Risk Factors

You can avoid heart disease or stroke by first becoming aware of the risk factors.

 

Factors you can change

This group of risk factors stems mainly from the personal habits and practices which we have cultivated since childhood. Although it is more effective to check the development of unhealthy habits from young than to try and modify such habits later in life, the good news is that it is never too late to start adopting heart-healthy habits so as to reduce your risk of cardiovascular disease.

The main risk factors which fall under this category are:

High Blood Cholesterol

It is generally known that the risk of heart disease rises as a person’s blood cholesterol levels increase. It is, however, important to distinguish in this context the different types of cholesterol found in the human body.

Cholesterol is a soft, fat-like substance used to form certain tissues in the body, especially nerves. Your body derives the cholesterol which it needs from your daily diet. The fat in the food which you consume is digested in the body and taken to the liver, where it is processed into cholesterol.

The two main types of cholesterol are low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol. LDL cholesterol is commonly referred to as “bad” cholesterol because it carries fat from your liver to other parts of the body. The higher the level of LDL in your blood, the greater the likelihood that cholesterol will deposit within the walls of your blood vessels. This in turn increases your risk of developing atherosclerosis.

Conversely, HDL cholesterol is called “good” cholesterol because it is believed to help your body get rid of cholesterol by transporting fat and LDL cholesterol deposits to the liver for breakdown, thereby “cleansing” the arteries.

Thus, to protect yourself against cardiovascular disease, you would want your HDL (good) cholesterol level to be high and your LDL (bad) cholesterol level to be low. An excessive amount of LDL in the blood is a cardiovascular risk factor; likewise if your HDL level is abnormally low.

As a general guide, the average adult should maintain his LDL cholesterol level at less than 3.4 mmol/L (130 mg/dl), his HDL cholesterol level at 1.0 mmol/L (40 mg/dl) or above, and his total cholesterol level at less than 5.2 mmol/L (200 mg/dl). If he has other risk factors for cardiovascular disease, he should aim to keep his LDL and total cholesterol levels even lower at below 2.5 mmol/L (100 mg/dl) and below 4.1 mmol/L (160 mg/dl) respectively. These parameters are summarised in the table below.

Desirable Cholesterol Levels

Cholesterol in mmol/L (mg/dl)Average Adult (without known coronary risk factors)Adult with heart disease / diabetes / other coronary risk factors
LDL Cholesterol< 3.4 (130)< 2.6 (100)
HDL Cholesterol≥ 1.0 (40)≥ 1.0 (40)
Total Cholesterol< 5.2 (200)< 4.1 (160)

Healthy cholesterol levels can be attained by combining a low-fat diet with exercise and weight control.

High Blood Pressure

Blood pressure refers to the force with which your heart pumps blood throughout your body. It varies from person to person. Even for the same individual, blood pressure may vary from time to time when, for instance, when one gets angry versus when one is relaxed.

Blood pressure is expressed as a fraction of two numbers and is measured in mm Hg (millimetres of mercury). The first number is the systolic pressure, i.e. the pressure with which the heart contracts and pumps blood to the rest of the body. The second number is the diastolic pressure, which is registered as the heart relaxes and its chambers open, filling with blood.

In general, blood pressure is classified as shown below:

ClassificationSystolic (mm Hg)Diastolic (mm Hg)
Normal< 130< 80
Pre-hypertensive130-13980-89
Hypertensive≥ 140≥ 90

When a person’s blood pressure is consistently at or greater than 140/90 mm Hg, he is said to have high blood pressure or hypertension.

Hypertension increases one’s risk of cardiovascular disease as the blood vessel walls become irritated by the increased pressure exerted by the blood flowing through. As more and more damage is done to the vessel walls, plaque tends to form, in turn increasing the likelihood of atherosclerosis and coronary heart disease.

In about 5% of hypertensive cases, the cause of elevated blood pressure can be attributed to a specific condition or illness such as kidney disease or a structural abnormality of the aorta. Such cases of secondary hypertension can usually be cured by appropriate medical treatment.

For the majority of hypertensive patients however, no explanation for their high blood pressure can be found. Evidence suggests that this form of hypertension, also known as primary hypertension, is caused by a combination of hereditary and lifestyle-related factors such as excessive salt intake, obesity, and stress.

As with secondary hypertension, primary hypertension can be lowered through medication. Weight reduction, regular exercise, and salt restriction are also essential control measures.

Resources (click to download):
Dr Low Lip Ping’s Presentation @ Down with High Blood Pressure Public Forum 2017

Diabetes Mellitus

Diabetes is a long-term illness characterised by a high sugar (or glucose) level in the blood. Someone with diabetes is either producing too little insulin or is unable to respond well to the insulin produced.

Diabetes escalates one’s risk of developing cardiovascular disease, resulting in approximately two-thirds of diabetics worldwide dying of some form of heart disease or stroke.

Type 1 (insulin-dependent) diabetes

A condition in which there is a total absence of insulin production. This type of diabetes, which usually arises during childhood, is also referred to as “juvenile diabetes”, and is managed by administering regular insulin injections to the patient throughout his life.

Type 2 (adult onset) diabetes

A condition in which the body’s cells are unable to use insulin effectively. The patient is usually treated with oral medications, either with or without insulin injections as an adjunct.
Diabetes escalates one’s risk of developing cardiovascular disease, resulting in approximately two-thirds of diabetics worldwide dying of some form of heart disease or stroke.

According to the American Heart Association:

  • At least 68% of people aged 65 or older with diabetes die from some form of heart disease; and 16% die of stroke.
  • Adults with diabetes are 2 to 4 times more likely to die from heart disease than adults without diabetes.

There are several reasons for this. First, diabetes tends to cause irritation of the blood vessel walls. Second, it appears to increase the level of LDL (bad) cholesterol and decrease the level of HDL (good) cholesterol in the blood. Third, it raises the sufferer’s blood pressure.

Together, these factors result in diabetics having more extensive atherosclerosis and a higher fatality rate from heart attacks than their non-diabetic counterparts of the same age. Measures which can help to bring diabetes under control include weight reduction, following a strict diet, and regular exercise.

Source: American Heart Association

Overweight / Obesity

For a person whose body weight exceeds his recommended weight range by 20% or more, the risk of heart attack is roughly three times greater than that of a person who is within the healthy weight range. This is because overweight and obesity in particular, increases one’s chances of developing other contributory factors for cardiovascular disease.

For instance, weight gain per se has been associated with an increase in LDL (bad) cholesterol and a decrease in HDL (good) cholesterol. Being overweight or obese also raises one’s likelihood of developing high blood pressure and diabetes.

Ideally, your Body Mass Index (BMI) should be between 18.5 and 22.9, as shown in the table below:

BMICategory
< 18.5Underweight
18.5 – 22.9Normal
23.0 – 29.9Overweight
≥ 30.0Obese

Want to know your BMI? Use our online BMI Calculator.

Smoking

Smoking is widely regarded as the single biggest risk factor for cardiovascular disease.

Smokers face approximately twice the risk of having heart attacks than non-smokers. They are also more than twice as likely to meet with sudden cardiac death. The same health risks apply to passive smokers, i.e. people who do not themselves smoke but who are nonetheless constantly exposed to smoke exhaled by others in their proximity.

Smoking is a major cardiovascular risk factor because of the poisonous effects of the chemicals contained in tobacco. For instance, nicotine causes a rise in blood pressure, narrowing of the blood vessels, irregular heartbeats and spasms of the muscles in arterial walls. Similarly, the carbon monoxide in cigarette smoke damages the inner lining of the blood vessels as well as reduces the oxygen level in blood. This irritates the blood vessel walls and may trigger the onset of atherosclerosis.

Quitting smoking, or refraining from the first puff, will contribute significantly to the prevention of heart disease, as well as arrest the deterioration of any existing heart conditions.

Lack of Exercise

Exercise helps to boost the level of HDL (good) cholesterol and reduce the level of LDL (bad) cholesterol in the blood. It also assists in weight control and the promotion of cardiovascular fitness.

Conversely, lack of exercise may double a person’s risk of developing and subsequently dying from cardiovascular disease. This is because a person who leads a sedentary lifestyle is more likely to become overweight and/or have high blood pressure, diabetes, and high LDL cholesterol, all of which adversely affect one’s heart health.

In general, the more vigorous your exercise routine, the more health benefits you derive. However, even exercise at a comparatively low to moderate level of intensity – provided it is done on a regular, long-term basis – can reduce your risk of cardiovascular disease.

Stress

Stress refers to the state of psychological tension caused by physical, emotional, socio-economic, or mental pressure. It is a normal human response which serves as a built-in warning mechanism to restrain us from pushing ourselves beyond our subjective limits.

While moderate amounts of stress may sometimes be good in that it makes you exert yourself harder and thus improves your performance, excessive stress – i.e. stress which is disproportionate to the pressuring circumstances encountered or which interferes with normal daily life – can be harmful to your health. In particular, people who are under stress may develop habits such as smoking or overeating, which are in themselves risk factors for cardiovascular disease.

In addition, researchers increasingly believe that stress may itself be a contributory factor for heart disease. For instance, some studies have found a significant correlation between work stress and the incidence of coronary heart disease; others have revealed a significantly higher level of stress among victims of cardiac death in the final months of their lives compared with people who die of other causes.

It is thus vital that you manage and control the amount of stress in your life well.

Factors you cannot change

While we are unable to reduce the risk of cardiovascular disease arising from this category of factors, it is important for us to be informed about these risk factors and ascertain whether we are at high risk of developing heart disease. If we do belong to this category, we should then take steps to modify the risk factors which we can change.

Age

A person’s risk of developing cardiovascular disease increases with age.

On average, 80% of those who die of coronary heart disease are aged 65 and above.

Gender

Men

Men generally face a much higher risk of heart disease than women. They also tend to suffer heart attacks earlier in life. After women reach menopause however, they are just as likely to have heart attacks as their male counterparts of equal age; they are also more likely to die from such cardiac complications than the latter.

Women At Risk

Heart disease is often regarded as a “male” disease. Statistics, however, belie this perception.

Cardiovascular disease is the largest single cause of female mortality and accounts for one-third of all deaths among women worldwide, killing more than eight million women annually. A similar trend can be seen in Singapore, where cardiovascular disease is likewise the leading cause of death for women. Three categories of women – namely, menopausal women, women taking oral contraceptives, and pregnant women – are particularly vulnerable in this respect.

Women who have reached menopause have a markedly higher risk of coronary heart disease and heart attack than their pre-menopausal counterparts. This is because of the drop in the female sex hormone oestrogen following menopause. Oestrogen is thought to have a protective effect on women’s hearts by causing women to have, relative to men, a lower systolic blood pressure, a lower level of LDL (bad) cholesterol, and a higher level of HDL (good) cholesterol. Consequently, less cholesterol deposits build up in the arteries of women, thereby reducing their risk of developing cardiovascular disease.

As a woman nears the age of menopause however, her ovaries produce less and less oestrogen. This leads to a corresponding increase in her “bad” cholesterol level and blood pressure, coupled with a decrease in her “good” cholesterol level. In the years following menopause, a woman’s blood lipid levels and risk of heart disease rise significantly and become similar to those of a man.

Until recently, it was thought that hormone replacement therapy (HRT) consisting of either oestrogen alone or oestrogen combined with progestin would protect post-menopausal women against heart disease in the same way as natural oestrogen does before the onset of menopause.

Studies conducted by the United States’ Women’s Health Initiative in 2002 and 2003 have, however, cast doubt on this belief. These studies suggest that HRT in the form of oestrogen alone has no impact either way on heart disease in menopausal women. More alarmingly, the research indicates that taking oestrogen alone appears to increase the risk of stroke and uterine cancer, while combination HRT consisting of oestrogen plus progestin may lead to an increased risk of breast cancer. In light of these findings, post-menopausal women who already have heart disease should avoid HRT altogether and should instead try to protect their hearts by addressing modifiable risk factors such as hypertension, high levels of “bad” cholesterol, smoking, and lack of exercise.

Another group of women who face a slightly higher than average risk of cardiovascular disease is those who take oral contraceptives. These women may find their blood lipid levels detrimentally affected by the hormones contained in these pills. They are also more likely to have blood clots forming in vital blood vessels. If a woman taking oral contraceptives is also a smoker, her risk of developing cardiac complications would all the more rise, especially once she reaches the age of 35.

As for pregnant women, they face a greater likelihood of developing palpitations, hypertension, and congestive heart failure because the metabolic work of the heart increases by about 30-50% in the course of pregnancy. Pregnancy-related palpitations are rarely dangerous. Hypertension and congestive heart failure, in contrast, are potentially more serious and require close monitoring. As such, women with existing heart problems should consult their cardiologists before they become pregnant so that their conditions can be evaluated and stabilised before the changes of pregnancy occur.

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Family History

A family history of stroke or heart disease, especially if it occurred at an early age for the affected family member, is a strong risk factor for cardiovascular illnesses. This is because some of the other contributory factors in this context such as diabetes, high blood pressure, and high LDL (bad) cholesterol may be inherited by children from their parents. In addition, people often behave and act as their parents and siblings do. As a result, the genes and habits that cause us to be sedentary, to smoke, to be overweight / obese, or to follow poor diets often tend to cluster in families.

Familial Hypercholesterolemia (FH)

What is Familial Hypercholesterolemia (FH)?

FH is a genetic condition in which high cholesterol levels are passed down in families, increasing the risk of premature heart disease (i.e. chest pain, heart attacks, strokes) by up to 20 times over people without the condition.

It is the most common form of inherited heart disease, with one baby born with FH every minute1. Worldwide, 1 in 250 people have FH1. This means that approximately 20,000 people are affected in Singapore.

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