Atherosclerosis is a buildup of plaque inside your arteries that narrows the space blood flows through

Atherosclerosis starts when cholesterol, fat, and other substances accumulate on the inner wall of an artery. Over time, this buildup—called plaque—hardens and thickens, making the artery narrower and stiffer. The result is that less blood can flow through, and the oxygen-rich blood your organs and tissues need has a harder time reaching them. This process usually takes years or decades, which is why atherosclerosis is sometimes called a "silent" disease: you may not notice anything wrong until the narrowing becomes severe.

The plaque itself is made of cholesterol, calcium, fibrous tissue, and cells called macrophages. As plaque builds up, it can rupture—crack open—and trigger a blood clot to form right there in the artery. If that clot blocks blood flow completely, you can have a heart attack or stroke, depending on which artery is affected. This is why atherosclerosis is dangerous even when you feel fine.

Key Takeaways

  • Atherosclerosis develops when cholesterol and fat accumulate inside artery walls, forming plaque that narrows the space blood travels through.
  • The process usually takes years or decades and often causes no symptoms until the blockage becomes severe enough to restrict blood flow.
  • Plaque can rupture and trigger a blood clot, which may completely block an artery and cause a heart attack or stroke.
  • High cholesterol, high blood pressure, smoking, diabetes, and family history all increase the risk of atherosclerosis developing.
  • Lifestyle changes and medications can slow atherosclerosis or prevent it from worsening, even after plaque has begun to form.

How plaque starts to form inside artery walls

Atherosclerosis begins with damage to the inner lining of an artery, called the endothelium. This damage can come from high blood pressure, high cholesterol, smoking, or inflammation in the body. Once the endothelium is damaged, cholesterol particles—especially low-density lipoprotein (LDL), often called "bad cholesterol"—slip through and get trapped in the artery wall.

Your immune system responds to these trapped cholesterol particles by sending white blood cells called macrophages to the area. The macrophages try to clean up the cholesterol but end up becoming filled with it, turning into cells called foam cells. These foam cells accumulate and form the beginning of plaque. Smooth muscle cells in the artery wall also migrate to the area and multiply, adding to the growing plaque deposit. This whole process can start in childhood or young adulthood, especially if risk factors are present.

Why some people develop atherosclerosis faster than others

Your genes play a significant role in how quickly atherosclerosis develops. If your parents or close relatives had heart attacks or strokes at a young age, your risk is higher. But genes are not destiny—lifestyle factors often matter more. High LDL cholesterol, high blood pressure, smoking, diabetes, obesity, and physical inactivity all speed up plaque formation. Chronic inflammation in the body, which can result from conditions like rheumatoid arthritis or from smoking, also accelerates atherosclerosis.

Age and sex affect risk too. Men typically develop atherosclerosis earlier than women, though women's risk rises significantly after menopause. The longer you live with risk factors, the more time plaque has to accumulate. Someone who smokes, has high cholesterol, and is sedentary may develop significant atherosclerosis by their 40s, while someone with the same genetic risk but healthy habits may not show signs until their 60s or 70s.

What happens as plaque narrows the artery

As plaque thickens, it takes up more and more space inside the artery. When the artery is narrowed by about 70 percent or more, blood flow becomes restricted enough that you may start to feel symptoms. In the heart, this often means chest pain or pressure—called angina—especially during exercise or stress, when your heart needs more oxygen. In the legs, narrowed arteries can cause cramping or pain when you walk. In the brain, narrowed arteries may cause no symptoms until a clot forms and blocks blood flow completely.

The body sometimes adapts to gradual narrowing by developing small new blood vessels that bypass the blocked artery, a process called collateral circulation. This can help reduce symptoms, but it is not a complete solution and does not stop the underlying atherosclerosis from progressing.

The difference between stable and unstable plaque

Stable plaque is thick and calcified—it has hardened over time. It narrows the artery but is less likely to rupture suddenly. Unstable plaque has a thin, fibrous cap covering a soft, lipid-rich core. This type is more prone to cracking open, which can happen without warning. When unstable plaque ruptures, the body treats it like an injury and sends platelets and clotting factors to seal the breach. This can form a blood clot that either partially or completely blocks the artery.

A plaque rupture is what usually causes a heart attack or stroke, rather than the gradual narrowing itself. This is why someone can feel fine one day and have a heart attack the next—the plaque was already there, but the rupture and clot formation happened suddenly. Doctors cannot always predict which plaques will rupture, which is why managing risk factors and taking medications like statins and aspirin is important even when you have no symptoms.

How atherosclerosis affects different parts of the body

Atherosclerosis can develop in arteries throughout your body, and the symptoms depend on which arteries are affected. In the coronary arteries that supply the heart, it causes chest pain, shortness of breath, or heart attack. In the carotid arteries in the neck that supply the brain, it increases stroke risk. In the peripheral arteries in the legs and arms, it causes pain with walking or numbness in the extremities. In the renal arteries that supply the kidneys, it can lead to kidney damage and high blood pressure.

Many people have atherosclerosis in multiple locations at once. If you have plaque in your coronary arteries, there is a good chance you also have it in your carotid or peripheral arteries. This is why doctors often screen for atherosclerosis in multiple locations if they find it in one place.

What slows or stops atherosclerosis from getting worse

Atherosclerosis cannot be reversed once plaque has formed, but its progression can be slowed or halted. Lowering LDL cholesterol through statins or other medications reduces the rate at which new plaque forms and can even shrink existing plaque slightly. Controlling blood pressure, quitting smoking, managing diabetes, losing weight, and exercising regularly all reduce the forces that damage artery walls and promote plaque growth.

Medications like aspirin, beta-blockers, and ACE inhibitors also help by reducing the workload on your heart and making blood clots less likely. The earlier you start managing these risk factors, the more you can slow atherosclerosis. Even if you already have significant plaque, making these changes can prevent it from worsening and reduce your risk of a heart attack or stroke.

Frequently Asked Questions

Can you feel atherosclerosis developing?

No, atherosclerosis usually causes no symptoms while it is developing. Most people do not notice anything until the narrowing is severe enough to restrict blood flow during activity, or until a plaque rupture causes a heart attack or stroke. This is why regular screening is important if you have risk factors.

Is atherosclerosis the same as high cholesterol?

No, but high cholesterol is a major cause of atherosclerosis. You can have high cholesterol without atherosclerosis if you have only recently developed elevated levels, and you can have atherosclerosis with normal cholesterol if other factors like smoking or inflammation are driving plaque formation. However, high LDL cholesterol over many years significantly increases your risk.

Can young people get atherosclerosis?

Yes, atherosclerosis can begin in childhood or young adulthood, especially in people with family history, high cholesterol, diabetes, or who smoke. Autopsies of young soldiers have shown plaque in their arteries. This is why managing risk factors early—even in your 20s and 30s—matters for long-term heart health.

What is the difference between atherosclerosis and arteriosclerosis?

Arteriosclerosis is a general term for stiffening of arteries from any cause, including aging. Atherosclerosis is a specific type of arteriosclerosis caused by plaque buildup. All atherosclerosis involves arteriosclerosis, but not all arteriosclerosis is atherosclerosis.

Does exercise reverse atherosclerosis?

Exercise cannot reverse existing plaque, but it slows its growth and can reduce your risk of a plaque rupture by improving blood flow, lowering blood pressure, and reducing inflammation. Combined with medication and diet changes, regular exercise is one of the most effective ways to manage atherosclerosis.