A twitter headline from UK paper The Independent caught my eye. “Breastfeeding ‘can cut cancer by up to one fifth.'”
I tried to tweet back 140 characters about assessing risk but like most topics in life, it’s much too complicated for such a limited platform.
This is the part where the writer tries to explain statistics.
There are two different ways to look at risk. Absolute Risk is the chance of something happening without considering any intervening factors. Relative Risk is how different factors influence the absolute risk.
Example (and I’m making these numbers up). If you drive 20 miles today, you have a 15% chance of having a car accident. However, if you drive a black car, that increases your risk 10%. At first glance, you might think that your chance of having an accident in a black car is 25%.
A 10% increase of a 15% absolute risk means this. .15 * .10 = .015 Therefore, your absolute risk has increased from 15% to 15%+1.5% or 16.5%.
How that applies to the breast cancer
I’ve discussed the wizardry involved in the oft-quoted 1 in 8 statistic. It doesn’t mean that any one group of eight people, one will have breast cancer. It means that if you live to age 95, you have a 12.5% lifetime risk of getting breast cancer. Most of that risk is loaded in later years.
But just for kicks here, let’s go with 12.5%. That’s 1 in 8 expressed as a percentage. This article says that breastfeeding for 12 weeks may reduce your risk 10%-20%. There is no indication of how long that protection lasts. But again, for giggles, let’s go with the best case scenario.
12.5% risk reduced by 20% is 10%.
Of course, the context of this UK article is a national ongoing argument over breastfeeding, so instead of explaining the numbers, they are going with sensationalism to further an agenda.
I find that in non-medical outlets often the relative risk is reported on; rarely is the absolute risk mentioned. It’s much more dramatic that way.
I’m tired of people throwing around incomplete statistics in the service of an agenda. Be it the breastfeeding movement or the argument against abortion, this rotten but relatively rare disease becomes a football.
I resent that. If you want to breastfeed or not breastfeed, I think your decision would hinge on other more important factors.
Two other unintended (?) consequences of such tunnel vision agenda-pushing.
(1) It shifts the focus of blame from the disease to the woman’s choices. (If you get breast cancer, it’s because you didn’t breastfeed or you had an abortion, Therefore, you chose/deserve your disease). Yes, there are ways to reduce risk, however, the impact of those behaviors are not really clear.
(2) It masks the larger problem – that we have no idea what causes this disease and there is no cure. Simply being female and growing older far outweigh these contravening risk factors.
So please, let’s not fall for over-simplified crumbs of information. I believe that fully informed people can make decisions best for them and their own circumstances. That doesn’t make for a very catchy headline or bumper sticker though.
To borrow a concept from Jon Stewart and The Daily Show, this post has been brought you by CONTEXT.