Back in March I wrote a blog post asking whether gaining weight makes you taller. Weight and height are clearly associated, and from that data alone one might speculate that gaining weight could make you taller. Of course causation is in the other direction: becoming taller generally makes you gain weight.
In the 1980’s, cardiologists discovered that patients with irregular heart beats for the first 12 days following a heart attack were much more likely to die. Antiarrythmic drugs became standard therapy. But in the next decade cardiologist discovered this was a bad idea. According to Philip Devereaux, “The trial didn’ t just show that the drugs weren’t saving lives, it showed they were actually killing people.”
David Freedman relates the story above in his book Wrong. Freedman says
In fact, notes Devereaux, the drugs killed more Americans than the Vietnam War did — roughly an average of forty thousand a year died from the drugs in the United States alone.
Cardiologists had good reason to suspect that antiarrythmic drugs would save lives. In retrospect, it may be that heart-attack patients with poor prognosis have arrhythmia rather than arrhythmia causing poor prognosis. Or it may be that the association is more complicated than either explanation.