You can’t do anything about some risk factors for CVD. For example, individuals with a family history of heart disease at an early age are more likely to develop CVD, as are African Americans, and both men and women are at increased risk as they age. But there are many risk factors people of all ages can modify, most significantly through diet and exercise.

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Modifiable risk factors include smoking; a diet high in saturated and trans fats, cholesterol, sodium, and added sugar; a sedentary lifestyle; obesity; excessive alcohol consumption (see Chapter 19 to learn more about health implications of alcohol consumption); and high blood pressure. Having high blood pressure (hypertension)—a condition in which blood pushes with excessive force against artery walls—is correlated closely with the extent of atherosclerosis found in the arteries. (Hypertension is discussed in more detail in Chapter 13.) (INFOGRAPHIC 7.4)

Question 7.3

Though many risk factors for CVD are modifiable, more than 90% of Americans eat a “poor” diet for heart health, according to the American Heart Association. For example, the concentrations of cholesterol and triglycerides in blood are a major risk factor for CVD. Blood cholesterol levels measuring less than 200 milligrams of cholesterol per deciliter of blood (mg/dl)—the standard units of measurement for cholesterol—are considered healthy. Yet the average cholesterol level for a U.S. adult is 200 mg/dl—meaning the average American has a borderline high level. People with high levels of total blood cholesterol have approximately twice the risk of heart disease as those who do not. Normal triglyceride levels vary by age and sex, but anything above 200 mg/dl is considered high. High triglyceride levels are common in people with heart disease or diabetes.

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One of the most important tools Berenson and his Bogalusa study team used to evaluate healthy diets was children’s intake of fat and cholesterol. Besides asking kids about their diets, the Bogalusa researchers also directly measured levels of lipids in their blood, by looking at the lipoproteins that transport lipids around the body. Likewise, physicians use a diagnostic test called a lipid panel to provide information about total cholesterol, high-density lipoproteins (HDLs), LDLs, and triglycerides in the blood.

Recall from Chapter 6 that lipoproteins contain different proportions of proteins, cholesterol, triglycerides, and other components that affect their density and function—as well as their impact on the risk of CVD. The LDLs ferry cholesterol to all of the cells of the body. This cholesterol forms the root of the plaques that slowly constrict blood flow through the vessels that feed the heart and brain; the lower your LDL cholesterol level, the lower your risk of heart attack and stroke. If you have other risk factors for CVD, it’s best to keep your LDL level below 100 mg/dl (some experts recommend levels closer to 70 mg/dl). In some cases, diet and exercise may not suffice, in which case people also take medications that lower their total cholesterol and LDL levels.

HDLs, in contrast, bring cholesterol from tissues back to the liver, where it is processed and eliminated; not surprisingly, higher levels of HDL have been associated with a lower risk of heart disease. In fact, low levels of HDLs—less than 40 mg/dl in men and 50 mg/dl in women—can even increase the risk of CVD. (INFOGRAPHIC 7.5)

Question 7.4

In general, the risk for CVD increases with the number of risk factors you have. People who are carrying around a cluster of some of the most dangerous risk factors for CVD are said to have metabolic syndrome. For example, having an elevated blood glucose level is a serious condition, but when coupled with excessive amounts of abdominal fat and high blood pressure, a person has a greater chance of cardiovascular problems because of the combination of risk factors. Not surprisingly, this makes them much more likely to have a heart attack or stroke, and five times more likely to develop type 2 diabetes. To be given a diagnosis of metabolic syndrome individuals must have at least three of the following problems: excessive abdominal fat, high blood pressure, elevated levels of triglycerides in the blood, low levels of HDL, and elevated blood glucose levels (either prediabetes or type 2 diabetes—see Chapter 5). Furthermore, the prevalence of metabolic syndrome is on the rise. Today, it affects more than 50 million adults in the United States, and approximately 25% of adults worldwide. (INFOGRAPHIC 7.6)

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Question 7.5

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To learn more about the development of CVD, pathologist William Newman and a colleague would drive the 66 miles up from Louisiana State University School of Medicine in New Orleans to Bogalusa to perform the autopsy whenever a young person in Bogalusa died. What Newman and his colleagues saw when they opened the hearts of the young people shocked them.

Although most people think of heart disease as something that affects adults, virtually all of the young people of Bogalusa already had fatty streaks—the precursors to plaques—lining the blood vessels of their hearts. As soon as Newman and his colleagues cut open a vessel, they knew what they were seeing—the streaks “look a bit yellow,” Newman said. By adding a specific dye, he got a better sense of the shapes and sizes of the streaks to confirm his belief. There was no doubt—these children had early forms of atherosclerosis.

To quantify the extent of atherosclerosis, each pathologist would look at every autopsy specimen and assign the stained fatty streaks a score, and the scores were then averaged together. The study was blinded, so the pathologists didn’t know the source of the tissues beforehand.

The researchers then compared the results of those autopsies with data collected from young people during the study, and identified a number of risk factors associated with the risk of early atherosclerosis: smoking, obesity, hypertension, and high levels of cholesterol and triglycerides in the blood.

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When all the known risk factors were considered, a clear pattern emerged: “We found that those individuals who had higher levels of known risk factors on the average had more fatty streaks in their coronary arteries and the aortas than individuals who had lower levels,” says Newman. In other words, though many of them were not even old enough to vote, these young people already had telltale signs of heart disease. Some even had developed full-blown plaques that were beginning to obstruct blood flow. Had these young people lived, those with the higher levels of atherosclerosis would have been at risk for a heart attack or other complications of heart disease.

“The autopsy studies were really landmark studies,” says Peter Katzmarzyk, an epidemiologist at the Pennington Biomedical Research Center in Baton Rouge. Before them, he says, scientists didn’t really understand that things like heart attack and stroke have their genesis in childhood. “The Bogalusa Heart Study really put that on the map,” he says. And it made a strong case that averting severe consequences of heart disease later in life would mean addressing the lifestyle choices we make when we are young.

The science behind the influence of dietary fat and fatty acids on CVD is complex and continually evolving. As early as the 1950s, scientists and the public were talking about the dangers of high-fat diets, particularly those that contain saturated fatty acids—but, recently, we’ve begun to realize the picture isn’t quite so straightforward. (INFOGRAPHIC 7.7)

Question 7.6