I understood why I needed to complete the full course, of course. What I didn't understand was why a full course took precisely seven days. Why not six, eight or nine and a half? Did the number seven correspond to some biological fact about the human digestive tract or the life cycle of bacteria?
My doctor seemed smart. She probably went to one of the nation's finest medical schools, and regardless of where she trained, she certainly knew more about medicine than I did. And yet, as I walked out of the emergency room that night with my prescription in hand, I couldn't help but suspect that I'd just been treated with magic.
Certain numbers have magical properties. E, pi and the Fibonacci series come quickly to mind — if you are a mathematician, that is. For the rest of us, the magic numbers are the familiar ones that have something to do with the way we keep track of time (7, say, and 24) or something to do with the way we count (namely, on 10 fingers). The "time numbers" and the "10 numbers" hold remarkable sway over our lives. We think in these numbers (if you ask people to produce a random number between one and a hundred, their guesses will cluster around the handful that end in zero or five) and we talk in these numbers (we say we will be there in five or 10 minutes, not six or 11).
But these magic numbers don't just dominate our thoughts and dictate our words; they also drive our most important decisions.
Consider my prescription. Antibiotics are a godsend, but just how many pills should God be sending? A recent study of antibiotic treatment published in a leading medical journal began by noting that "the usual treatment recommendation of 7 to 10 days for uncomplicated pneumonia is not based on scientific evidence" and went on to show that an abbreviated course of three days was every bit as effective as the usual course of eight.
My doctor had recommended seven. Where in the world had seven come from?
Italy! Seven is a magic number because only it can make a week, and it was given this particular power in 321 A.D. by the Roman emperor Constantine, who officially reduced the week from eight days to seven. The problem isn't that Constantine's week was arbitrary — units of time are often arbitrary, which is why the Soviets adopted the five-day week before they adopted the six-day week, and the French adopted the 10-day week before they adopted the 60-day vacation.
The problem is that Constantine didn't know a thing about bacteria, and yet modern doctors continue to honor his edict. If patients are typically told that every 24 hours (24 being the magic number that corresponds to the rotation of the earth) they should take three pills (three being the magic number that divides any time period into a beginning, middle and end) and that they should do this for seven days, they will end up taking 21 pills.
If even one of those pills is unnecessary — that is, if people who take 20 pills get just as healthy just as fast as people who take 21 — then millions of people are taking at least 5 percent more medication than they actually need. This overdose contributes not only to the punishing costs of health care, but also to the evolution of the antibiotic-resistant strains of "superbugs" that may someday decimate our species. All of which seems like a rather high price to pay for fealty to ancient Rome.
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http://www.nytimes.com/2010/10/17/opinion/17gilbert.html?hp=&pagewanted=print
