Map of life expectancy at birth from Global Education Project.

Friday, June 23, 2006

Public Health 101

Actually, for people who have studied public health, this is the first lecture -- but it seems appropriate at this juncture. I'll try to bring some value-added from my own perspective.

In 2004, in JAMA, Mokdad et al updated a famous analysis from 1993 by McGinnis and Foege. You can read the article here, but you will have to go through a fairly laborious registration process in which you reveal your innermost secrets. It might be worth it because you will then have access to all JAMA content that's more than 6 months old.

Anyhow, here's the basic idea. Doctors code a cause of death on the death certificate. Now, this is always a bit dodgy. In nearly 100% of cases, the proximate cause of death is cardiac and/or respiratory arrest -- your heart stops beating, you stop breathing, Jack you dead. For people on life support, it's a bit more complicated. They are first diagnosed as brain dead, then the techies pull the plug. So in those artificial cases, it's cessation of brain stem functioning. In absolutely 100% of cases, the distal cause of death is birth. We're mortal. We're doomed. It is impossible to save anybody's life.

However, the "cause of death" is supposed to represent whatever disease or trauma the doctor considers to be principally responsible for the person dying at this particular moment. In other words, if you didn't happen to have lung cancer, you would have lived longer. Of course this is often something of a judgment call. People who are sick and debilitated for whatever reason often die of pneumonia, but is pneumonia the cause of death or is it whatever made you so debilitated?

In 2000, the leading cause of death in the U.S., according to death certificates, was heart disease (710,760 deaths, 258.2 per 100,000 population). The following causes were, in order, malignant neoplasm (they could just say cancer but that wouldn't seem so learned), cerebrovascular disease (stroke), chronic lower respiratory tract disease (mostly meaning emphysema), unintentional injuries, diabetes, influenza and pneumonia, Alzheimer disease, kidney disase, and septicemia. Then of course there is the famous "other."

Now, this is already fairly questionable. Our friend Rick Lippin is going to jump all over that "influenza and pneumonia" thing, as well he should, on the grounds that few people die of those causes in the U.S. who aren't already very sick. For example, they might have Alzheimer or cerebrovascular or heart disease. So who qualifies for the I&F cause instead of one of those? It is in part a function of the physician's whim, no matter what anybody tries to tell you. Similarly, many people who die of heart disease have diabetes, which is a risk factor for heart disease. Septicemia -- "blood poisoning" or toxic shock -- may be a sequel of an injury or general debility. It isn't entirely clear what ought to have precedence.

Anyway, what McGiniss and Foege, and their successors Mokdad et al did was to push the causes of death further back, toward factors that mostly lie outside the disease process within the body. Most of these they call "modifiable behavioral risk factors," meaning they are dumb stuff the dead people did that caught up with them.

Their top cause of death is tobacco (435,000 fresh corpses in 2000), followed by "poor diet and physical inactivity," alcohol consumption, microbial agents, toxic agents, motor vehicle, firearms, sexual behavior, and illicit drug use. Now, you should immediately notice some conceptual inconsistency here. The vast majority of those deaths from sexual activity result from microbial agents, or more specifically one, Human Immunodeficiency Virus, but they separated them out. (They also note, in a sop to Rick, that "Because pneumonia and septicemia occur at higher rates among patients with cancer, heart disease, lung disease, or liver disease, some of these deaths really are attributable to smoking, poor diet, and alcohol consumption." But that's just tough shit, they're leaving them in.)

This is what we call a paradigm shift -- from the medical paradigm, whereby disease and death are functions of processes that go awry or organs that fail us within our bodies -- to the public health paradigm, whereby they are functions of our behavior and our environment that can be modified before we ever think of the idea of medicine. It is not a bright line, certainly. I invite everyone to have all sorts of fun nitpicking and deconstructing both lists.

While you do that, I'm going to take one step further back. Why do people smoke? Does the evil lie in the herb Nicotiana tobacum? Does it lie in the fool on the other end of the fire? Or does it lie in the multi-billion dollar business corporations and their investors and executives who persuaded people to smoke through a century-long campaign of manipulation and lies?

We might ask many similar questions. Why do people have poor diets? Why are they physically inactive? Why do so many people die in motor vehicle crashes? Why are we exposed to toxic agents (other than Nicotiana tobacum)? Why is sex unsafe for some people? Why are some people at the wrong end of a bullet? And so on. It is this broader frame, the sociological frame, that motivates Stayin' Alive. So-called health care is one of the many things of value that is unequally shared. But it's not the most important. Furthermore, it is not only of value to the recipient - others benefit, such as physicians who draw income and prestige from their profession; hospital executives, who even when they work for non-profit organizations make enormous salaries; drug and medical device company executives and investors; and so on. Because of these other interests, medical services sometimes do not benefit the recipient at all. The medical institution is embedded in society and is a social institution. It also is subject to sociological scrutiny. So that's what we're trying to do here.

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