A recent New York Times story by Nicholas Bakalar, of their better health writers began by giving examples of different ways of communicating the same statistic regarding the value of an intervention: a 50% reduction in risk, a reduction in risk from 2% to 1%, or one of every hundred people getting the intervention is saved from the outcome. He points out that the choice of which of those to tell someone will affect what he thinks of the intervention. This is one of those facts that is well known to those of us who do research on risk, but that guru consultant types who half understand it charge a fortune to teach to corporate types (not that I am bitter or anything). Bakalar does a decent job of explaining it and getting it right, though he uses some awkward terminology.
The story was motivated by some new review study of the research that demonstrates this phenomenon, but that is not at all interesting because, as I said, those of us familiar with the subject already knew the information. Perhaps the review includes something new, but such articles usually do not, and I am doubtful enough to not want to even bother to look it up. More interesting is Bakalar closing the article with a quote from the study author,
Journalists have to be careful about press releases with ‘new’ or ‘groundbreaking’ studies presented with relative risk reductions. For example, a study might claim a risk reduction of 50 percent. If the risk goes from 20 percent to 10 percent, that’s impressive. If it goes from 4 percent to 2 percent, it’s not. And both of them are 50 percent reductions.
The latter part of that is wrong in the sense that it is overly simplistic, suggesting that the study author does not really know what he is talking about, another good reason to not bother to read the study. If the risk of, say, having one’s BMI increase to 25 sometime in the next decade goes from 20% to 10%, that is quite likely not consequential for health outcomes. If the risk of having your brain eaten by zombies in the next week drops from 4% to 2% I would say that is tremendously important good news.
But the first bit of the quote is good advice. It is one of the many reasons to not get too excited about “groundbreaking” research. Even better advice would be to consider the risk in terms of overall health risk, rather than in terms of one disease in isolation. Increasing the risk of brain cancer by 20% (which sounds more impressive than a relative risk of 1.2, which is why they put it that way) caused by using a cell phone at an extreme level has a very trivial effect on someone’s overall risk of getting a fatal cancer. But I doubt that NYT reporters are going to pick up on this advice from their own paper, let alone more complicated points like the one I made.
Of course, Bakalar himself might have been more cautious about how “new” the study he reported on really was, given that it seemed to contain absolutely nothing new.
Of course, maybe reading The Onion would be better still, since it recently reported the headline,
Study: All American Problems Could Be Solved By Just Stopping And Thinking For Two Seconds
That really could eliminate a lot of bad health reporting, in ways that I have noted in this series (“what does that even mean?” “is that really possible?”). It might, however, have gone a bit far in claiming:
“We found that in 93 percent of cases, a positive outcome could have been achieved if Americans simply splashed a little water on their faces.… Our data indicate that when U.S. citizens don’t take a second to compose themselves, they typically charge in like maniacs and hurt either themselves or several million Iraqi civilians.” Mallory said a good rule of thumb for Americans is to think of a plan, stop, and then do the complete opposite.
This advice is probably far too harsh even for health reporters, though maybe it is about right when NYT reporters are writing about anything Bloomberg says about health. Though the same is true for their counterparts in the UK are reporting about alcohol, or those in India are writing about tobacco this is clearly an international problem).