In consideration of your glaze-eyed tryptophan coma — at least among those who weren’t frightened off by the MRSA-in-turkey news — today’s post is mostly composed of brightly colored pictures. (Also, speculation. You’ve been warned.)
About a week ago, a nonprofit research group called Extending the Cure published the latest in a fantastic series of maps they have been producing for several years, based on public and privately collected data. Earlier iterations have looked at the incidence of various resistant organisms over time. This time, they decided to look instead at the major drivers of resistance, and focused on national data about antibiotic prescriptions, broken down by drug type and by state between 1999 and 2007.
The graphics they produced document both a troubling growth in the use of some precious (because still effective) antibiotic classes, and also a surprising differential in the amounts of antibiotics prescribed in different parts of the country. The rate of use of antibiotics, measured by outpatient prescriptions per 1,000 inhabitants, varied from a low of 533 in Alaska to a high of 1,214 in West Virginia.
When those usage rates were mapped, they looked like this to the right: A strand of states that runs through the Southeastern United States and along the Appalachians lights up for antibiotic overuse. That regional differential — along with an obvious pattern of greater use in the entire eastern US, compared to the west — is certainly what caught the eye of the media when the maps were released, with stories such as this one in USA Today pointing out the left-to-right shift.
So. Well. I am a member of the media, and I do see that story in this map. But I am also a public-health person, and looking through those lenses, I see something a little different (and so I am sure does every other public health-person who is reading this post and waiting impatiently for me to Just Get To The Point, Maryn).
Here’s what I see: The states that map to the greatest antibiotic use happen to be the same states that also map to the worst health status in the US — the greatest incidence of obesity, asthma, tobacco use, heart disease, heart attack, diabetes and stroke. Down here in the South, we not-so-jokingly call those states the Stroke Belt; Atlanta, where I live most of the time, is essentially the buckle.
Here, for instance, is what stroke deaths looks like, in a map from the National Stroke Mortality Atlas, produced by the Centers for Disease Control and Prevention. (In this map, the Extending the Cure map, and all the maps that follow, the darkest color represents the greatest incidence, whether or not a legend specifies so.)
Here’s a map of diabetes incidence in 2008, produced by the fantastic Slate Labs visualization project and based on data gathered by the CDC.
Here’s one of obesity — BMI greater than 30 — in 2010, generated by the seriously useful map engine attached to the data vault of the CDC’s Behavioral Risk Factor Surveillance System (BRFSS) project.
So what’s going on here? Let’s stipulate that correlation is not causation. Even so, it’s a bit of a mystery.
It is not new news that West Virginia, Kentucky and Alabama — and to a lesser extent, Tennessee, Georgia and Mississippi — are seriously unhealthy places. They are notoriously among the poorest states in the US, and with poverty comes the worst access to health care and the greatest incidence of lifestyle diseases.
However, lack of access to health care doesn’t, to me, correlate with higher-than usual amounts of antibiotic use. That doesn’t make sense organizationally or economically; if you can’t access health care, where are you getting the prescriptions from? It doesn’t make sense behaviorally, either. Obesity, diabetes, and cardiovascular disease are health-ignoring behaviors; they are among the things that happen when you don’t take care of yourself. But taking antibiotics is, at least on its face, a health-seeking behavior — after all, to obtain a prescription you must visit a health professional.
I asked Ramanan Laxminarayan, the director of Extending the Cure, what he thought was going on behind this unexpected concordance. He suggested that the antibiotic use might be an effect of poor health status, in that people who have many things wrong with them may go to the doctor more, and may obtain antibiotics — perhaps inappropriately — while they are there. (He is the lead author in research showing a higher rate of antibiotic use during flu season, even though flu is a viral disease which antibiotics cannot affect.)
On the other hand, what if antibiotics cause these other health effects? That lines up with the work of Martin Blaser of New York University, who has proposed that taking antibiotics permanently kills off beneficial bacteria in the gut — and might therefore be responsible for changes in nutrient absorption and for the rise in obesity and diabetes.
As I said up top: This is just brightly colored pictures and speculation. But I’m intrigued, and I’d love to hear reactions from public health readers. Is there something worth interrogating in this correlation between antibiotic overuse and poor health status? Or am I too addled by tryptophan to spot an artifact when I see it?