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Chapter 5

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Biomedical Physio & Kines
BPK 140
Michael Walsh

1 KIN 140 Section 5 Dr Mike Walsh CHRONIC DISEASES (Rust of Our Body) Chronic diseases are diseases that progress very slowly, often for more than 20 years before the body finally succumbs. Often these diseases were not as prevalent in past history because we died of other things sooner before a chronic disease could fully bloom. In addition, some things we have today, like pollution and super size fries, our bodies have never been prepared for. Such an attack upon our physiology becomes a chronic disease. We can usually treat the conditions of a chronic disease but we cannot cure it. Always remember, we are designed by evolution. Chronic diseases account for 75 % of the mortality currently in our Canadian society. The chronic diseases below all have associated risk factors determined from epidemiological studies. Some of the risk factors are immutable (cannot be changed) such as age, gender, and genetics whereas others are mutable such as diet and exercise. I. Cardiovascular Disease A. Definition Cardiovascular disease encompasses any disease of the heart or blood vessels. Arteriosclerosis is a hardening of the arteries and atherosclerosis is a type of arteriosclerosis. Atherosclerosis is a fatty plaque accumulation that occurs at the inner most layer of a blood vessel: the endothelium. Atherosclerosis is the leading killer of cardiovascular disease. If it occurs in the heart, it is called coronary heart disease. If it occurs in the brain it is called a stroke, and if it occurs in a limb it is called peripheral vascular disease. The heart locus accounts for over 2/3 of atherosclerosis. B. Generic Mechanism In atherosclerosis, a lesion occurs on the inner lining of an artery. This leads to an accumulation of lipids creating a fatty streak. Proliferation of smooth muscle cells can occur further narrowing the blood vessel. Calcium and fibrous tissue invade the lipids and it becomes hardened. Blood clotting factors can also invade the fat forming a thrombus which can create a serious blockage of blood flow. Tissues downstream of the artery will suffer ischemia and can die. A piece of the thrombus can break off creating an embolus that will block a vessel further downstream. C. Risk Factors 2 1. Immutables a. Age The risk of atherosclerosis is 3x higher at 60 than 45 yr. This of course is partly due to the chronic nature of the disease progressing with time. It also reflects that as one ages, the repair mechanisms do not work as well. b. Gender Estrogen, a female sex steroid, is believed to have protective effects. c. Genetics/Race Family history plays an important role in CVD. In BC, the Medical Services Commission will normally only reimburse for a total cholesterol test and not for different lipoprotein fractions. If your total cholesterol is lower than 5.2 mmol/L (200 mg %) for under 30 yr and lower than 6.2 mmol/L (240 mg %) for over 30 yr, you only get a paid test every 5 years. If you are above these levels, MSC will pay for more frequent and specific testing. Males of African descent have a higher incidence of CVD, especially if they have hypertension 2. Mutables a. Hypertension Hypertension, or high blood pressure, is a disease in and of itself. Normal blood pressure is about 120 mm Hg/80 mm Hg. Hypertension is often said to exist when blood pressure is >140/>90. We only know about 10 % of the causes of hypertension but we do know that if you have hypertension, the chances of getting atherosclerosis increases dramatically. The abnormally high blood pressure levels create a lot more work for the heart to perform and changes blood flow patterns. Hypertension is enhanced by salt intake. b. Type 2 Diabetes see III. Diabetes c. Diet High fat, high alcohol, high simple sugars, low fibre, low antioxidants, and excessive calories are all thought to contribute to atherosclerosis. 3 Cholesterol is transported in the blood by lipoproteins. These molecules have various amounts of lipid and protein in them: the greater the density, the greater the relative amount of protein. Density is used to classify groups of lipoproteins. We will just classify 2 groups: low density lipoproteins (LDL) and high density lipoproteins (HDL). LDLs transport cholesterol from the liver to the rest of the body and HDLs transport cholesterol from the body back to the liver. A high ratio of LDL/HDL is a risk factor for atherosclerosis even if total cholesterol is under the age-specific limit. If you have too much LDL, it gets deposited in the fatty plaques in the arteries. Often people are asked to reduce their dietary cholesterol. This is good advice if you are cholesterol sensitive, but only about 30 % of people are. Therefore, for most people can decrease their intake of eggs, organ meats, and shellfish with very little effect on the plasma cholesterol levels. Furthermore, for the average person, their liver makes about 80 % of their plasma cholesterol; only about 20 % comes directly from dietary intake. In cholesterol-sensitive people, the liver does not respond ‘normally’ to an increase in dietary intake. Their liver continues to make cholesterol rather than reduce its production Reducing a high fat intake is a good idea, especially saturated fats. The relation between percent of calories from saturated fats and either CHD death rates or serum cholesterol is about 0.85. A moderate consumption of alcohol is associated with higher HDL and reduced heart attacks. High levels of plasma homocysteine (an amino acid) are correlated to arteriosclerosis. More recent evidence indicates this may be due low levels of B vitamins and folic acid. d. Physical Activity Lack of physical activity can lead to diabetes, hypertension, and an increase in the LDL/HDL ratio. Research shows physical activity increases the branching of the arterial tree. Thus if an arteriole becomes block, another arteriole will be in close proximity and can supply the endangered downstream tissue. e. Central Obesity Having fat located on your abdomen (e.g., beer gut for males) is associated with a higher risk of atherosclerosis than having fat located on other parts of your body. Although there are different patterns of obesity, the abdominal pattern is more often associated with males than females. 4 f. Type A Personality A person with a type A personality is one who is quite hard-driving, intense, and competitive. People with type A personality have a greater chance of suffering atherosclerosis that those with a type B personality. g. Other Psychological Stressors Isolation, pessimism and repressed emotions (type D) and people with low self-esteem and confidence also have a greater incidence (3x) of atherosclerosis. h. Smoking Smoking leads to a decrease in HDL and an increase in platelet stickiness. Furthermore, the carbon monoxide produced binds to hemoglobin with 250x the affinity of oxygen. Second hand smoke is unfiltered and thus is more cardiotoxic than the smoke that goes inside a smoker’s lungs. Smoking as a risk factor is interesting. Some people have smoked 3 packs a day for 70 yr and have never had a heart problem. People use such individual-type evidence to show that a relation between smoking and atherosclerosis does not exist. This type of evidence has been used to discount many other types of health problems. However, in this case, what is true for the individual is not true for the population i. Infection Infection with chlamydia pneumonia, H. pylori, and herpes simplex leads to greater heart problem risk. In general, it is found that people with a high level of inflammation as determined by a high white blood cell count have a higher risk of heart disease. D. Prevention Identification of high risk individuals and putting them on a proper prevention program is very important for extending the health of the high risk individual. Such a program could include avoiding tobacco and regular exercise. A healthy heart diet will include replacing saturated fat with unsaturated fat, high fibre content, lots of fruit and vegetables, reducing salt (i.e., help reduce hypertension for some), and omega-3 fats (fish oil). Do what you were designed to do! II. Cancer A. Overview 5 Cancer is a term for a group of over 200 diseases that are characterized by uncontrolled cell growth. Cancer accounts for about 25 % of deaths in our society. A tumor or neoplasm is an abnormal increase in cell division. The tumor can be either benign or malignant. A benign tumor (is not a cancer) usually does not present any health problems other than size related ones. A malignant tumor is a cancer and can spread to other tissue beds by 2 mechanisms: direct invasion of malignant cells into neighbouring tissues or by metastasizing in which malignant cells enter the blood or lymph and then can enter other tissues. B. Causes One reason there are so many different diseases that characterize cancer is that u
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