What are the Causes and Risk Factors of CAD?
It's important to know the factors that may increase your risk for CAD. The more risk factors you have, the more likely you are to develop the disease. You can control many risk factors, which may help prevent or delay CAD. Research suggests that CAD starts when certain factors damage the inner layers of the coronary arteries. These factors include:
Smoking: Smoking causes about one in every five deaths in the US each year. It’s the main preventable cause of death and illness in the US. It harms nearly every organ in the body, including the heart, blood vessels, lungs, eyes, mouth, reproductive organs, bones, bladder and digestive organs.
The chemicals in tobacco smoke harm your blood cells. They also can damage the function of your heart and the structure and function of your blood vessels, which can limit how much oxygen reaches the body's tissues.
High levels of certain fats and bad cholesterol in the blood: Cholesterol is a waxy, fat-like substance that’s found in all cells of the body. Your body needs some cholesterol to make hormones, vitamin D and substances that help you digest foods. Your body makes all the cholesterol it needs, but cholesterol also is found in some of the foods you eat.
There two kinds of cholesterol in our body. Having healthy levels of both types of cholesterol is important.
- LDL cholesterol is sometimes called “bad” cholesterol. A high LDL level leads to a buildup of cholesterol in your arteries.
- HDL cholesterol is sometimes called “good” cholesterol. This is because it carries cholesterol from other parts of your body back to your liver, which removes the cholesterol from your body.
High blood pressure (HBP): HBP is a serious condition that can lead to CAD, heart failure, stroke, kidney failure and other health problems. "Blood pressure" is the force of blood pushing against the walls of the arteries as the heart pumps blood. If this pressure rises and stays high over time, it can harm the body in many ways.
Blood pressure is considered high if it stays at or above 140/90 mmHg over time. If you have diabetes or chronic kidney disease, high blood pressure is defined as 130/80 mmHg or higher. The mmHg is millimeters of mercury-the units used to measure blood pressure.
Knowing your blood pressure numbers is important, even when you're feeling fine. If your blood pressure is normal, you can work with your health care team to keep it that way. If your blood pressure is too high, treatment may help prevent damage to your body's organs.
- Insulin resistance and diabetes: Insulin is a hormone that helps move blood sugar into cells where it’s used for energy. Insulin resistance is a condition in which the body produces insulin but does not use it effectively. Insulin resistance may lead to diabetes, which is a group of diseases characterized by high blood glucose (sugar) levels.
- Being overweight or obese: The terms “overweight” and “obese” refer to body weight that is greater than what is considered healthy for a certain height.
- Metabolic syndrome: Metabolic syndrome is the name for a group of risk factors (including high blood pressure, high blood sugar, abnormal cholesterol levels and extra body fat around the waist) that raise your risk for CAD and other health problems, such as diabetes and stroke.
- Lack of physical activity: Being physically inactive can worsen other risk factors for CAD, such as unhealthy cholesterol levels, high blood pressure, diabetes and being overweight or obese.
- Unhealthy diet: Foods that are high in saturated and trans fats, cholesterol, sodium (salt) and sugar can worsen other risk factors for CAD.
- Older age: Genetic or lifestyle factors cause plaque to build up in your arteries as you age. By the time you’re middle-aged or older, enough plaque has built up to cause signs or symptoms of CAD. In men, the risk for CAD increases after age 45. In women, the risk for CAD increases after age 55.
- Family history of early heart disease: Your risk increases if your father or a brother was diagnosed with CAD before 55 years of age or if your mother or a sister was diagnosed with CAD before 65 years of age.
Although age and having a family history of early heart disease are risk factors, having one or both of these factors does not mean that you'll develop CAD. Controlling other risk factors often can lessen these influences and help prevent CAD.
Possible Risk Factors
Researchers continue to study other possible risk factors for CAD. 其中包括：
- High levels of a protein called C-reactive protein (CRP) in the blood: CRP may raise the risk of CAD and heart attack. High levels of CRP are a sign of inflammation (swelling) in the body.
- Inflammation: Damage to the arteries’ inner walls may trigger inflammation, the body’s response to injury or infection, and help plaque grow. Research is under way to find out whether reducing inflammation and lowering CRP levels can also reduce the risk of CAD and heart attack.
- High levels of triglycerides: Triglycerides are a type of fat. High levels in the blood may raise the risk of CAD, especially in women.
Other Risk Factors Related to CAD
Other conditions and factors may also contribute to CAD, including:
- Sleep apnea: Sleep apnea is a common disorder in which one or more pauses in breathing or shallow breaths occur while sleeping. Untreated, sleep apnea can increase the risk of high blood pressure, diabetes and even a heart attack or stroke.
- Stress: Research shows that the most commonly reported "trigger" for a heart attack is an emotionally upsetting event, especially one involving anger.
- Alcohol: Heavy drinking can damage the heart and worsen other CAD risk factors. Men should have no more than two drinks containing alcohol a day. Women should have no more than one drink containing alcohol a day.
- Preeclampsia: This condition occurs during pregnancy. The two main signs of preeclampsia are a rise in blood pressure and excess protein in the urine. Preeclampsia is linked to an increased lifetime risk of heart disease including CAD, heart attack, heart failure and high blood pressure.