Et AL: Health, Behavior, and Risk

Personalized public health is an oxymoron, but you wouldn’t know that from the evening news or morning headlines. The New England Journal of Medicine recently reported that individuals with elevated levels of C-reactive protein, a non-specific marker of chronic inflammation, were at increased risk of a heart attack. This news ricocheted through the media. C-reactive protein was heralded, in some stories, as a “better predictor” of the risk of heart disease than cholesterol. Usually unsaid was the fact that cholesterol directly leads to heart disease, and you can do something about it (exercise, change your diet, and, if need be, take cholesterol-lowering medications). We have no idea why C-reactive protein gets elevated, why it might predict a heart attack, or what one can or should do about it.

It’s not just the media. Since the human genome was first mapped two years ago, “molecular celebrities” have promised a future in which everyone’s unique DNA is decoded. Once your individual risk for every major disease is known, you’ll be issued a personalized prescription for health-protecting behavior: what you must (or needn’t) do to ensure a maximally healthy lifespan. While this vision seems sane at first blush, it makes little sense!

First, there is a very practical problem. Let’s assume each of us knew precisely what our individualized behaviors should be in relation to the 20 most serious diseases. How would we keep track of all our personalized “dos and don’ts”? With a Palm Pilot? The average elderly American is overwhelmed by his or her medication schedules; timely behavior is a lot more complicated than popping pills “by the clock.”

Second, it ignores the major determinants of behavior: our environment and what those around us are doing. Assume for the moment you have very little risk of obesity and diabetes, but a very high risk of lung cancer (from smoking). Let’s assume my risk profile is exactly the opposite of yours. How are we to behave when together? When I host a dinner, will I light up (along with all the other guests at low risk of lung cancer), while you “just say no”? What about the meetings you organize? If you put chips, cookies, and chocolates on a table during a series of long, boring meetings, everyone will consume enough to gain weight over the long term, some more than others. Given my risk profile, I’d probably develop diabetes. If there’s no food in the room, none of us will.

It’s a lot easier to avoid risky behavior when everyone else does as well, and when the environment doesn’t support it. That’s precisely why tobacco use, red meat consumption, and driving “while under the influence” have dramatically declined in the United States. Our society has changed its cultural mores; everyone has benefited overall, even if some members benefited from different behaviors more than others. But it will never work to tell people, based upon their genetic risk, that they cannot smoke or stuff their mouths while those around them can.

A third and final point: Except for rare diseases in which a single gene determines whether you do or don’t get ill, the vast majority of illnesses are complex and polygenic in origin, and any one person’s “risk” is relative. An elevated C-reactive protein (or particular genetic makeup) might double one’s risk of heart disease, but that does not mean most people who develop heart disease will have an elevated C-reactive protein (or its genetic equivalent). When everyone pursues a healthy lifestyle, each will benefit from his or her own exertions and from the common, mutually supportive communal behavior.

One hundred years ago, the most common threat to health was infection. We tackled contagion effectively, and communally, through better sanitation, clean water supplies, and universal immunization. Today, our greatest threats to health are behaviors that result in diabetes, heart disease, cancer, and stroke. A personalized drug regimen is appropriate since drugs are expensive and carry risks. A personalized list of screening procedures (colonoscopy, Pap smears, mammography) and their frequency might one day be appropriate as well, since they are expensive, inconvenient, and may carry unneeded risk. When it comes to health-protecting behavior, however, the communal approach is the best prescription. Communal attention to healthy behavior is risk-free, inexpensive, and mutually reinforcing.