Magoosh GRE

Chronic Stress and Coronary Heart Disease

| March 24, 2015

Assess the role of chronic stress in the development of coronary heart disease

The heart is a vital muscle which is responsible for pumping blood around the body. It receives its own supply of blood from coronary arteries which are a network of blood vessels located on the surface of the heart. When the blood supply is blocked or disrupted due to accumulation of fatty substances in the coronary arteries, the term used to describe what happens is known as coronary heart disease.1
Coronary heart disease is the cause of about 94,000 deaths in the UK each year and an estimated 2.6 million people are living with the condition and angina which is the most common symptom of coronary heart disease.1it is often triggered by physical activity or stressful conditions. Other symptoms of coronary heart disease include myocardial infarction which occurs when the coronary arteries becomes completely blocked and heart failure which could either be acute, occurring suddenly or chronic, occurring gradually overtime.2
Coronary heart disease is caused by a process known as atherosclerosis. This is the build up of atheroma (cholesterol and other waste substances) on the walls of the coronary arteries thereby reducing the flow of blood to the heart. Individuals who smoke, have a high blood cholesterol, high blood pressure, diabetes, lack physical activity, are obese or have a family history of coronary heart disease have a significant increased risk of developing atherosclerosis.(3)
Stress occurs as a result of not being able to cope under pressure. It can affect individuals of all ages and gender and has the ability to lead to physical and psychological health issues.4Common causes of stress include money problems, death of a loved one, job worries, relationships and exams.5 Chronic stress occurs as a result of prolonged exposure to these common causes of stress. Although some stresses can work to our advantage at times by creating a boost that provides the drive and energy needed to help get through situations like exams or work deadlines, a tremendous amount of stress can have health consequences and adverse effects on the neuroendocrine, cardiovascular, immune and central nervous systems.6
When the body undergoes excessive stress, the hypothalamus in the brain is stimulated and this activates the fight of flight response triggering the production and release of chemicals such as adrenaline, noradrenaline and the primary stress hormone cortisol. Chronic stress over activates the fight or flight response and causes the accumulation of excessive stress hormones which if not metabolised properly overtime can cause disorder of the autonomic nervous system leading to headache, high blood pressure, irritable bowel syndrome and also disorders of the immune and hormonal system creating increased likelihood of having an infection, chronic fatigue and depression.7
Chronic stress contributes to many of the factors that increase the likelihood of developing atherosclerosis and therefore coronary heart disease. An example is high blood pressure. Studies have reported an association between stress and hypertension (high blood pressure). People who frequently experience sudden increases in blood pressure caused by mental stress may, over time, develop injuries in the inner lining of their blood vessels. If left untreated, hypertension can lead to different types of cardiovascular disease such as an heart attack5. In one 20-year study, for example, men who regularly measured highest on the stress scale were twice as likely to have high blood pressure compared to those with normal stress8.
Another risk factor which contributes to the development of coronary heart disease is smoking. The usual explanation for the relationship between smoking and stress is that smoking relieves stress. When smoking, the smoker feels relaxed, however without nicotine, they feel tense. Contrary to the traditional explanation, smoking is not relaxing. Evidence has shown that smoking actually causes stress instead of reducing it8. For people undergoing stress, tobacco and cigarettes is seen as a way of helping them cope with the strains of everyday life. If going under chronic stress, they will frequently seek relief through cigarette use, when they are deprived of nicotine, stress increases and so does the tendency to smoke. This creates a cycle of dependency9, the individual will smoke more often thereby increasing the likelihood of coronary heart disease development.
Stress is often related to weight gain and obesity. When undergoing stress, many people reach out to fatty, salty and sugary foods to counteract the tension and hence the weight gain. The release of cortisol which is a major stress hormone while undergoing stress promotes abdominal fat and could possibly be the link between stress and weight gain. Chronic stress leads to the body tissues being exposed to high levels of cortisol for extended periods of time. As a result, some cellular and tissue alterations may occur, stores of fat and excess circulating fat are relocated and deposited in the abdomen and if left unchecked can develop into obesity. Additionally, high levels of cortisol has also been linked to high blood pressure, hyperlipidaemia and hyperglycaemia which are significant risk factors for the development of coronary heart disease.10
Susceptibility to diabetes or having diabetes is an additional risk factor of coronary heart disease. Chronic stress has been linked with the progression of insulin resistance which is a condition where the body cannot effectively control blood sugar levels9. The psychological response to stressors of various types leads to the activation of the hypothalamus- pituitary adrenal axis. Constant activation leads to various endocrine abnormalities such as low sex steroid and high cortisol levels that antagonize the actions of insulin11. Insulin-resistance is a primary factor in diabetes9. Evidence suggests that stressful experiences might affect diabetes, in terms of both its onset and its exacerbation affecting the patient’s ability to manage the disease efficiently11
Coronary heart disease is much more common in individuals subjected to chronic stress. Research has focused on how to identify this growing problem, particularly with respect to job stress. In June 2002, a prospective cohort study within the Whitehall II study was carried out by Kuper and Marmot to study the link between job strains and coronary heart disease risk. The participants of the study were staff from a London based office in 20 civil service departments and consisted of 6895 males and 3413 female civil servants between the age of 35 and 55. During the first phase of the study, self reported psychosocial work characteristics data was received from each participant. Follow up was till the end of phase 5 with a mean length of 11 years. The results of this study suggests that individuals with job strain, high job demands and low decision altitude have an increased risk of coronary heart disease.12

An article on a clinical research by the European society of cardiology discussed the association between work stress and coronary heart disease. The research’s aim was to investigate the behavioural and biological factors linking stress at work with coronary heart disease. It consisted of a total of 10,308 male and female participants who were exposed to work stress and data on behavioural risk factors, the metabolic syndrome, heart rate variability, morning rise in cortisol and incident of coronary heart disease on the basis of coronary heart disease death, angina or non-fatal was collected. The results to the research stated that cumulative work stress is a risk factor for coronary heart disease and has direct effects on the neuroendocrine stress pathways. This link between work stress and coronary heart disease was seen particularly in the younger working age population i.e employees younger than 50 and still in employment. The study also showed that 32% of the effect of work stress on coronary heart disease is due to the impact of work stress on health behaviours such as lack of physical activity, increase in alcohol and nicotine intake and poor diet13.
Metabolic Syndrome is the name used to describe a group of risk factors that increase the risk of developing coronary heart disease. In order to be diagnosed with metabolic syndrome, an individual must have at least three of the following metabolic risk factors; a large waistline, high blood pressure, high triglyceride level, low HDL cholesterol level and high fasting blood glucose level.14 the results to the study carried out by the European society of cardiology investigating the association between work stress and coronary heart disease also showed that 16% of the effect of work stress on coronary heart disease can be explained by the consequence of work stress on the metabolic syndrome13.
In 2009, the Stockholm Women’s Intervention trial for coronary heart disease took place. The intervention carried out a stress reduction program for women and investigated the ability of stress reduction to extend the lives of women with coronary heart disease. The participants were two hundred thirty-seven women, aged 75 years or younger who were in hospital for acute myocardial infarction, percutaneous coronary intervention or coronary artery bypass grafting. They were separated into two groups, one group received the psychosocial intervention program while the other received usual care. For the group receiving the psychosocial intervention, education was provided about risk factors, training on ways to relax, methods for self monitoring and cognitive restructuring usual care with an emphasis on self care, how to deal with stress from work and family, and being compliant with clinical advice provided. Over a mean of 7 years after entering the study, women in usual care had a mortality rate of 20%, whereas those in the psychosocial intervention had a mortality rate of 7%. The Stockholm Women’s Intervention Trial for Coronary Heart Disease, using a group-based psychosocial intervention program for women with coronary disease, was shown to improve survival.15 This goes to show that cumulative stress plays an important role in the development of coronary heart disease as its control made a difference to survival rates.
People react differently to stress. There has been evidence suggesting that the individual could be the cause of the problem rather than the stress. Type A behaviour pattern refers to a number of personality trait characteristics such as impatience, ambitious and competitive behaviour, intolerance, hostility and anger. These individuals are at a higher risk of coronary heart disease compared to individuals with type B personalities who are patient, non-competitive, and time-insensitive. In 1974, Friedman and Rosenman studied 3200 healthy American men to investigate the connection between stress and coronary heart disease. A follow up after eight and a half years identified two hundred and fifty seven men who had developed coronary heart disease. Seventy percent of these men had Type A personality.16
A case control study using the Chinese population also investigated the association between level of job stress and coronary heart disease. The participants were three hundred and eighty eight people aged between thirty and seventy receiving coronary angiography for suspected or known ischaemic heart disease. The effort reward imbalance was used to measure job stress before the onset of coronary heart disease. The results show that in the Chinese population, individuals who reported a high effort reward imbalance and high level of over commitment had a threefold higher risk of coronary heart disease than those with a low level of over commitment. This shows that job stress significantly increases the risk of coronary heart disease and could be a vital risk factor independent of the other traditional risk factors of coronary heart disease.
Overall it can be seen that chronic stress

plays a contributory role to the development of coronary heart disease by enhancing significant risk factors such as high blood pressure, high cholesterol, diabetes, smoking, weight gain and lack of physical activity.

REFERENCES
1. National Health Service. Coronary heart disease . Available: http://www.nhs.uk/conditions/coronary-heart-disease/Pages/Introduction.aspx. Last accessed 4th Aug 2011.
2. National Health Service. Coronary heart disease . Available: http://www.nhs.uk/conditions/coronary-heart-disease/Pages/symptoms.aspx. Last accessed 4th Aug 2011.
3. National Health Service. Coronary heart disease . Available: http://www.nhs.uk/conditions/coronary-heart-disease/Pages/causes.aspx. Last accessed 4th Aug 2011.
4. American Psychological Association. Understanding Chronic Stress.Available: http://www.apa.org/helpcenter/understanding-chronic-stress.aspx. Last accessed 4th Aug 2011.
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6. Anderson, N.B. (1998). “Levels of Analysis in Health Science: A Framework for Integrating Sociobehavioral and Biomedical Research,” Annals of the New York Academy of Sciences, Vol. 840, pp. 563-576.
7. Neil F. The fight or flight response. Available: http://www.thebodysoulconnection.com/EducationCenter/fight.html. Last accessed 5th Aug 2011.,
8. Andy C Parrot. (1999). Does cigarette smoking cause stress. American Psychologist. 54 (10), 817-820.
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10. Christine A. Maglione-Garves, Len Kravitz, Ph.D., and Suzanne Schneider, Ph.D. (2002). Cortisol Connection: Tips on Managing Stress and Weight. 34-37.
11. Cathy Lloyd Phd, Julie Smith Bsc, RGN, Msc and Katie Weigner. (April 2005). Stress and Diabetes: A Review of the Links. Diabetes Spectrum. 18 (2), 121-127.
12. H Kuper, M Marmot. (2003). Job strain, job demands, decision latitude, and risk of coronary heart disease within the Whitehall II study. Journal of Epidemiology and community health. 57 (2), 147-153.
13. Tarani Chandola , Annie Britton , Eric Brunner , Harry Hemingway , Marek Malik , Meena Kumari , Ellena Badrick , Mika Kivimaki , and Michael Marmot. (2008). Work stress and coronary heart disease: what are the mechanisms? European Heart Journal, 1-9.
14. National heart lung and blood institute. (2006). Metabolic syndrome.Available: http://www.nhlbi.nih.gov/health/dci/Diseases/ms/ms_whatis.html. Last accessed 6th August 2011.
15. American Heart Association. (2009). Stress Reduction Prolongs Life in Women With Coronary Disease. Circulation: Cardiovascular Quality and Outcomes. 2, 25-32.
16. Psychlotron. Stress-CHD-Personality. Available: http://blogs.thegrangeschool.net/psychology/files/2011/02/chd-and-stress.pdf. Last accessed 7th Aug 2011.
17. Weixian Xu, Yiming Zhao, Lijun Guo. (2009). Job stress and coronary heart disease-a case control study using chinese population. Journal of occupational health. 51 (2), 107-113.

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