Peripheral arterial disease

Causes of peripheral arterial disease

Peripheral arterial disease (PAD) is usually caused by a build-up of fatty deposits on the walls of the arteries inside the legs. The fatty deposits, called atheroma, are made up of cholesterol and other waste substances.

The build-up of atheroma on the walls of the arteries makes the arteries narrower and restricts the flow of blood to the legs. This process is called atherosclerosis.

People with PAD can experience painful aching in their leg muscles during physical activity because the muscles are not receiving the blood supply they need.

Like all tissue in your body, muscles in your legs need a constant supply of blood to function properly. When you are using your leg muscles, the demand for blood increases four-fold. However, if the arteries in your legs are blocked, the supply of available blood cannot meet the demand.

This shortfall between supply and demand causes your muscles to experience painful aches which usually get better when you rest your legs.

Increased risk of PAD

There are some things that cannot be changed which may increase your chances of developing PAD, such as a family history of heart disease and atherosclerosis, or your age.

As you get older, your arteries naturally begin to harden and get narrower, which can lead to atherosclerosis and then PAD.

However, there are many things that can dangerously speed up this process. These are described below.

Smoking

Smoking is the single most important thing that increases your risk of PAD. Smoking can damage the walls of your arteries. Tiny blood cells, known as platelets, will then form at the site of the damage to try to repair it. This can cause your arteries to narrow.

It is estimated that smokers are six times more likely to develop PAD than non-smokers and more than 80% of people who develop PAD are current or former smokers.

Diabetes

If you have poorly controlled type 1 or type 2 diabetes, the excess glucose in your blood can damage your arteries.

People with diabetes are two to four times more likely to develop PAD, and having a combination of poorly controlled diabetes and PAD is a major risk factor for amputation. People with diabetes and PAD are 15 times more likely to need an amputation than people with PAD who do not have diabetes.

High cholesterol

Cholesterol is a type of fat essential for the body to function.

There are two main types of cholesterol:

  • Low-density lipoprotein (LDL) is the main cholesterol transporter and carries cholesterol from your liver to cells that need it. If there is too much cholesterol for the cells to use, this can cause a harmful build-up in your blood and lead to atherosclerosis. For this reason, LDL cholesterol is known as "bad cholesterol", and lower levels are better.
  • High-density lipoprotein (HDL) carries cholesterol away from the cells and back to the liver, where it is either broken down or passed from the body as a waste product. For this reason, it is referred to as "good cholesterol", and higher levels are better.

Most of the cholesterol your body needs is made by your liver. However, if you eat foods high in saturated fat, the fat is broken down into LDL ("bad cholesterol").

Read more about high cholesterol.

High blood pressure

Your arteries are designed to pump blood at a certain pressure, and if blood pressure is too high (known as hypertension), the walls of the arteries can become damaged. High blood pressure can be caused by:

  • being overweight
  • drinking excessive amounts of alcohol
  • stress
  • smoking
  • a lack of exercise

Homocysteine

Homocysteine is a type of amino acid (the molecules that make up protein) found in the blood. Research has found 30–40% of people with PAD have higher-than-average levels of homocysteine in their blood, and one-in-four people who develop leg pain have extremely high levels.

It has been suggested that high levels of homocysteine may damage the walls of the arteries, leading to atherosclerosis, but this has not been proven.

Vitamin B supplements and eating foods high in folic acid, such as green leafy vegetables or wholegrains, are known to lower homocysteine levels. However, researchers found no significant reduction in risk of cardiovascular disease when people with PAD increased the amount of vitamin B and folic acid in their diet.



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