How Are Hypertension, Heart Disease and Stroke Related?

There are two types of stroke. The more common, ischemic, accounts for 87 percent of all strokes. It occurs when a clot obstructs a blood vessel, cutting off blood to the brain. The second type of stroke, called hemorrhagic, occurs when a weakened blood vessel ruptures, causing bleeding in the brain.

The hypertension connection

Despite the prevalence of heart attacks and stroke, the human body often reveals lots of clues that these health issues might be on their way. Hypertension is a good example: Consistently high blood pressure readings suggest your artery walls have become less elastic, which, over time, decreases the flow of blood and oxygen to the heart. The pressure can also cause damage in the artery lining. When the body responds to the injury, a clot can form, blocking the vessel. “When this happens, the red blood cells can’t fit – and get closed off,” explains Andrew Budson, M.D., professor of neurology at Boston University School of Medicine and chief of cognitive and behavioral neurology at VA Boston Healthcare System. When the block prevents blood flow to the brain, “that’s a stroke.”

No wonder then that hypertension “is the most important risk factor for stroke,” says Mitchell Elkind, M.D., professor of neurology and epidemiology at Columbia University and chief clinical science officer for the American Heart Association. He estimates that hypertension contributes to about half of all strokes and the vast majority — about 80 percent — of hemorrhagic strokes.

“When you have years and years of elevated blood pressure pounding on the walls of the blood vessels, it damages the walls,” says Budson.

About 116 million U.S. adults – nearly one in two – have high blood pressure (defined as 130/80 mmHG) or higher. Only about one in four are taking medication or have made lifestyle changes to lower their numbers, according to the CDC.  Many people don’t even know they have high blood pressure because there are no symptoms. That’s one reason it’s called the “silent killer.”

“Addressing and treating hypertension is vitally important to reducing the risk of stroke,” says Beth Abramson, M.D., the Paul Albrechtsen Professor in cardiac prevention and women’s cardiovascular health in the division of cardiology at St. Michael’s Hospital in Toronto. Aging happens, but hypertension we can do something about; it’s a controllable risk factor. “Addressing hypertension, or high blood pressure, will have a tremendous impact on reducing the risk of stroke.”

How high cholesterol boosts stroke risk

High cholesterol — which also can result in plaque buildup (deposits of fat, cholesterol and other substances) — is another danger. Hypertension injures the blood vessel lining, which allows plaque to accumulate in the blood vessels, known as atherosclerosis. As a result, the blood vessels become narrow, making it easier for a clot to get stuck. Sometimes, pieces of plaque can break off, lodging in a narrow blood vessel. If that vessel is in the brain, a stroke can happen; if it blocks flow to the heart, a heart attack can happens.

About one-fourth of U.S. adults, or more than 86 million, have total cholesterol of 200 mg/dL or higher in 2017-2020 according to a 2023 report by the American Heart Association. Optimal levels are about 150 milligrams per deciliter (mg/dL) for total cholesterol; about 100 mg/dL for LDL (“bad” cholesterol); and greater than or equal to 40 mg/dL in men and 50 mg/dL in women for HDL (“good” cholesterol). Triglyceride levels should be less than 150 mg/dL. When hypertension develops, the LDL becomes the main target. It needs to be brought down below 70 mg/dL, with cholesterol-lowering medications or changes in diet.

A-fib also raises stroke risk

An irregular heartbeat or arrhythmia known as atrial fibrillation, or A-fib, is another risk factor for stroke. People with A-fib are five times more likely to suffer a stroke than those who don’t have the disorder, according to the CDC. An estimated 1 in 7 strokes result from A-fib. The risk increases with age and with hypertension.

“When the heart goes into A-fib, the rhythm of the upper chambers changes dramatically from a normal predictable electrical cycle to chaotic rapid, unpredictable waves of electricity that wash back and forth,” Lloyd-Jones says. “Those upper chambers don’t contract in an organized fashion, they just wiggle. It looks like a bag of worms.”

When this happens, blood can stagnate, he says. “Anytime blood is sitting still, it tends to clot,” he says. “When a clot forms and breaks off, the most common place it will go is to the brain.”

Some people have no A-fib symptoms and don’t know they have it. Others may experience irregular heartbeat, heart palpitations, lightheadedness, extreme fatigue, shortness of breath and chest pain. A-fib is treated with medication and sometimes surgery, and can be diagnosed with an EKG, or electrocardiogram, a test that often is part of a routine physical, Elkind says.

The bottom line when it comes to the heart and the brain: They are closely linked.

“Both have arteries that need to stay open in order to get blood and oxygen to their tissues,” Budson says. “The brain and the heart have a relationship. If you want to keep your brain healthy, you have to keep your heart healthy.”