Risk factors for Heart Disease

Risk factors for heart disease150-162

A ‘risk factor’ may be defined as any habit or feature that can be used to predict an individual’s probability of developing that disease.

Blood cholesterol and Heart disease

Blood cholesterol and lipoproteins- an overview163-178
  • Cholesterol is a kind of fat which has several important functions in the body.
  • Lipoprotein is a vehicle for cholesterol transport in the blood.
  • The two types of lipoproteins that carry cholesterol to and from cells are low-density lipoprotein, or LDL, and high-density lipoprotein, or HDL.
  • LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C), along with VLDL (one fifth of your triglyceride level), make up your total cholesterol count, which can be determined through a blood test.
  • Lipoproteins like LDL and VLDL are nicknamed as bad cholesterol because they have a tendency to stick to the blood vessel wall and form a fatty deposit called plaque.
  • As the plaque builds up, it narrows the blood vessel which is no longer flexible and elastic. It becomes difficult for the heart to pump blood through such a blood vessel and hence there is an increase in blood pressure and heart disease risk.
  • HDL nicknamed as good cholesterol is a lipoprotein which clears off fatty deposits from the blood vessel thus rendering protection from heart disease.
  • The fat we eat gets digested in the body and travels to various parts through the blood. Triglyceride is the major form of fat that travels in the blood immediately after a meal. Excess of triglycerides get stored in the body. A stored triglyceride is an ATM which provides fat and glucose whenever the body demands for. Excess of carbohydrates and fat through your meal can cause an undesirable rise in the blood triglyceride levels, increasing your risk for obesity, diabetes and heart disease.
  • If your blood cholesterol test report reads any of the following that is, Total cholesterol above 200 milligrams, LDL above 100 milligrams, HDL below 40 milligrams and triglyceride levels above 150 milligrams per 100ml of blood in the fasting state then it is indicative of dyslipidemia (abnormal circulating levels of lipids/lipoproteins in blood).
  • Serum lipid ratios, namely total cholesterol (TC) to HDL-C ratio (TC:HDL), LDL-C:HDL-C ratio and triglyceride (TG) to HDL ratio (TG:HDL) are also good indices for predicting heart disease risk.
What percentage of heart disease risk is contributed by blood cholesterol & triglyceride fractions?179-203
  • Although a total cholesterol level less than 200 mg/dl is generally considered a desirable level, this is not the case for Asian Indians for whom the desirable level is 20% lower or less than 160 mg/dl.179-182
  • A 40 mg/dL lower cholesterol level was associated with about 56% lower CAD (Coronary Heart Disease) mortality at ages 40-49, in both sexes but decreases to 34% at ages 50-69, and to 17% at ages 70-89 years.183-184
  • Every 10 mg/dl increase in serum total cholesterol concentration increased the total mortality rates by 5%.185
  • LDL-C carries cholesterol towards the arteries and heart. It is nicknamed as bad cholesterol since it can clog blood vessels and makes them less flexible, increasing the risk for blood pressure elevation, excess inflammation and eventually heart disease.186
    • A 10-mg/dL increase in LDL cholesterol was associated with a 12% increase in CVD risk.
    • According to renowned Health organizations including the American Heart Association, World Health Organization and National Cholesterol Education Program standards, an LDL-C value below 100 mg/dl is considered as favourable for heart health.
    • LDL-C >130 mg/dl requires lifestyle modification (along with drug treatment, if need be, based on physician’s advice). According to the CADI (Coronary Artery Disease in Asian Indians) research, for every 1 mg/dL increase in LDL-C, the relative risk for coronary heart disease increases by 1%. A 50 mg/dL decrease in LDL-C results in 32% reduction in heart attack and 20% reduction in stroke.
  • HDL is considered as good cholesterol as it carries excess cholesterol away from the blood vessels (and heart) and towards the liver for breakdown.
    • According to the CADI research, a 1% increase in HDL-C confers a 2% decrease in heart disease risk and a 1 mg/dL decrease confers a 4% increase in CVD risk.187-188
    • In the Framingham Study, risk for CAD increases sharply as HDL levels fall progressively below 40 mg/dL.189
    • In the Quebec Cardiovascular Study, for every 10% reduction in HDL, risk for CAD increased 13%.190
  • The risk of CHD, with increasing serum triglyceride level was much steeper in women than in men191-192
    • For each mg/dl rise in serum triglycerides, CHD risk increases by 14 per cent in men and 37 per cent in women.193
    • An increment in the serum triglyceride level above 190 mg/dl increased the CHD risk by 75 per cent in women versus 30 per cent in men.194
  • Non-HDL-C represents the cholesterol content present in all the atherogenic lipoproteins (that is, lipoproteins that are potent in causing a fatty deposit in a blood vessel). Non-HDL-C is calculated by subtracting the good cholesterol portion (that is, HDL-C) from total cholesterol
  • Lipoprotein(a) is a strong, causal risk factor for heart attack and stroke. Lp(a) is a genetic variant of LDL particle with one molecule of apolipoprotein B100 (apoB) and an additional protein, apo(a), attached via a disulphide bond
    • Lp(a) levels are high in people with a family history of early heart disease.
    • High Lp(a) levels confer a 2-4-fold risk of first or recurrent heart attack and/or stroke.
    • Lp(a) levels >30 mg/dL is an independent risk factor for premature CAD with risk comparable in magnitude to a total cholesterol level of >240 mg/dL or an HDL-C level of <35 mg/dL. The risk increases to 25-fold in those who have all three of these lipid abnormalities.
    • Lp(a) is particularly dangerous among Indians due to common occurrence of high TC/HDL ratio.
Scientific facts relating serum lipid ratios with heart disease204-207
  • A triglyceride to HDL-C (TG:HDL-C) ratio of > 3.5 is a strong indicator of the presence of insulin resistance
  • According to the American Diabetes Association, a 1.7 increment in total cholesterol to HDL-C ratio is shown to increase the risk of diabetes by approximately 14%.
  • A high LDL/HDL cholesterol ratio poses a greater cardiovascular risk owing to the imbalance between the cholesterol carried by harmful (atherogenic, that is, heart disease-causing) and protective lipoproteins.

Blood Pressure and Heart disease208-218

  • Blood pressure measures the force of the blood against the artery walls. If the pressure is too high (hypertension), it weakens the blood vessels and strains the heart because it must work extra hard to get the oxygenated blood to the rest of the body.
  • Blood pressure is determined by the amount of blood pumped by heart and the resistance to blood flow exerted by blood vessels (mainly arteries).
  • Narrower the space in blood vessels, greater is the resistance to blood flow & henceforth a higher blood pressure.
  • Sustained increase in blood pressure can lead to blood vessel damage or other detrimental health effects.
  • Important components that vitally regulate blood pressure include blood vessel wall tone, release of components that constrict/dialate blood vessels, new blood vessel formation (angiogenesis) and fluid & electrolyte balance mainly through sodium reabsorption.
  • Systolic blood pressure is the amount of pressure generated by the heart when it contracts and pumps out blood to the body parts.
    • Systolic blood pressure measures the pressure in the arteries when the heart beats (contracts to pump out blood)
  • Diastolic blood pressure is the amount of pressure felt in the arteries when the heart rests between beats.
    • Diastolic blood pressure measures the pressure in the arteries when the heart muscle is resting between beats and refilling with blood
  • Recent international hypertension guidelines, including the New International Classification of Diseases: ICD-10 (2012) have created categories below the hypertensive range to indicate a continuum of risk with higher levels of blood pressure in the normal range.
  • Based on the Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, JNC7 (2003) in people aged 18 years or older, systolic blood pressure in the range of 90 to 119 mm Hg and diastolic blood pressure in the range of 60 to 79 mm Hg is termed normal, while the term prehypertension is used for blood pressure in the range 120 to 139 mmHg systolic and/or 80 to 89 mm Hg diastolic (Chobanian et al., 2003; Williams et al., 2004; Giles and Sander, 2012).
  • Hypertension is defined as ≥140 mmHg systolic and/or ≥90 mm Hg diastolic.
    • Stage 1 hypertension is systolic blood pressure in the range of 140 to 159 mmHg or diastolic blood pressure in the range of 90 to 99 mmHg.
    • Stage 2 hypertension is systolic blood pressure ≥ 160 mmHg or diastolic blood pressure ≥ 100 mmHg.
    • Hypertensive crisis (emergency care needed) is when systolic blood pressure is higher than 180 mmHg or diastolic blood pressure is higher than 110 mmHg.
  • According to WHO (2005) lipid abnormalities are four times more common in hypertensives than in normotensives.
  • Hypertension in premenopausal women increases the risk for CHD death as much as ten times, and among the elderly it is a stronger CHD predictor in women than men.212

Inflammation and Heart disease219-237

Inflammation- an insight
  • Inflammation can be defined as the response given by our body to any infection, injury or any other internal abnormality like a hormonal disturbance or a blood vessel rupture.
  • Inflammation is our body’s self-defence mechanism. Or in other words, it is the body's attempt at self-protection to remove harmful stimuli and begin the healing process.
  • The purpose of inflammation is to eliminate the initial cause of cell injury, clear out necrotic (scared or damaged) cells and to initiate tissue repair.
  • Once the purpose of inflammatory trigger is solved, then anti-inflammatory markers of our body come into picture to normalize the inflammatory state.
  • When there is excess inflammation which is consistently ongoing, it can cause health disturbances including heart disease.
  • Abnormal cholesterol in the absence of inflammation rarely causes heart attacks. On the other hand, normal cholesterol levels in the face of rampant inflammation can cause heart attacks and a host of other chronic diseases.
Role of inflammation in atherosclerotic heart disease219-230
  • Inflammatory processes are important contributors to the development of atherogenesis (atherosclerotic/fatty plaque formation in blood vessels) as well as to the vulnerability of atherosclerotic lesions to rupture.
  • The inciting event in many heart attacks and some forms of stroke is buildup of fatty, cholesterol-rich plaque in blood vessels.
  • The body perceives this plaque as abnormal and foreign (as it is not present in a healthy blood vessel). In response, the body tries to wall off the plaque from the flowing blood.
  • However, under the wrong set of circumstances, that plaque may rupture, and its walled-off contents can come into contact with blood and trigger a blood clot formation.
  • The blood clot formation can narrow down the inner space of blood vessel, hindering/occluding the blood flow.
  • Inflammation occurs in the vasculature (blood vessel wall) as a response to injury (internal) and lipid peroxidation (cholesterol components are converted into more harmful forms).
  • Various risk factors are amplified by the harmful effects of oxidized LDL (bad cholesterol gets converted into a form which is more prone to get deposited on blood vessel wall), initiating a chronic inflammatory reaction, the result of which is a vulnerable plaque prone to rupture and thrombosis (blood clot formation obstructing the blood flow in a vessel).
CRP as an inflammatory risk factor for heart disease231-234
  • The most extensively studied biomarker of inflammation in CVD is serum C-reactive protein or CRP.232
  • In 2003, the AHA and the CDC Scientific Statement on inflammatory Markers recognized high sensitivity serum CRP as a useful marker of CVD risk.233
  • Among apparently healthy men, the baseline level of inflammation, as assessed by the serum CRP concentration, predicts long-term risk of a first myocardial infarction, ischemic stroke, peripheral vascular disease, and all-cause mortality.234
  • According to the AHA and the US Centers for Disease Control and Prevention (CDC), people whose CRP is above 3 mg/L of blood, have around twice the risk of a heart attack compared to those with lower levels.231
  • Based on the American Heart Association (CDC/AHA) Workshop on Inflammatory Markers and Cardiovascular Disease, a homocysteine level above 10 µmol/L indicates a risk for health disturbances related to heart and blood vessels.231
Scientific Facts relating homocysteine with heart health disturbances235-237
  • Homocysteine is a by product of cell metabolism, and has to be eliminated in a timely fashion with the help of B vitamins (especially folate).
  • Excess homocysteine can induce inflammation, damage blood vessels, increase blood pressure and cause a disturbance in heart health.
  • High homocysteine levels in the blood can damage the lining of the arteries, and can make blood clot more easily than it should. This can increase the risk of blood vessel blockages.
  • An epidemiological study has demonstrated that homocysteine levels above 10 µmol/L are associated with an up to three-fold increase in heart attack risk.235
  • The European Concerted Action Project reported more than a doubling of vascular disease when homocysteine levels exceed 12 µmol/L.236
  • Participants whose homocysteine levels were equal to or greater than 12 µmol/L were found to have a 35% mean increase in the progression of coronary artery calcification, compared to a 17% increase in those whose homocysteine levels were below 12 µmol/L.237

Interface of excess weight & blood sugar with dyslipidemia in causing heart disease238-247

  • Overweight is a state in which body weight exceeds a standard based on height (Body Mass Index or BMI in the range of 23-24.9)
  • The World Health Organization defines obesity as a condition of excessive fat accumulation to the extent that health and well-being are affected.238
  • The risk of CHD is over four times higher in women with a BMI of 29 and above compared to those women with a BMI of less than 21.239
  • Central obesity characterized by excessive adipose fat in the abdomen appears to impart a greater risk for CHD.
  • Excess weight in combination with high LDL-C, low HDL-C and elevated homocysteine levels may predispose to an elevation in blood pressure.
  • A 20% increase in body weight above the normal BMI (18.5-22.9) is associated with a two-fold increase in the risk of hypertension.240-241
  • The Nurses’ Health Study has reported that women who maintain their ideal body weight have 35 to 60 per cent lower risk of myocardial infarction than those who exceed it.242
  • Obesity in combination with high triglyceride and low HDL-C levels may predispose to an elevation in blood pressure and excess inflammation, both of which disturb the health of blood vessels and heart.
  • A high triglyceride level in combination with excess weight and impaired glucose tolerance adds on to the severity of blood sugar and heart health disturbances.
  • American Diabetes Association (ADA) recommends "screening of adults for diabetes at any age with BMI≥25 kg/m2, HDL-C level < 35 mg/dl and/or a TG level >250 mg/dl.
  • Low HDL-C is known to be an important predictor for development of diabetes. An increment of 12mg/dl in HDL-C is shown to be associated with a 25 percent lower risk of incident diabetes.
  • A triglyceride to HDL-C (TG:HDL-C) ratio of > 3.5 is a strong indicator of the presence of insulin resistance; Insulin resistance is a key causative factor for blood sugar disturbance and type 2 diabetes.
What is insulin resistance?
  • Glucose, a simple carbohydrate is a major fuel source for our body. Our digestive tract breaks down carbohydrates (sugars and starches) from food sources into glucose. Glucose is a form of sugar that enters the bloodstream.
  • The energy that is required by our body cells for their existence and normal functioning is obtained by breaking down dietary components or glucose stores.
  • There is always a balance maintained between the cellular requirement for glucose and the glucose supply through blood. And this balance is important for deciding glucose levels in the blood.
  • Insulin is an important hormone that takes up the responsibility of maintaining this balance, or in other words it renders blood sugar control. Insulin influences the way our body uses digested food for energy.
  • With the help of the hormone insulin, the glucose in blood enters the cells to suffice their energy need.
  • Insulin resistance is a condition in which the body produces insulin but does not use it effectively. When people have insulin resistance, glucose builds up in the blood instead of being absorbed by the cells, leading to type 2 diabetes or prediabetes.
  • Impaired glucose tolerance/pre-diabetes is defined as having a blood glucose level that is higher than normal, but not high enough to be classified as diabetes.
  • When an early diagnosis of pre-diabetes is made, a majority of beta cells (insulin-producing cells) are functional. Positive lifestyle changes at this stage can preserve the health of beta cells and make blood sugar control easier.

Blood clotting/Coagulation and heart disease248-259

  • All of us have clotting factors in our blood to ensure we do not bleed excessively when there is an injury.
  • But health disturbances like injury in a blood vessel (endothelial dysfunction) arising due to inflammation & fatty deposit (plaque formation) can lead to the development of blood clots.
  • A blood clot forms when blood cells and fibrin strands clump together in response to injury in the innermost layer of a blood vessel wall (endothelial injury).
  • Turbulent blood flow causes endothelial injury. Turbulent blood flow occurs when blood vessels are affected by atherosclerosis, hypertension, abnormal arterial dilations (aneurysms), arterial stiffness or heart valve damage.
  • Thrombosis is the name given to the formation of blood clots.
  • When the clot blocks the blood flow to the heart or the brain, a heart attack or stroke can follow. An embolism occurs when a blood clot travels around the body and lodges in an organ.
  • Blood clots that arise in the arteries of the heart itself may block the flow of blood through that artery and cause a heart attack.
  • Blood clots that arise from within the carotid arteries in your neck may travel to the brain and cause a stroke.