Saturday, December 08, 2007


This new "study" deserves its very own made-up word--that's how utterly ridiculous and misleading it is.

It's a classic case of distortion, from the headline--"Obese? Drive at Your Own Risk!"--to the bait-and-switch of its conclusion. Based on research involving people in car accidents, it purports to look at how BMI affects your risk of dying in a car accident.

Here's how it opens:

Being obese may increase the risk of perilous diseases like diabetes, heart attack, stroke and cancer. And it can be fatal in one more way -- it enhances the risk of dying in a car crash.

What's the connection? Well might you ask. This is one of those reviews masquerading as a study, where researchers look at data--in this case, data on people involved in car accidents and their BMI.

Researchers divided over 230,000 people into groups based on their body mass index (BMI) . The rate of always wearing seat belts was 82.6 per cent for non-obese motorists (BMI less than 25), 80.1 per cent for overweight motorists (BMI 25-29), 76.6 per cent for obese motorists (BMI 30-39) and 69.8 per cent for extremely obese motorists (BMI 40 and above). The gap climbed from 2.5 per cent for overweight, to 6.0 per cent among the obese, to 12.8 per cent among the extremely obese.

Um, what we've got here is a correlation between not wearing your seat belt and dying in a car crash, along with a statistical analysis of percentage of seat belt wearers and their BMI.

As Sandy Szwarc is fond of saying correlation is not causation. Or, to put it another way: The media is willing, but the evidence is weak.


vesta44 said...

Did they bother to find out if the very obese who didn't wear seatbelts weren't wearing them because the seatbelts didn't fit and they couldn't find extenders? And what number of pounds are seatbelts rated to protect? They'll hold a 200 lb person much better than a 400 lb person, I'll bet. I don't wear my seatbelt, mainly because the shoulder harness part hits my neck (I have the rack of doom, and those things aren't designed for women with serious boobage). I'll take my chances without it, rather than chance being decapitated by it, thank you very much.

Anonymous said...

You read my mind, Vesta. This study is serious crap. It could be used to determine that more tests need to be done to fine a CAUSE, but as of right now, all they have is CORRELATION.

And a stupid one, at that. Fat people don't wear their seatbelts, apparently. As far as this study can tell me, and in fact they're probably trying to imply this, fat people are stupid. I refuse to believe the public will accept that, but of course, that's just me being naive. Gosh, this is why I can't stand to read "scientific" reporting. So few journalists are properly trained to handle it.

Anonymous said...

Wonderful post, Harriet! There are countless things that could be really going on, rather than "blame fat people." One glaring "confounding factor" that leaps out to me is that they didn't control for SES. As we all know, fat people (especially the fattest) are discriminated in the workplace and make lower salaries... hence, they are more likely to have older, cheaper cars and be less able to keep them in tip-top shape. So, the fact they might be injured or die more often in auto accidents could be more reflective of their cars and socioeconomic status, for instance, not their BMIs! And then there's the matter of disparities in medical care...

I have little faith in any data from the BRFSS, as it's based on telephone surveys and rife with inaccuracies in being representative of the population. IF the heaviest really don't wear seat belts as often, might that be also be poor car designs, and reflective of difficulty getting cars and seatbelts that are designed to accomodate them?

Harpy said...

Cars are generally (hell, nearly always) designed to be driven by an average-height slim male. This is patently obvious to pretty much anyone who isn't an average-height slim male. Some smaller cars like hatchbacks are mode with average-height slim women in mind, but that's about the extent of it.

Seatbelts are usually only rated to about 200lbs, I've read. Airbags can be very dangerous to you in an accident if you sit within 12"/30cm of the steering wheel. There are lots of other things that make cars less safe for fat people or tiny people or women and so on.

My fat grandmother had to get a medical certificate exempting her from wearing a seatbelt (it's the law everywhere here) because she was also short and the belts cut into her jawline. Some cars have adjustable belt height positioners now which is a small improvement.

Anonymous said...

The more I think about the slant of this study and that newspaper coverage (more piling on that fat people are behaving badly and need health education), the more upsetting it is. There was no attempt to offer helpful information.

I just found this. Elizabeth Morris Fisher has been a one-woman advocate in trying to get changes in federal guidelines for the manufacture of seat belts and appealed to the National Highway Transportation and Safety Administration. She created a website of automobile manufacturers making seat belt extenders available for free or at a nominal cost:
Seatbelts for Larger Passengers

Carrie Arnold said...

You all read my mind.

Sandy- thanks for the link- that's wonderful that people are doing that.

I mean, technically, people with short legs (like me and everyone in my family) are more likely to die in a car accident because we have to sit so close to the steering wheel to reach the pedals.

We know that seatbelts save lives. That extenders (or seatbelts with better designs) are more common is terrible.

Harriet said...

Thanks for that link, Sandy. Looks very interesting. I'm learning to decode these studies from you!

harpy and Carrie, you're right about cars being dangerous to all kinds of people. I tend to worry about this because I'm five foot one and sit practically on top of the steering wheel in order to see over it. (And am getting to the point where I may need a pillow!)

But this article and research focused exclusively on the "fat people are stupid" element and left all this info out. Shame on them.

Rachel said...

There are more males born in America than female, yet by age 18, the female to male ratio has surpassed the birth rate imbalance because of the kinds of activities males are more inclined to engage in. One of the most influential is car accidents, in which a disproportionate number of teenage males are killed.

So, where's the moral outrage and headlines reading "Teenage male? Drive at your own risk!"

Robert Nichols said...

Great blog, great information