Do You Know All the Risk Factors for Heart Disease? (Part I)

By Daniel G. Graetzer, Ph.D.
Faculty Member, School of Health Sciences

Note: For American Heart Month, this article is part 1 of a two-part series on heart health. This article discusses the primary risk factors for heart disease.

According to the Centers for Disease Control and Prevention, heart disease is the single leading cause of death for men, women, and people of most racial and ethnic groups in the United States. A narrowed coronary artery reduces blood supply to the heart (a medical condition known as ischemia), which leads to a critical loss of oxygen supply (hypoxia) and a heart attack (myocardial infarction).

If the blockage is not too severe to cause a heart attack, a patient may experience temporary chest pain (angina pectoris). About 30% of heart attack victims experience this type of initial chest pain.

At rest, the heart’s blood supply becomes deficient only when the obstruction of a coronary artery reaches about 80%. At least 50% to 70% occlusion must be present before heart disease can be detected by medical tests such as an electrocardiogram or an angiogram.

Risk factors for heart disease are categorized as primary or secondary. The primary risk factors are those factors that research has shown without question to play a role in the development of heart disease.

Secondary risk factors are not necessarily of less importance, but they may simply need more research to elevate them to primary risk factor status. Many risk factors – such as family history, gender and age – are uncontrollable. However, other risk factors – like smoking or sedentary living – are controllable if you are willing to modify your habits.

The interaction of several heart disease risk factors magnifies their effect above the sum of them individually. For example, if you only have one major risk factor, the chance of heart disease is doubled, whereas possessing three risk factors increases your risk of a heart attack almost tenfold.

Common sense dictates that if you want to reduce the possibility of heart disease, intervention should start as early as possible. Heart disease prevention is always preferable to rehabilitation after a heart attack.

Primary Risk Factors for Heart Disease

There are five primary risk factors for heart disease. They include cigarette smoking, high blood pressure, high blood cholesterol, an elevated triglyceride level and diabetes.

Cigarette Smoking

The probability of death from heart disease for smokers is about 70% greater than nonsmokers, with the risk being directly related to the quantity of cigarettes you smoke daily. For instance, if you smoke two or more packs of cigarettes per day, you have a twofold to threefold greater risk of heart disease. Furthermore, the increase in death rate from heart disease among women in the U.S. almost parallels their increase in smoking.

Nicotine has various effects on the body. For instance, the nicotine intake from chronic smoking increases heart rate and blood pressure, injures blood vessel walls, and speeds up hardening of the arteries. Nicotine also causes blood platelets to cluster and increases blood thickness.

Also, the carbon monoxide in cigarette smoke interferes with oxygen transport by hemoglobin in the blood. Smoking filtered cigarettes may decrease the risk of lung diseases such as bronchitis, emphysema and cancer, but using filtered cigarettes does not minimize the danger of cardiovascular problems.

But there is good news. When you stop smoking – even after 20 years of puffing – the risk of heart disease returns to that of a nonsmoker in a surprisingly short period of time. Ten years after quitting, lung cancer risk is cut in half, and after 15 years, heart disease risk is very close to that of someone who has never smoked.

High Blood Pressure

Hypertension (high blood pressure) affects about 50% of U.S. adults at some point in their lives. The American Heart Association (AHA) defines hypertension as systolic/diastolic pressures that exceed 140/90 millimeters of mercury (mm Hg). By contrast, hypotension (low blood pressure) is below 90/60 mm Hg, and a blood pressure of about 120/80 mm Hg is normal.

When blood pressure within your body remains higher than is necessary for an extended period, the heart’s workload is greatly increased. As a result, you are more at risk for progressive heart failure or a sudden heart attack.

Unlike a toothache or backache, hypertension can go undetected for years because there are generally no other symptoms. Hypertension is only detectable through a routine diagnosis with a stethoscope and pressure cuff. In fact, nearly half of the people who are diagnosed with hypertension during routine screening are unaware that they have it.

If you have high blood pressure, you can reduce it by losing weight, improving your diet, limiting your salt intake (especially if you’re sodium-sensitive). Other steps include limiting your alcohol consumption and reducing your stress.

Women who take oral contraceptives often experience high blood pressure, especially if they also smoke cigarettes. The danger of high blood pressure is further amplified when women using oral contraceptives are also overweight, have had hypertension during pregnancy, have a family history of hypertension or have a medical condition such as kidney disease.

High Blood Cholesterol

High blood cholesterol (hyperlipidemia) and lipid subfractions (such as HDL-C and LDL-C) that are out of their normal ranges place you at a higher risk for heart disease. The average total serum cholesterol level in American adults is 210-215 milligrams per deciliter (mg/dL), and the AHA defines hyperlipidemia as an excess of 200 mg/dL.

A blood cholesterol level of 230 mg/dL doubles your risk of heart attack, and a value of 300 mg/dL increases the risk fourfold. About 38% of the U.S. population have cholesterol levels above 240 mg/dL, with this group experiencing about 60% of all heart disease events. If you have a blood cholesterol level above 240 mg/dL, it is wise to seek immediate medical attention.

Bad and Good Blood Lipoprotein-Cholesterols

There are two types of lipoprotein-cholesterols in your blood: low-density and high-density. Low-density is commonly considered the “bad” cholesterol, while high-density is the “good” cholesterol.

Low-density lipoprotein-cholesterol (LDL-C) transports cholesterol and triglycerides from the liver and intestines to peripheral tissues, where they may be deposited in arterial walls. High levels of LDL-C may be a consequence of a diet high in cholesterol-rich foods and saturated fat. Another cause is heredity.

LDL receptors have been shown to play a role in heart disease. Dr. Michael Brown and Dr. Joseph Goldstein from the University of Texas Medical School were awarded the 1985 Nobel Prize for showing a link between LDL receptors and heart disease. They discovered tiny complex LDL receptors on many cell membranes that control the entry of cholesterol from LDL-C into the body’s tissues.

Persons who are born with a certain genetic disorder called familial hypercholesterolemia cannot produce the required number of LDL receptors. As a result, their cholesterol cannot enter cells and be metabolized at a normal rate. Their cholesterol accumulates in the bloodstream, adhering to cellular walls, blocking blood flow and increasing their risk of heart problems.

There are three types of LDL-C levels:

Optimal – Below 130 mg/dL
Borderline High – Between 130-159 mg/dL
High – 160 mg/dL

As opposed to the “bad” cholesterol, a high level of “good” cholesterol (HDL-C) is associated with a high level of aerobic fitness and helps to prevent cardiovascular disease. HDL-C prevents cholesterol from being deposited on the arterial walls by transporting excess cholesterol to the liver for breakdown and excretion from the body.

Although questions still exist regarding HDL-C, it appears that a high HDL-C level is a consequence of high levels of physical activity and not smoking. Diet does not appear to affect a high HDL-C level. Also, aerobic or endurance physical activities have been shown to increase HDL-C levels more than anaerobic activities such as sprint conditioning or weight training.

Although trained distance runners show about a 20% to 35% higher level of HDL-C (12 mg/dL to 20 mg/dL), you do not have to exercise at the marathon level to increase your HDL-C level. For instance, if you exercise regularly during your lunch hour or other spare time, you may be able to have a 10% (about 5 mg/dL) higher level of HDL-C.

Smokers tend to have lower HDL-C levels as compared to nonsmokers, but a level of HDL-C can increase to a normal level after you stop smoking. The average HDL-C level in American men is about 45 mg/dL, while the average for women is about 55 mg/dL.

The higher HDL-C levels in women may be one of the reasons premenopausal women are at a lower risk of heart disease than men. An HDL-C level below 35 mg/dL is considered low while a level of 55 mg/dL or above is optimal.

Total Cholesterol/HDL-Cholesterol Ratio

The best indicator of heart disease may be the ratio of total serum cholesterol to HDL-C. A Framingham, Massachusetts heart study followed several thousand people for several decades and correlated their cholesterol subfractions with heart disease events. A low “ratio” is desirable as it indicates a low total cholesterol level and/or a high HDL-C level.

The average “ratio” of American men is about 5.0, while the recommended “ratio” is 3.5 or less. For example, a total cholesterol level of 190 mg/dL divided by an HDL-C level of 50 mg/dL will give you a ratio of 3.8, indicating below average risk of coronary disease.

Total Cholesterol/HDL-C Ratio	Classification
>14.0	Highest risk
7.0 – 14.0	High risk
4.5 – 7.0	Average risk
3.5 – 4.5	Below average risk
<3.5	Lowest risk

Triglycerides

Triglycerides, the major storage form of body fat, are stored in adipose tissue cells. These cells are located throughout the body but primarily in the abdominal, hip and thigh regions. When elevated blood triglycerides are combined with a low HDL-C level, the risk of heart disease greatly increases, especially in women.

Exercise, weight reduction and dietary modification are effective ways to lower your triglyceride levels. For example, reducing your intake of alcohol, sweets and soda pop may help to reduce triglycerides in your blood because alcohol and simple sugars such as the glucose and fructose in junk foods stimulate triglyceride production by the liver. A triglyceride level below 150 mg/dL is considered normal, and 200 mg/dL or above is high.

You can improve your cholesterol levels by decreasing your consumption of cholesterol-rich foods and saturated fats (red meat, fried foods, and egg yolks) and increasing your consumption of complex carbohydrate and fiber (fruits, grains, vegetables, rice, and pasta). The average American diet contains approximately 40% total fat, 15% to 20% of which is saturated fat, and a cholesterol intake of 350 to 450 mg/day.

The AHA recommends that your total fat intake should be less than 30% of your total calories, 6% or less of which should be saturated fat. Your cholesterol intake should not exceed 300 mg/day (about one egg yolk). For most Americans, meeting these guidelines would require a 30% to 50% reduction in cholesterol and saturated fat.

Diabetes Mellitus

Diabetes can also place you at a higher risk for heart disease. Type I (insulin-dependent) diabetes generally occurs in younger persons while Type II (non-insulin dependent) diabetes tends to occur later in life. Type I diabetes is associated with a deficiency in insulin with a resulting high blood glucose level.

Diabetes more than doubles the risk of heart disease in men and more than triples the risk in women. Individuals who are at particular risk of heart disease include:

People with Type I diabetes who are over 30 years of age
People who have had Type I diabetes for more than 15 years of their lives
People who have Type II diabetes and are over 35 years of age

Family History of Heart Disease

In some cases, a family history can place you at greater risk for heart disease. If your parent or sibling has had any form of heart disease prior to age 55, your risk of developing heart problems increases.

A family history of other risk factors (diabetes, hypertension or high cholesterol) also increases your risk of heart disease even if these risk factors are not present in your own body. However, the genetic component to heart disease is extremely difficult to quantify separately from environmental influences. A family typically eats together, is exposed to similar stresses in the home, and shares many common experiences that may either increase or decrease heart disease risk.

Part 2 of this article will discuss the secondary risk factors for heart disease and what you can do to maintain your health.