Statistics and Scare Tactics: Pet Peeve

You know, I think that with the exception of RA (and maybe people who don't appreciate port... okay, and people who park like douches... and VA Tech fans... and... well, nevermind), nothing pisses me off more than the use of scare statistics -- those statistics that inculcate fear rather than education or knowledge on the part of those who hear them.

Let me give you a good (i.e., totally shitty) example of one such report that I read today. It comes from a Johns Hopkins medical alert: 

The association between rheumatoid arthritis (RA) and cancer is not completely clear. Some studies show an increased risk of cancer in people with rheumatoid arthritis (RA) while others show a decreased risk. But the picture becomes clearer when researchers look at specific cancer types.

Lymphoma. The strongest evidence of a link appears to be between lymphoma -- the most common type of blood cancer -- and severe rheumatoid arthritis (RA). Researchers from Sweden examined data from nearly 75,000 RA patients, 378 of whom had lymphoma. The researchers assessed risk for three different levels of disease activity (low, moderate, and severe) and found that people with moderate disease activity were eight times more likely to have lymphoma than those who had low disease activity, while those with severe disease activity were 70 times more likely.

More support for a connection comes from a review of 21 published studies, including the Swedish study and 13 others that tried to determine whether there was a link between lymphoma and rheumatoid arthritis (RA). The findings, reported recently in Arthritis Research & Therapy, showed that overall, people with rheumatoid arthritis (RA) were twice as likely as the general population to develop lymphoma, particularly Hodgkin's lymphoma (one of the most curable types of cancer when detected early).

Lung cancer. The same review also reported that lung cancer was observed more often in people with rheumatoid arthritis (RA). Based on data from 12 studies, people with rheumatoid arthritis (RA) were 63% more likely to develop lung cancer than the general population.

Okay, so you read these statistics, and you get alarmed: "Holy shit! Oh Em Gee! I have RA! I'm going to get lymphoma or lung cancer!"

Now, I'm not saying you're not going to get one of those diseases, but the statistics that Johns Hopkins has provided are next to meaningless because they omit some incredibly critical information: namely, the incidence of each disease in the general population.

Huh? F*ck the what are you talking about, Kim?

Well, according to the lung cancer study, people with RA are 63% more likely to develop lung cancer than the general population. Oooh: scary. But, what's the incidence of lung cancer in the general population? For example, if it's 1 in a million, are you going to be worried about having a 1.63 in a million chance of developing lung cancer over your lifetime? Hardly.

Want to know what the relevant stats are? For men and women combined, in the general population, there is a 1 in 14.5 chance of developing lung cancer, which calculates to a 6.9% chance of developing said cancer. Thus, for RAers, who are 63% more likely to develop lung cancer than the general population, there is an 11.2% chance of developing lung cancer. RA increases the risk of developing lung cancer by 4.3 percent. RAers thus have about a 1 in 10 chance of developing lung cancer. It's not quite so scary now, is it? 

And what about Hodgkin's lymphoma (the most common type of lymphoma developed by RAers)? Well, crap. In the general population, there is a 1 in 438 chance of developing said disease. In other words, there is a 0.2% chance of a "normal" person developing Hodgkin's lymphoma. If RAers are twice as likely as people in the general population to develop this cancer, that means RAers have a 0.4% chance of developing Hodgkin's disease. (I'm aware that these stats are not spot on, simply because the article didn't tease out the varying lymphomas. But you get the picture, don't you?)

Mark Twain once famously said that there are three kinds of lies: lies, damned lies, and statistics.

Stop all the worrying, and don't let the statistics damn your life!

Comments

[Wren]

Excellent post. I'm with you on hating the scare tactics. And to what end? Why do they do this to us? What's the point?

Anyway, thanks for walking us through those stats. Nice to know that we don't really need to worry so much. RA is plenty of worry all by itself.

[Kim H]

You know, I'm really not sure why they do this to us. Having a repository of information at your fingertips is great. But you have to know how to process and utilize the information before it can be helpful. I think that's what we're lacking in a lot of scientific reporting today.

[Pollyanna Penguin]

Woohoo! Great post! This is one of my pet peeves too!