The basic process: how atherosclerosis starts

Atherosclerosis happens when a waxy substance called plaque builds up inside your arteries over time. The process usually begins with damage to the inner lining of an artery — the thin layer called the endothelium. This damage can come from high blood pressure, smoking, high cholesterol, or diabetes. Once the lining is damaged, your body's repair system kicks in, but the repair process itself can trigger plaque formation.

When the artery lining is damaged, cholesterol and other fatty substances from your blood seep into the artery wall. White blood cells arrive to clean up the damage, but they get trapped and filled with cholesterol, forming a fatty streak. Over months and years, more cholesterol, calcium, and other materials accumulate in the same spot, hardening into plaque. The plaque narrows the artery, making it harder for blood to flow through.

Key Takeaways

  • Plaque forms when cholesterol and other substances build up in damaged artery linings, a process that usually takes years or decades.
  • High blood pressure, smoking, high cholesterol, and diabetes are the main causes of the artery damage that starts atherosclerosis.
  • As plaque grows, it hardens and narrows the artery, reducing blood flow to the heart, brain, or legs depending on which arteries are affected.
  • A blood clot can form on top of plaque and suddenly block an artery completely, causing a heart attack or stroke.

High cholesterol and how it damages arteries

Cholesterol is a waxy substance your body needs to make hormones and cell membranes, but too much in your blood causes problems. Your body carries cholesterol in packages called lipoproteins. LDL cholesterol (low-density lipoprotein) is the type that deposits in artery walls. When LDL levels are high, more cholesterol gets into the artery lining, especially if that lining is already damaged.

The cholesterol that enters the artery wall gets oxidized — chemically changed — which makes it toxic to the cells around it. This triggers inflammation, which brings more immune cells to the area. These cells engulf the oxidized cholesterol and become foam cells, the building blocks of early plaque. HDL cholesterol (high-density lipoprotein) actually removes cholesterol from artery walls and carries it to the liver, so low HDL levels also increase your risk.

High blood pressure and smoking as plaque triggers

High blood pressure damages artery linings by putting constant stress on them. The force of blood pushing against the artery wall, especially when pressure is consistently elevated, causes tiny tears in the endothelium. These tears are exactly where plaque formation begins. Over time, the repeated injury from high blood pressure creates more and more entry points for cholesterol to seep into the artery wall.

Smoking damages arteries in multiple ways. Chemicals in tobacco smoke directly injure the artery lining, reduce the amount of oxygen in your blood, and make your blood stickier and more likely to clot. Smoking also lowers HDL cholesterol and raises LDL cholesterol, making the cholesterol problem worse. Even secondhand smoke exposure increases atherosclerosis risk, though the effect is smaller than active smoking.

Diabetes and inflammation as accelerators

Diabetes speeds up atherosclerosis because high blood sugar damages artery linings and makes LDL cholesterol more likely to stick to artery walls. People with diabetes also tend to have lower HDL cholesterol and higher triglycerides (another type of blood fat), both of which increase plaque formation. The damage happens faster in people with diabetes, which is why they often develop atherosclerosis at younger ages than people without diabetes.

Chronic inflammation throughout your body also drives atherosclerosis. When you have ongoing inflammation from conditions like rheumatoid arthritis, infections, or obesity, your immune system stays activated. This constant state of inflammation damages artery linings and promotes plaque growth. Some research suggests that inflammation may be just as important as cholesterol in determining who develops atherosclerosis.

Age, family history, and other risk factors

Atherosclerosis develops over decades, so age is a major factor. Men typically develop atherosclerosis in their 40s and 50s, while women often develop it later, after menopause. Your genes also matter — if your parents or siblings had heart attacks or strokes at young ages, your risk is higher. This does not mean you will definitely develop atherosclerosis, but it means you start with more risk and need to manage other factors more carefully.

Other factors that contribute include obesity, physical inactivity, chronic stress, and certain infections. Excess weight increases inflammation and blood pressure. A sedentary lifestyle allows cholesterol to accumulate and blood vessels to weaken. Some infections, particularly those that cause chronic inflammation, may also promote plaque formation. Menopause in women reduces estrogen, which had been protecting blood vessels, so atherosclerosis risk rises after menopause.

How plaque becomes dangerous

For years, plaque may narrow an artery without causing symptoms. You might not know it is there. But as plaque grows thicker, it restricts blood flow. If an artery becomes 70 percent blocked or more, you may feel chest pain during exertion because your heart is not getting enough oxygen-rich blood. This pain is called angina.

The real danger comes when plaque ruptures. The plaque has a fibrous cap covering it, but this cap can crack. When it does, the fatty core inside is exposed to blood, triggering an immediate blood clot. This clot can completely block the artery in seconds. If the blocked artery supplies the heart, you have a heart attack. If it supplies the brain, you have a stroke. This is why people can have a heart attack or stroke suddenly, even if they had no warning symptoms before.

Frequently Asked Questions

Can atherosclerosis go away on its own?

Plaque does not disappear, but it can stabilize and stop growing if you control the underlying causes — lowering cholesterol, managing blood pressure, quitting smoking, and treating diabetes. Some research suggests that intensive treatment may shrink plaque slightly, but the main goal is to prevent it from growing and rupturing.

Is atherosclerosis the same as a heart attack?

No. Atherosclerosis is the buildup of plaque in arteries over time. A heart attack happens when a blood clot suddenly blocks an artery that supplies the heart. You can have atherosclerosis for years without having a heart attack, but most heart attacks occur in people with atherosclerosis.

Can you have atherosclerosis without high cholesterol?

Yes. While high cholesterol is a major risk factor, atherosclerosis can develop from high blood pressure, smoking, diabetes, or chronic inflammation alone. Some people with normal cholesterol levels still develop atherosclerosis because of other risk factors.

Does exercise help prevent atherosclerosis?

Yes. Regular physical activity lowers blood pressure, improves cholesterol levels, helps control weight, and reduces inflammation — all of which slow atherosclerosis development. Exercise also improves blood flow and helps your body use oxygen more efficiently.

What age should I start worrying about atherosclerosis?

Plaque can begin forming in childhood, especially in people with family history or risk factors. Most people benefit from managing cholesterol and blood pressure starting in their 20s or 30s, particularly if they have family history of early heart disease or multiple risk factors.