The question of which are the most important risk factors in developing silent heart disease comes down to a simple proposition: nature versus nurture, which is a shorthand way of saying genetic and inherited factors, or what you’re born with, versus environmental factors, or things that have to do primarily with your lifestyle circumstances and choices.
The answer to the simple question of what is nature and what is nurture, however, is messy. If only it were as easy as labeling this risk factor as inherited and that one as caused by lifestyle habits and routines (conscious or unconscious). Take, for example, the risk factor of high low-density lipoprotein (LDL) cholesterol (the bad kind). Yes, there’s a genetic component to high LDL cholesterol. If one of your parents had it, you’re at an increased risk for having the condition too, and even more so if both parents had it. On the other hand, lifestyle choices play a key role in whether you actually develop it at all or to what degree it manifests in your life. The same is true for high blood pressure, diabetes, and chronic kidney disease—all high-risk factors for developing silent heart disease (and coronary artery heart disease in general).
On the other hand, take a condition like obesity. There’s no doubt that lifestyle choices contribute to unhealthy excess weight, including eating a diet high in fat, sugar, and salt, not to mention living a sedentary lifestyle. Yet there appears to be an inherited component to obesity. Studies of identical twins—those rare human beings who are genetic clones of one another and make the perfect subjects for human medical studies—have shown that even twins raised in separate households with radically different diets and lifestyles tend to have excess weight if one or both biological parents were overweight.
The same is true for substance abuse. Research in the last decade has indicated that there is a genetic component to drug and alcohol addiction. Yet, undeniably, lifestyle choices contribute to the eventual outcome of whether someone at risk actually succumbs to the disease of addiction. Things get really messy when you also ask how much the genetic component of addiction is influenced when an individual is raised in a household in which one or both parents were addicts. When parents consume drugs or alcohol excessively in front of their kids and the kids later become addicts, is nature or nurture at work?
Interestingly, Swedish researchers a few years ago took a crack at the nurture-versus-nature risk factors of heart disease. In a comprehensive study, they examined the health records of all 80,214 children born in Sweden after 1931 who were adopted, along with the records of their biological parents and their adopted parents. The results? Adoptees were more likely to have had a heart attack, angina (chest pain), or another manifestation of clogged coronary arteries if they had a biological parent with one of these conditions than if an adoptive parent did. The odds were even higher if both biological parents had heart disease. Score one for nature.
But that’s Sweden. The United States is a vastly bigger nation with much greater disparity in wealth, a far more ethnically diverse population, a vastly different and differentiated geography (physical environment), and a markedly less healthy diet (for the average resident). To paint the difference in broad strokes, Swedes rank twelfth among the nations of the world in overall life expectancy, with its citizens enjoying an average life expectancy of eighty-one years; the United States ranks fortieth, with an average life expectancy of seventy-seven years. As for obesity rates among its citizens, Sweden ranks twenty-first, with 9.7 percent of its total population classified as clinically obese; the United States ranks first (sigh!), with a 30.6 percent obesity rate. Even when considering access to health care as measured by the number of physicians per 1,000 people, there’s a vast chasm between the two nations, with Sweden ranked fourteenth (3.3 per 1,000 persons) and the United States ranked thirty-first (2.3 per 1,000 persons). Are we comparing Swedish apples with American oranges (so to speak)?
In Part II, we boldly cross the DMZ of indecision and attribute the major risk factors for developing silent heart disease to either nature or nurture—with the understanding that there will be a good deal of overlap. Ultimately, your risk factors for developing silent heart disease are individualized and personal, depending on a host of factors specific to your profile. We’ll create your own personalized silent heart disease score in Part IV of the book. In the meantime, in this next section of the book, we brave the world of potential risk factors—genetic and environmental.