Causes and Risk Factors of Coronary Artery Disease

There are many factors that contribute to or cause coronary artery disease (CAD). While genetic predisposition does play a role, recent research indicates that lifestyle and environmental factors play an even greater role.

Atherosclerosis, the main cause of CAD, can make the coronary blood vessels (those that supply the heart muscle) stiffen and more prone to forming blood clots. High levels of LDL cholesterol, often referred to as "bad" cholesterol, increase the risk of CAD. 

Common Causes

CAD develops as a slow process in which the arteries that supply blood to the heart muscle become narrow, stiff, and diseased on the inside.

There are several known causes of CAD.

• Atherosclerosis: A disease of the arteries throughout the body, atherosclerosis develops over time. Atherosclerosis causes the smooth, elastic lining of the arteries to become hardened, stiffened, and swollen. It is characterized by a build-up of plaque inside the arteries. Atherosclerosis is the leading cause of CAD. 
• Hypertension: Chronically high blood pressure can contribute to or cause CAD. Over time, excessive pressure on the arteries may interfere with the normal structure of the arteries, as well as their ability to dilate (widen) and constrict (narrow) as they should. 
• High cholesterol: Elevated cholesterol has long been known to contribute to CAD. Excess cholesterol and fat in the blood can damage the inner lining of the arteries. There has been controversy over whether having a high blood cholesterol level is caused by diet, genetics, or inherent metabolism. Certainly, for some people, a change in diet can lower cholesterol levels; for others, a change in diet has no impact. High cholesterol levels are likely caused by a combination of factors that are different for everyone.
• Diabetes: Type I and type II diabetes both increase the chances of developing CAD, and there is a higher chance of CAD if your blood sugar is not well controlled. 
• Obesity: If you weigh more than is considered healthy, you are at an increased risk of developing CAD. This may have to do with lipid (fat molecule) metabolism or hypertension that results from obesity, although obesity itself is associated with an elevated risk of CAD, even when blood pressure and cholesterol levels are normal.
• Inflammation: Inflammation causes damage to the inner lining of the blood vessels of the heart. There are a number of causes of inflammation, including stress, a high-fat diet, dietary preservatives, infection, and illnesses, and they are all believed to contribute to CAD. C-reactive protein (CRP) and fibrinogen, two inflammatory proteins that are associated with an increased risk of CAD, can be measured to assess for inflammation, but the implications of the results are not definitive.
• CRP is a protein released into the bloodstream any time there is active inflammation in the body. The fact that elevated CRP levels are associated with an increased risk of heart attack supports the proposed relationship between inflammation and atherosclerosis.
• Fibrinogen is a blood-clotting factor. Most acute myocardial infarctions (heart attacks) are now known to be due to acute thrombosis, the sudden formation of a blood clot at the site of an atherosclerotic plaque. 

Genetics

There appears to be a genetic component to CAD, and people who have a genetic risk of developing the illness may need to take chronic medication to reduce their risk of heart attack and other complications of CAD. Some of the genetic defects associated with CAD cause alterations of cholesterol metabolism or vascular disease; some make a person more prone to inflammation; and some cause CAD without a well-understood mechanism. 

A study from Canada identified 182 genetic variants associated with CAD. The researchers described this as further evidence that CAD is polygenic, which means there are many genes that can cause the disease. In general, genes that are associated with a polygenic disease can be inherited together but may be inherited in a variety of combinations. The genetic abnormalities studied were particularly common in young people, which is defined as younger than age 40 for men and younger than age 45 for women.

Genetic alterations that result in certain identifiable problems have also been discovered. One study, for example, found that the LDLR rs688 TT genotype is associated with increased susceptibility to CAD in patients, and LDLR rs688 can be used as a predisposing genetic marker for CAD, though the researchers said further studies were needed to confirm their findings.

Genetic susceptibility to CAD may be inherited, and some of the genetic mutations may arise even without an identifiable hereditary cause. In other words, a person can develop a mutation even if it did not come from their parents. 

Lifestyle

There are a number of lifestyle factors that increase the risk of developing CAD. These choices and habits surely look familiar, as they are implicated in myriad health concerns. Though changing them may take great effort, it's effort well-placed.

• Smoking: One of the leading causes of atherosclerosis and CAD, smoking exposes your body to a variety of toxins that damage the internal lining of the blood vessels, making them prone to forming atherosclerotic plaques and blood clots. 
• Diet: An unhealthy diet can contribute to CAD due to high cholesterol, high-fat content, and exposure to preservatives that are not beneficial for the body. A healthy diet is rich in fresh fruits and vegetables, as well as the healthy fats found in nuts, legumes, lean meat, and fish. This type of diet contains vitamins, minerals, and antioxidants, which can help reduce unhealthy fats and harmful atherosclerosis-producing substances in the body. 
• Sedentary lifestyle: Exercise produces hormones and chemicals that increase the level of healthy fats in the body that are known to reduce the damage that contributes to atherosclerosis; without exercise, you miss out on this important benefit. In addition, a sedentary lifestyle contributes to obesity, which increases the risk of developing CAD. 
• Stress: Stress produces a number of hormones that can increase burden on the heart, as well as cause damage to the blood vessels. Unlike some of the other lifestyle risk factors, it is unclear how much of a role stress plays in CAD, but experimental models suggest there is a connection.