The bodies in the labs belonged to teenagers who had died suddenly in car accidents, had been killed, or had committed suicide. Upon examining the bodies, researchers noticed that a surprising number of the teens carried a biological time bomb set to detonate later in life: fatty deposits in blood vessel walls. Those deposits can lead to deadly heart disease, the biggest single killer of Americans. One-third of all teenagers will eventually die from heart disease, according to the American Heart Association.
Although symptoms of heart disease rarely occur until age 50 or later, the hundreds of subjects examined in the “Pathological Determinants of Atherosclerosis in Youth” (PDAY) study mentioned previously show that the buildup of fatty deposits is already happening in many young people’s cardiovascular systems. “The process begins in childhood and progresses throughout life,” says Dr. Rae-Ellen W. Kavey, a pediatric cardiologist at the National Heart, Lung, and Blood Institute in Bethesda, Md. Luckily, heart disease can be slowed and even reversed.
A quick tour of the circulatory system is important for understanding how heart disease strikes. The heart is a muscular pump about the size of your fist. It pumps blood through an intricate network of rubbery tubes (blood vessels) that wind their way to every body part. The blood flowing through large vessels called arteries is laden with the oxygen and nutrients that body tissues need. The blood drops off this vital cargo and flows back to the heart through veins. Blood draining from tissues also carries waste products, which are filtered through other organs and removed from the body. All of the body’s blood vessels, along with the heart, make up the circulatory system.
For the blood to circulate, the tubes that carry it need to be open. In a process called atherosclerosis, a fatty material called plaque builds up on artery walls and narrows the lumen, or empty space, of the vessels (as seen in the subjects of the PDAY study on page 28). The arteries that supply blood to the heart, called the coronary arteries, are especially crucial. They are narrow, so even a small amount of plaque buildup can dramatically constrict the channel. A clot can form, completely blocking the narrowed artery. After just a few minutes without blood flow, the affected heart muscle cells can die, producing a heart attack. The attack may kill or disable a person, depending on the extent of injury to the heart muscle.
Controlling the Risk
Almost all teenagers in the United States have fatty streaks in their arteries that signal the beginnings of atherosclerosis, the PDAY study demonstrated. But the severity of the damage to the coronary arteries depends on certain risk factors, says Dr. Henry McGill, a pathologist at the Southwest Foundation for Biomedical Research in San Antonio, Texas. The important risk factors that you can control are high blood pressure (hypertension), diabetes, obesity, high blood cholesterol, physical inactivity, and cigarette smoking.
Blood pressure is the force that blood exerts as it pushes against artery walls. Blood pressure is measured in millimeters of mercury and includes two numbers. The first is the systolic blood pressure, taken when the heart beats; the second is the diastolic pressure, the pressure when the heart relaxes between beats. Hypertension occurs when either number is higher than normal–that is, higher than 120/80 for an adult. (The cutoff is lower for teenagers because blood pressure generally rises with age.) If the blood’s force is too great, the heart has to work overly hard. Hypertension can also stimulate the development of plaque, although scientists are not yet sure how.
Hypertension, not common in teens before the 1990s, is now appearing more often in young people, primarily those who are overweight. More young teens are also developing diabetes, a disease in which levels of blood sugar are high. That can harm the heart, Kavey says; again, diabetes is often associated with excess weight. As a result of those trends, today’s teens may start having heart attacks in their 30s or 40s, a decade earlier than today’s adults usually do. “That’s terrifying to me,” Kavey told Current Health.
Besides its association with high blood pressure and diabetes, being overweight is risky for the heart for other reasons, in the PDAY study, the subjects who were obese (significantly overweight) had almost twice as much plaque in their coronary arteries as did the teens who were not overweight.
Another type of fat can be a problem for the heart: cholesterol, a soft, waxy substance found in the blood and in all body cells. The body makes its own cholesterol and gets some from animal-derived foods such as meats, eggs, and high-fat dairy products. Too much high-fat food intake can raise cholesterol levels and contribute to plaque development.
Stop Heart Disease Before It Starts
Eating heart-healthy foods and becoming more active can greatly reduce the chances of developing heart disease. In a 2004 study, researchers from Hong Kong and Australia put 82 overweight children ages 9 to 12 on either a low-fat diet alone or a low-fat diet plus weekly exercise for a year. In the children who stuck with the diet and exercise program, researchers saw reductions in the thickness of the walls of the carotid arteries, the chief arteries in the neck. (Thicker walls mean more fatty buildup.)
Looking once more at the PDAY study, the risk factor associated with the most plaque buildup was smoking. Avoiding cigarettes is probably the single most important thing a young person can do to preserve healthy arteries for a lifetime.
Most teens don’t know what the insides of their arteries look like, but they would be wise to learn from those who’ve had their time bombs exposed. It’s possible to add decades to the timer, research shows. “If you control these risk factors for life, just a modest reduction [in risk] will dramatically affect the development of coronary heart disease,” McGill says. The time to start is now.
Change Your Life Make your heart healthier by changing the way you live.
Aim to work out for 30 minutes to an hour most days of the week.
Try walking, dancing, cycling, swimming, shooting baskets. or raking leaves. Exercise can make your heart stronger and your circulatory system more efficient. It can also lower the amount of cholesterol in your blood, help you lose weight, and keep your blood-sugar levels down.
Improve your diet.
Eat foods low in cholesterol and saturated fat. (See “Chewing the Fat.” page 19, for more information on fats.) Eat more wholegrain breads, pastas, and cereals and fresh fruits and vegetables.
Smokers are two to four times as likely to die of heart disease as nonsmokers, according to the American Heart Association. Nicotine narrows the arteries, and other chemicals in cigarette and tobacco smoke promote plaque buildup and the formation of blood clots that can block an artery, leading to a heart attack.
Monitor your weight.
Shedding excess pounds can normalize high blood pressure and reduce the risk of diabetes. Maintaining a healthy weight directly protects the heart.
JAMMED UP Keep these images in mind the next time you think about ordering that super-crispy fried chicken and double-fudge sundae! The image on the left shows a healthy heart artery, with plenty of space in the lumen for blood to flow. On the right, however, this teen’s artery was so plugged up with plaque, blood had almost no room to squeeze through.
* Which of the body’s systems do the heart and blood vessels form? (the circulatory system)
* How does a heart attack happen? (Cholesterol forms plaque along the walls of blood vessels in a process called atherosclerosis; when plaque clogs the coronary arteries, heart tissue dies, causing a heart attack.)
* Look at the image of the 18-year-old’s artery on page 28. If the subject had not died young of unrelated causes, what could you infer about his future health? (With the lumen barely wide enough to let blood pass through, the subject would probably have developed heart disease or suffered a heart attack in the decades ahead.)
Have the class find definitions for some heart- and heart disease-related terms that weren’t in the article. Examples might be capillaries, cardiac arrest, congestive heart failure, coronary heart disease, hypercholesterolemia, myocardial infarction, and stroke. Students can then create a puzzle or quiz using those terms and others from the article.
The University of Texas Health Science Center at San Antonio, which conducted the study of atherosclerosis in deceased teens that is mentioned in the article, has a full curriculum for teachers. Visit teachheahhk-12.uthscsa.edu/curriculum.htm#h, and click on Cardiovascular System.
Even if your students can’t visit “The Giant Heart” at the Franklin Institute Science Museum in Philadelphia, they can still learn a lot of facts and trivia from the accompanying teacher’s guide: sln.fi.edu/tfi/exhibits/heart_teacher_guide.pdf.