Heart attacks happen all the time. In fact, the CDC estimates that one occurs every 40 seconds in the United States. That adds up to more than 800,000 every year. But what causes them? Heart attacks result from a complex set of circumstances that we’ll walk you through, below. And keep in mind that most heart attacks can be prevented by living your best life: eating and sleeping well, moving your body, and managing stress.
What Is a Heart Attack Again?
A heart attack occurs when your heart can’t get an adequate supply of oxygen-rich blood. This can happen suddenly or over the course of hours, days, or even weeks, and it can permanently damage your heart muscle. It can sometimes be fatal. For many people, having a heart attack is the first indication that their heart is no longer healthy. In other words, it's one of the scariest of wake-up calls.
What, Exactly, Causes a Heart Attack?
The most common cause of a heart attack is coronary artery disease, or CAD. When you have CAD, a waxy material called plaque builds up on the walls of your heart’s arteries, the blood vessels responsible for delivering blood to your ticker. This process of buildup is called atherosclerosis. The plaque itself is made of cholesterol, calcium, fatty substances, and fibrin, a protein that causes blood clots to form.
No one knows exactly what starts the process of atherosclerosis, but it may be set in motion as a result of damage to the inner lining of your arteries due to:
- High cholesterol
- High blood pressure (HBP)
- Lack of exercise
In fact, plaque buildup can begin to develop as early as childhood in kids who are obese, or who have inherited a genetic propensity for high cholesterol, though it develops at a faster rate as you get older.
Patches of plaque tend to form throughout the heart’s medium and large arteries, but they often begin at the spots where the arteries branch. There are two types of plaque: hard and soft. Soft plaque causes most heart attacks because it’s vulnerable to rupturing or tearing. These ruptures can occur spontaneously, but a sudden increase in stress—emotional or physical—can also trigger a rupture, especially in someone already at high risk of a heart attack. Exercising or having sex can cause them, and so can work stress or anger. They may also occur during times of strife—think war or natural disasters, or even the current stress of the coronavirus pandemic. Stressors like these may boost your heart rate and blood pressure, causing the extremely thin cap on the fatty deposit to break open.
When that occurs, your body’s repair system kicks in and forms a blood clot around the ruptured area. But with your arteries already narrowed, that blood clot may end up causing a complete, or near-complete, blockage in the artery, starving your heart of the blood it requires to function. When this happens, you may (or may not) experience symptoms, but you're definitely having a heart attack.
A few more important details about the causes of heart attacks:
- Though its role is not fully understood, inflammation also plays a significant role in heart disease and your risk of having a heart attack. Inflammation is a normal part of your immune response. When you have an infection or an injury, your body’s repair system tries to fix the problem. Inflammation occurs as part of that process. That’s helpful in the short term, but over time, constant, or chronic, inflammation can cause damage rather than repair it.
In your arteries, inflammation gets triggered by some of the risk factors we’ll discuss below, such as smoking and HBP, which damage the arteries and contribute to plaque buildup. The body may sense this plaque as “foreign,” which again triggers an immune response and leads to further inflammation and damage to your arteries. Over time, this vicious circle primes the plaque to rupture.
- On rare occasions, a heart attack can be triggered by a coronary artery spasm, in which the blood vessels suddenly constrict, cutting off the flow of blood to the heart. This can happen even if you don’t have plaque buildups in your arteries However, if you do have such buildups, a spasm can cause a buildup to rupture, leading to a full-blown heart attack. Experts don’t fully understand what causes such spasms, but they have been linked to smoking cigarettes, doing cocaine and other illicit drugs, heavy drinking, and excessive emotional distress, among other causes.
What Are the Risk Factors for Heart Attack?
A blocked artery may cause a heart attack, but there are many risk factors that increase the likelihood of such a blockage happening in the first place. Many of those we’ll review are modifiable, meaning that you can do something about them, hopefully before you have a heart emergency.
Sometimes, modifying one risk factor will help you reduce others. For example, if you were obese but lost weight, your blood pressure and cholesterol levels likely improved as well. Some risk factors, however, can’t be altered. We’ll take a look at those, too.
First, let’s go over what you can work to change:
If you smoke, do everything in your power to quit. Your heart—and the rest of your body—will thank you. The chemicals and compounds in cigarette smoke, such as nicotine, tar, and carbon monoxide, damage your blood vessels and contribute to the buildup of plaque in your arteries.
- Boosts your blood pressure and heart rate
- Causes chronic inflammation
- Increases your risk of dangerous blood clots—and ups your odds of developing blood clots that can cause heart attacks
- Lowers your HDL, or “good,” cholesterol levels (we’ll get into that in just a moment)
The longer you smoke, the more your risk of heart attack rises. And if you smoke now, your risk of a heart attack is about 2.5 times higher than someone who has never smoked, according to a 2019 study in BMC Medicine. In fact, that same study found that smoking elevates your risk of virtually every type of heart disease. Remember: No amount of smoking is safe. Visit the American Heart Association website for help with smoking cessation. And, while the risks of vaping remain less well understood, e-cigarettes deliver toxic chemicals that have been linked to heart disease, too.
High Blood Pressure (HBP), a.k.a. Hypertension
Every time your heart beats, it produces the pressure required to move your blood through your blood vessels to the rest of your body and then back to your heart. When your blood pressure rises above normal levels, your heart and blood vessels have to work harder.
Over time, your heart muscle will thicken and stiffen, so it works less efficiently. HBP also damages your blood vessels and helps trigger the accumulation of plaque that eventually lead to the dangerously narrowed arteries that are responsible for heart attacks.
First, a quick cholesterol primer. Cholesterol gets a bad rap, but did you know it serves several important functions? Produced in the liver, cholesterol helps your body make cell membranes, vitamin D, several hormones, including testosterone and estrogen, and more. Your body produces nearly all the cholesterol it needs. But a poor diet and lack of exercise can raise your cholesterol to unhealthy levels.
There are two kinds of cholesterol:
- Low-density lipoprotein (LDL) cholesterol, often referred to as “bad” cholesterol
- High-density lipoprotein (HDL) cholesterol, or “good” cholesterol
Your goal is to keep your LDL down because it’s a contributor to heart disease. It’s the type of cholesterol that clogs your arteries. At the same time, you want to maintain higher levels of HDL cholesterol so that it can do its job: ferrying excess LDL to the liver to be processed as waste. Think of HDL as your body's bouncers—they help control the cholesterol crowd.
These are the cholesterol numbers you want to achieve:
- Total: Under 200
- LDL: Under 100
- HDL: 60 or higher
Obesity, smoking, diabetes, and age all increase risk of having unhealthy cholesterol levels, while diet, exercise, and medications can help you keep it in check. High cholesterol can also run in the family, a genetic disorder called familial hypercholesterolemia.
Excessive body weight has a number of negative consequences. It causes inflammation, which contributes to a rise in your LDL, or bad, cholesterol. Your blood pressure will also rise with your weight, as your heart works harder to pump blood. It also can cause a rise in blood sugar levels, putting you at higher risk of developing type 2 diabetes, another major risk factor for heart disease.
Fortunately, even small drops in body weight—we’re talking about losing as little as 3% to 5%—can help you reduce some risk factors for heart attack, including high cholesterol and blood sugar, which tend to improve with weight loss, according to the Mayo Clinic.
Some doctors still use body-mass index (BMI) to measure obesity. Many researchers don’t like using this height-weight ratio because it doesn’t account for super-fit, muscle-bound people whose BMI may rise into supposedly unhealthy levels. But even though BMI can't tell the whole story about your health, the general rec is to aim for less 25, the cut-off for being overweight. A BMI of 30 and above indicates obesity.
Another critical factor is waist circumference, a measure of abdominal fat. Fat that accumulates around the organs in your middle, like your pancreas and liver, has been linked to diabetes, heart disease, and, yes, heart attacks. To lower your heart attack risk, maintain a waist size of less than 40 inches if you are a man, and 35 inches if you are a woman.
Both type 1 and 2 diabetes heighten your risk of heart attack because, over time, higher than normal blood sugar levels damage the blood vessels and the nerves that control your heart. All that excess blood sugar leads to inflammation, a prime suspect behind atherosclerosis.
Diabetes also makes you likelier to develop both HBP and high cholesterol, among the major contributors to heart attack. Smoking and diabetes are a particularly dangerous combo because both dangerously narrow your blood vessels. Managing your diabetes, with medication and lifestyle modification, must be a priority in order to help prevent a heart attack.
When you don’t sleep well, your blood pressure tends to rise, as does inflammation. Both increase your risk of heart attack. Some research suggests that poor sleep also leads to poor food choices, meaning you may be more likely to overeat or overindulge in junk food.
For example, a study in Journal of the American Heart Association found that women who tossed and turned for an hour or more before falling asleep ate more high-calorie foods than women who drifted off in less than 15 minutes. Overeating, of course, will cause you to pack on pounds and contribute further to heart attack risk factors, like high cholesterol and obesity, as well as worsening blood pressure.
Poor sleep also makes you more prone to type 2 diabetes. Common sleep disorders include obstructive sleep apnea, a sleep disorder that briefly interrupts your breathing repeatedly through the night, and insomnia, which can be chronic. But here’s some good news: Improving sleep may help you eat a more heart-healthy diet.
Lack of Exercise
Exercise has a VERY long list of heart health benefits. First up: Exercise can help lower your blood pressure by strengthening your heart muscle, which means it doesn't have to work as hard to pump. In fact, exercise may be just as helpful several types of blood-pressure medications, including ACE inhibitors, beta blockers, and diuretics, according to a British Journal of Sports Medicine review of nearly 400 studies.
Exercise also increases your HDL cholesterol and lowers your triglycerides, another type of blood fat that, when elevated, contributes to heart attack risk. How exercise does this is not clear, but it may be that all your running, stair-climbing, or biking does exactly what you hear it does: It burns fat, including the fat in your blood.
But, that’s not all. Both cardio workouts and resistance training help keep your blood-sugar levels in check, which will protect against type 2 diabetes. Regular workouts—aim for a minimum of 150 minutes per week—allow you to better manage your weight, reduce stress and inflammation, sleep better, and, as you get in better shape, may encourage you to quit smoking. Yeah, it's pretty much magic.
Are There Uncontrollable Risk Factors for Heart Attack?
It’s true, there are some risk factors for heart attack that none of us can change. They include:
You can’t dial back the clock, unfortunately. Once you reach retirement age your odds for having a heart attack automatically rise. That’s because most heart attacks occur at age 65 or older.
Why? The arteries tend to become less flexible as we age. They stiffen or harden, and that makes blood pressure more likely to rise. Improving how you live your life, through regular exercise, a nutritious diet, and other healthy lifestyle choices, can help offset some of the changes due to age.
But while increasing age ups your heart attack risk, don’t think you’re off the hook if you haven’t yet turned 50. In the past 20 years or so, the number of heart attacks has been on the rise in young people, particularly women, according to a study published in the Journal of the American Heart Association. The reason may be rising rates of diabetes and HBP among younger people in the U.S., especially among women. Obesity, another heart attack risk factor, is also more common among young women.
Just because someone else in your family had a heart attack doesn’t mean that you will have one, as well. However, it may put you in a higher risk category, particularly if that family member had heart disease early. So, if your dad or brother had a heart attack before age 55, or your mom or sister before age 65, you may be at greater risk, too.
Why? Because the genes you got from your parents may code you for heart attack risk factors like abnormal cholesterol levels and HBP. But bad habits, like smoking and poor diet, often run in families as well.
This is a condition that can strike during pregnancy, often characterized by high blood pressure and damage to the organs, usually the liver or kidneys. Blood pressure may remain elevated, even after giving birth, and having preeclampsia can put a woman at a higher risk of heart attack for the rest of her life.
While the link between preeclampsia and heart disease is not well understood, it’s something to be aware of—and address. How? If you’re planning a family or are expecting a baby right now, talk to your doctor about your current heart disease risk factors, including your family health history and lifestyle, such as your diet and exercise habits. And if you do develop preeclampsia, work closely with your doctors to monitor your risk going forward.