American Heart Association scientific position
Extensive clinical and statistical studies have identified several factors that increase the risk of coronary heart disease and heart attack. Major risk factors are those that medical research has shown significantly increase the risk of heart and blood vessel (cardiovascular) disease. Contributing risk factors are associated with increased risk of cardiovascular disease, but their significance and prevalence haven’t yet been precisely determined.
The American Heart Association has identified several risk factors for coronary heart disease. Some of them can be modified, treated or controlled, and some can’t. The more risk factors a person has, the greater the chance that he or she will develop heart disease. Also, the greater the level of each risk factor, the greater the risk. For example, a person with a total cholesterol of 300 mg/dL has a greater risk than someone with a total cholesterol of 240 mg/dL, even though all people with a total cholesterol of 240 or higher are considered high risk.
What are the major uncontrollable risk factors for coronary heart disease?
Increasing age — About 82% of people who die of coronary heart disease are 65 or older.
Male sex (gender) — The lifetime risk of developing CHD after age 40 is 49% for men and 32% for women. The incidence of CHD in women lags behind men by 10 years for total CHD and by 20 years for more serious clinical events such as MI and sudden death.
Heredity (including Race) — Children of parents with heart disease are more likely to develop it themselves. African Americans have more severe high blood pressure than Caucasians and a higher risk of heart disease. Heart disease is also higher among Mexican Americans, American Indians, native Hawaiians and some Asian Americans. This is partly due to higher rates of obesity and diabetes. Most people with a strong family history of heart disease have one or more other risk factors. Just as you can't control your age, sex and race, you can't control your family history. Therefore, it's even more important to treat and control any other risk factors you have.
Other major risk factors that can be lowered by modification, treatment or control.
Tobacco smoke — Smokers’ risk of developing CHD is two to four times that of nonsmokers'. Smokers who have a heart attack are more likely to die and die suddenly (within an hour) than nonsmokers. Cigarette smoking also acts with other risk factors to greatly increase the risk for coronary heart disease. People who smoke cigars or pipes seem to have a higher risk of death from coronary heart disease (and possibly stroke), but their risk isn't as great as cigarette smokers'. Constant exposure to other people's smoke — called environmental tobacco smoke, secondhand smoke or passive smoking — increases the risk of heart disease even for nonsmokers.
High blood cholesterol levels — The risk of coronary heart disease rises as blood cholesterol levels increase. When other risk factors (such as high blood pressure and tobacco smoke) are present, this risk increases even more. A person's cholesterol level is also affected by age, sex, heredity and diet.
High blood pressure — High blood pressure increases the heart’s workload, causing the heart to enlarge and weaken over time. It also increases the risk of stroke, heart attack, kidney failure and heart failure. When high blood pressure exists with obesity, smoking, high blood cholesterol levels or diabetes, the risk of heart attack or stroke increases several times.
Physical inactivity — An inactive lifestyle is a risk factor for coronary heart disease. Regular, moderate-to-vigorous physical activity is important in preventing heart and blood vessel disease. Even moderate-intensity physical activities are beneficial if done regularly and long-term. More vigorous activities are associated with more benefits. Physical activity can help control blood cholesterol, diabetes and obesity, as well as help lower blood pressure.
Obesity and overweight — People who have excess body fat — especially if a lot of it is in the waist area — are more likely to develop heart disease and stroke even if they have no other risk factors. Excess weight increases the strain on the heart, raises blood pressure and blood cholesterol and triglyceride levels, and lowers HDL (good) cholesterol levels. It can also make diabetes more likely to develop. Many obese and overweight people have difficulty losing weight. If you can lose as little as 10 to 20 pounds, you can help lower your heart disease risk.
Diabetes mellitus — Diabetes seriously increases the risk of developing cardiovascular disease. Even when glucose levels are under control, diabetes greatly increases the risk of heart disease and stroke. From two-thirds to three-quarters of people with diabetes die of some form of heart or blood vessel disease. If you have diabetes, it's important to work with your healthcare provider to manage your diabetes and control any other risk factors you can.
What other factors contribute to heart disease risk?
Stress — Individual response to stress may be a contributing factor. Some scientists have noted a relationship between coronary heart disease risk and stress in a person’s life, their health behaviors and socioeconomic status. These factors may affect established risk factors. For example, people under stress may overeat, start smoking or smoke more than they otherwise would.
Sex hormones — These seem to play a role in heart disease. It’s well known that men have more heart attacks than women do before the age of menopause. Several population studies show that the loss of natural estrogen as women age may contribute to a higher risk of heart disease after menopause. If menopause is caused by surgery to remove the uterus and ovaries, the risk of heart attack rises sharply. If menopause occurs naturally, the risk rises more slowly. Hormones also affect blood cholesterol. Female hormones tend to raise HDL ("good") cholesterol and lower total blood cholesterol. Male hormones do the opposite.
Birth control pills — The early forms, with higher doses of estrogen and progestin, increased a woman’s risk of heart disease and stroke, especially in older women who smoked heavily. Newer, lower-dose oral contraceptives carry a much lower risk of cardiovascular disease, except for women who smoke or have high blood pressure. If a woman taking oral contraceptives has other risk factors (and especially if she smokes), her risk of developing blood clots and having a heart attack goes up. It rises even more after age 35. Women with a history of heart disease don't benefit in reducing further heart attacks by taking hormone replacement therapy (HRT).
Excessive alcohol intake — Drinking too much alcohol can raise blood pressure, cause heart failure and lead to stroke. It can contribute to high triglycerides, cancer and other diseases, and produce irregular heartbeats. It also contributes to obesity, alcoholism, suicide and accidents. The risk of heart disease in people who drink moderate amounts of alcohol (an average of one drink for women or two drinks for men per day) is lower than in nondrinkers. One drink is defined as 1–1/2 fluid ounces (fl oz) of 80-proof spirits (such as bourbon, Scotch, vodka, gin, etc.), 1 fl oz of 100-proof spirits, 4 fl oz of wine, or 12 fl oz of beer. It’snot recommended that nondrinkers start using alcohol or that drinkers increase their intake.
Stroke risk factors
The American Heart Association has identified several factors that increase the risk of stroke. The more risk factors a person has, the greater the chance that he or she will have a stroke. Some of these you can’t control, such as increasing age, family health history, race and gender. But you can modify, treat or control most risk factors to lower your risk of stroke. Factors resulting from lifestyle or environment can be modified with a healthcare provider's help.
What are the risk factors for stroke?
Increasing age — The chance of having a stroke about doubles for each decade of life after age 55. While stroke is common among the elderly, over 25 percent of people who have strokes are under age 65.
Sex (gender) — Stroke is more common in men than in women. In most age groups, more men than women will have a stroke in a given year. At older ages, the incidence is higher in women than in men. Overall, more women than men die of stroke.
Heredity (family history) and race — The chance of stroke is greater in people who have a family history of stroke. African Americans have a much higher risk of disability and death from a stroke than whites, in part because blacks have high blood pressure and diabetes more often. Asian/Pacific Islanders and Hispanics also have a high risk of stroke.
Prior stroke — The risk of stroke for someone who has already had one is many times that of a person who has not.
High blood pressure — High blood pressure is defined in an adult as a systolic pressure of 140 mm Hg or higher and/or a diastolic pressure of 90 mm Hg or higher or taking antihypertensive medicine; or having been told at least twice by a physician or other health professional that one has HBP. It's a major risk factor for stroke. Many people believe the effective treatment of high blood pressure is a key reason for the accelerated decline in the death rates for stroke.
Cigarette smoking — Cigarette smoking is an important risk factor for stroke. The nicotine and carbon monoxide in cigarette smoke damage the cardiovascular system in many ways. Using birth control pills and smoking cigarettes greatly increases stroke risk.
Diabetes mellitus — Diabetes is an independent risk factor for stroke and is strongly correlated with high blood pressure. While diabetes is treatable, having it still increases a person’s risk of stroke. People with diabetes often also have high cholesterol and are overweight, increasing their risk even more.
Heart disease — A diseased heart increases the risk of stroke. The percentage of people with a first myocardial infarction who will have a stroke within five years at ages 40–69 is 4 percent of men and 12 percent of women. At age 70 and older, 6 percent of men and 11 percent of women will have a stroke after having a heart attack. Atrial fibrillation (the rapid, uncoordinated quivering of the heart’s upper chambers), in particular, raises the risk for stroke. Heart attack is also the major cause of death among stroke survivors.
Transient ischemic attacks (TIAs) — TIAs are "mini strokes" that produce stroke-like symptoms but no lasting damage. They're strong predictors of stroke. Approximately 15% of all strokes are heralded by a TIA.
High red blood cell count — A moderate or marked increase in the red blood cell count is a risk factor for stroke. The reason is that more red blood cells thicken the blood and make clots more likely.
Sickle cell anemia — This genetic disorder mainly affects African-American and Hispanic children. "Sickled" red blood cells are less able to carry oxygen to the body’s tissues and organs. These cells also tend to stick to blood vessel walls, which can block arteries to the brain and cause a stroke.
What other factors can affect the risk of stroke?
Socioeconomic factors — There’s some evidence that people of lower income and educational levels have a higher risk for stroke.
Excessive alcohol intake — Excessive drinking (an average of more than one drink per day for women and more than two drinks per day for men) and binge drinking can lead to stroke. It can also raise blood pressure, contribute to obesity, high triglycerides, cancer and other diseases, and cause heart failure.
Certain kinds of drug abuse — Intravenous drug abuse carries a high risk of stroke from a cerebral embolism (blood clot in the brain). Cocaine use has been closely related to strokes, heart attacks and a variety of other cardiovascular complications. Some of them have been fatal even in first-time cocaine users.
How are heart disease risk factors related to stroke?
Some risk factors affect the risk of stroke indirectly by increasing the risk of heart disease. These secondary risk factors include:
- High blood cholesterol and triglycerides
- Physical inactivity
- Obesity or overweight