Cardiovascular disease develops gradually, usually over decades, as cholesterol-rich particles accumulate inside artery walls and trigger a cycle of inflammation, scarring, and narrowing that eventually restricts blood flow or causes a sudden clot. An estimated 19.8 million people died from cardiovascular disease in 2022, roughly 32% of all deaths worldwide. The process starts far earlier than most people realize, often in adolescence, and accelerates based on a handful of modifiable risk factors.
It Starts With Damage to the Artery Lining
Your arteries are lined with a single layer of cells called the endothelium. This lining does more than just hold blood in. It actively controls how wide or narrow the artery stays, prevents blood from clotting where it shouldn’t, and keeps cholesterol from seeping into the artery wall. When this lining is healthy, it produces nitric oxide, a molecule that relaxes blood vessels, blocks clot formation, and protects cholesterol particles from becoming chemically altered.
The same risk factors you’ve heard about for years are the ones that damage this lining: high cholesterol, high blood pressure, smoking, diabetes, and genetic predisposition. These stressors make the endothelium leaky and less able to produce nitric oxide. Once that protective barrier weakens, cholesterol-carrying particles (particularly LDL, the “bad” cholesterol) begin slipping through the artery wall and lodging in the tissue underneath. High LDL levels make this worse in a direct, measurable way: excess LDL reduces the endothelium’s nitric oxide output, which in turn makes it easier for even more LDL to enter and become chemically oxidized. That oxidized LDL is where the real trouble begins.
How Cholesterol Turns Into Plaque
Once LDL particles penetrate the artery wall, they bind to structural proteins in the tissue and undergo chemical changes, including oxidation. These modified particles act like an alarm signal. The endothelium responds by producing molecules that attract immune cells, particularly a type of white blood cell called monocytes, from the bloodstream.
Monocytes squeeze through the endothelium into the artery wall, where they mature into macrophages, the immune system’s cleanup crew. These macrophages engulf the oxidized LDL through specialized receptors on their surface. The problem is that unlike the body’s normal cholesterol-processing pathways, these receptors don’t have an off switch. The macrophages keep consuming oxidized LDL until they’re bloated with fat droplets, transforming into what pathologists call “foam cells.” This process happens even at very early stages of disease. Clusters of dead and dying foam cells create the first visible sign of atherosclerosis: a fatty streak, a yellowish patch inside the artery wall.
Fatty streaks can appear in adolescence. Pooled data from multiple studies suggest that cardiovascular health scores begin declining around age 17, which aligns with the early formation of these streaks in arterial tissue.
From Fatty Streak to Dangerous Plaque
A fatty streak by itself doesn’t block blood flow or cause symptoms. The danger comes from what happens next, often over years or decades. Dead foam cells and other debris continue to accumulate, forming a growing core of cholesterol, cellular waste, and inflammatory molecules inside the artery wall. Smooth muscle cells migrate over this mess and build a fibrous cap on top, essentially walling it off from the bloodstream.
This combination of a cholesterol-rich core beneath a fibrous cap is an atherosclerotic plaque. As it grows, it narrows the artery’s internal opening, leaving less room for blood to pass through. A plaque that blocks 70% or more of an artery’s diameter can start causing symptoms during exertion, like chest pain (angina) during exercise or leg cramps when walking. But many plaques cause no symptoms at all until something more sudden happens.
Inflammation inside the plaque is what determines whether it stays stable or becomes dangerous. Inflammatory activity weakens the fibrous cap, making it thinner and more fragile. C-reactive protein, a marker of inflammation that can be measured with a blood test, correlates with how vulnerable plaques are to breaking apart. People with higher levels face a greater risk of heart attack and stroke, in part because their plaques are more likely to be progressing and destabilizing.
How a Plaque Causes a Heart Attack or Stroke
Most heart attacks don’t happen because a plaque slowly grows until it completely blocks an artery. They happen because a plaque suddenly breaks open or erodes, triggering a blood clot that blocks blood flow within minutes. There are two distinct ways this occurs.
Plaque rupture is the more common mechanism. It happens when the fibrous cap over a plaque becomes thin and tears open, exposing the cholesterol-rich core underneath to the bloodstream. The body treats this like a wound and forms a large clot dominated by red blood cells and a protein called fibrin. These plaques tend to have large pools of accumulated fat and lots of inflammatory cells eating away at the cap from the inside.
Plaque erosion works differently. The fibrous cap stays intact, but the endothelial cells covering the plaque’s surface are lost, often at points where blood flow is turbulent, like where arteries branch. The exposed surface attracts platelets, forming a clot that is smaller and made mostly of platelets rather than red blood cells. Erosion-prone plaques tend to be rich in smooth muscle cells with smaller or even invisible fat cores, making them harder to detect on imaging.
In either case, the resulting clot can partially or completely block the artery. If this happens in a coronary artery feeding the heart muscle, the result is a heart attack. In an artery supplying the brain, it causes a stroke.
What Speeds Up the Process
Several well-established risk factors accelerate every stage of this progression, from the initial endothelial damage through plaque growth and rupture.
- High blood pressure physically stresses artery walls. Under current U.S. guidelines, hypertension begins at a blood pressure of 130/80 mm Hg, with readings at or above 140/90 classified as stage 2 and requiring both lifestyle changes and medication in most cases.
- High LDL cholesterol directly fuels plaque formation by increasing the amount of LDL entering artery walls and reducing nitric oxide protection.
- Smoking damages the endothelium and promotes oxidation of LDL, accelerating both the initiation and progression of plaques.
- Diabetes causes endothelial dysfunction through chronically elevated blood sugar, and people with diabetes tend to develop more widespread and faster-progressing atherosclerosis.
- Chronic kidney disease adds a layer of risk that goes beyond traditional factors. Abnormal calcium and phosphate metabolism, chronic inflammation, and oxidative stress promote arterial calcification and stiffening, which is why people with kidney disease have dramatically higher rates of cardiovascular death.
Lipoprotein(a): A Genetic Wild Card
Lipoprotein(a), often written as Lp(a), is a cholesterol-carrying particle similar to LDL but with an added protein that makes it stickier and more inflammatory. Your Lp(a) level is almost entirely determined by genetics, and roughly one in five people has levels high enough to meaningfully increase cardiovascular risk. Unlike regular LDL, Lp(a) promotes clotting and increases inflammation in ways that make existing plaques more likely to rupture. High levels are also linked to narrowing of the aortic heart valve. Standard cholesterol tests don’t measure Lp(a), so most people with elevated levels don’t know it unless they specifically request the test.
The Timeline Most People Don’t Expect
Atherosclerosis is not a disease of old age that appears suddenly. Fatty streaks, the earliest stage, have been documented in teenagers. The process typically unfolds over 20 to 40 years before producing symptoms or events. Someone who develops high blood pressure or starts smoking in their twenties may be silently building plaque for decades before experiencing chest pain or a heart attack in their fifties or sixties.
This long, silent timeline is precisely what makes cardiovascular disease so deadly. By the time symptoms appear, the disease is usually advanced. At least 38% of premature deaths from noncommunicable diseases in people under 70 are caused by cardiovascular disease. The factors that drive it, including cholesterol levels, blood pressure, blood sugar, smoking, and body weight, are all measurable and modifiable well before plaque reaches a dangerous stage.