When it comes to our health, the term “normal” tends to bring comfort. This spot on my leg, or bump on my arm – is it normal? When the answer is yes, we’re understandably relieved.
But, in terms of statistics, the term “normal” doesn’t necessarily mean good, or even appropriate. It simply describes the bell-shaped distribution of a continuous measure, such as height within a population. Some people are short, some people are tall, but most people are average height, within the so-called “meaty” part of the curve. Cardiovascular health factors such as body weight, blood glucose, cholesterol, and blood pressure follow a similar pattern. Within the U.S. population, there is a normal distribution of each of these health factors. But being part of the norm may not be optimal. It might not even be healthy, particularly in an environment where heart disease is common, as is the case in the U.S.
In the U.S., two out of every three men and one out of every two women will develop heart disease or die from it in their lifetime. Cardiovascular health factors such as high cholesterol and high blood pressure—both of which are abnormal, but still affect one in three U.S. adults—are so common that they are considered nearly unavoidable and simply a consequence of “normal” aging by many physicians and patients. Patients’ numbers inexorably increase with age, the thinking goes, and at some threshold of risk, doctors recommend lifestyle therapy, with lifelong prescription medications often soon to follow.
However, research pioneered by Jeremiah Stamler, MD; Phil Greenland, MD; Martha Daviglus, MD, PhD; Kiang Liu, PhD; Don Lloyd-Jones, MD, ScM; and others here at Northwestern University suggests otherwise. In individuals who do not use tobacco and maintain optimal levels—levels that also leave them outside of the normal range—of body weight, blood glucose, cholesterol, and blood pressure into older adulthood, heart disease occurs at rates far lower than the average person in the U.S. (from one in seven all the way to one in 20, if all risk factors are at optimal levels). These individuals live 10 to 13 years longer, get sick less often, have a better quality of life, and even incur lower lifetime health care costs.
Unfortunately, less than 5 percent of the U.S. population currently has such a combination of optimal health factor levels. Raising this percentage—pushing “normal” closer to “optimal”—will be largely dependent on what researchers term primordial prevention, or preventing abnormal health factor development altogether.
The reason primordial prevention has such a dramatic impact on heart disease death can be illustrated by looking at the limitations of the other prevention strategies: primary prevention, the treatment of abnormal health factors, and secondary prevention, the treatment of heart disease itself.
In the case of primary and secondary prevention, physicians need to screen, detect, and treat individuals with the highest cholesterol levels—those at the tail of the cholesterol population curve—or people who have already developed heart disease.
But here’s where statistics come in: the majority of heart attacks and heart disease deaths will occur in individuals with only mild increases in their cholesterol, many of whom fall below the treatment threshold for effective medications such as statins. Why? Because that’s where the greatest number of people exist within the curve. More than 90 percent of all heart attacks and heart disease deaths occur in individuals with at least one risk factor (cholesterol or blood pressure, for example) that is high enough to increase risk, but many do not have levels high enough to warrant treatment. So, shifting the health factor curve toward optimal levels through primordial prevention leads to far fewer deaths than treating only the tail.
History has shown that addressing even one of these health factors across the population can have a major impact on decreasing heart disease-related deaths. Take cholesterol, for instance. From 1960 to 2002, the average U.S. adult total cholesterol level has decreased from 222 milligrams (mg) of cholesterol per deciliter (dL) of blood to 203 mg/dL, drawing much closer to the recommended level of 200 mg/dL or lower. While the proportion of individuals taking cholesterol-lowering medications has increased from practically zero in 1960, to 3.4 percent in 1988, to 9.3 percent in 2002, these increases alone do not explain the decrease in total cholesterol levels. Instead, these declines in total cholesterol are primarily driven by a reduction in LDL [bad] cholesterol, which is tightly linked to saturated fat (or “bad fat”) consumption. Remember steak and eggs with whole milk as a usual breakfast, as seen on the hit TV series Mad Men? For most, that’s no longer the norm, and researchers have demonstrated that lower U.S. saturated fat consumption has been a key driver of these declines.
Researchers from the University of Liverpool and U.S. Centers for Disease Control and Prevention estimate that these declines in cholesterol levels led to approximately 83,000 fewer heart disease deaths between 1980 and 2000, which turns out to account for nearly one-quarter of the 342,000 fewer heart disease deaths over that 20-year span.
This isn’t limited to the U.S. Other countries, such as Finland, enacted aggressive subsidy programs away from dairy farmers to berry farmers to reduce saturated fat consumption. Finland experienced even greater declines in average cholesterol levels through these curve-shifting primordial preventive efforts. Not surprisingly, fewer heart disease deaths occurred.
Community-wide primordial prevention strategies like this typically fall outside the traditional health sector but can still be very effective. They include indoor smoking bans, advertising restrictions on tobacco, alcohol and unhealthy foods (particularly to children), trans fat bans, salt reductions in the food supply, and state-level tobacco excise taxes. These policies have demonstrated scientific credibility, political acceptability and economic feasibility in order to be successful, yet have been incompletely implemented.
Other potential interventions that have been proposed include additional restrictions on advertising soda and junk food to children, changes to farm and school lunch subsidies to encourage fruit and vegetable consumption, and zoning regulations to promote walking, cycling, or use of public transit to work. Denmark even passed the first “fat tax” in October 2011, taxing 16 krone (roughly U.S. $2.90) per kilogram of saturated fat. Despite calls against such “nanny state” interventions in the U.S., one may recall the changes in social acceptance of previous measures now taken for granted: vaccinations, seat belts, and indoor smoking bans, among others. Today’s “injustice” may be tomorrow’s foresight.
In 2010, the American Heart Association (AHA) announced its Strategic Impact Goals for 2020. In addition to reducing heart and vascular disease death and disability by 20 percent, the AHA targeted a 20 percent improvement in the cardiovascular health of all Americans by 2020. Unfortunately, if current health trends continue, Americans’ cardiovascular health will improve by only 6 percent. Declines in smoking have stalled; body weight and glucose continue to climb; and improvements in blood pressure treatment and control are being wiped out by overweight and obesity.
As Geoffrey Rose once wrote, “sick populations have sick environments.” Primordial prevention strategies aim to make the environment healthier. In addition to robust primary and secondary preventive measures, primordial prevention can and should be an essential element in achieving the AHA’s goal and turning optimal into the new normal.