses may be the key to unlocking this gateway to a healthier future.
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