I find that news releases on health research often do a lousy job of communicating what the findings actually are, and how they might inform people’s decisions. Often, in order to make sense of them at all, you have to know some statistics, read between the lines, and cut through the hype. The problem seems to be especially severe in the case of a study on the scale of something impacting populations, but hyped for the public because the authors don’t trust the reader to care unless they’re scared. There’s a difference between public health and personal health, and although the two are connected, statistically, the conclusions can be wildly different depending on your point of view – managing populations, or managing your own choices. Also, when people make decisions about their own health and safety, they fall prey to some particularly nasty logical fallacies (all natural means harmless, or it’s not cancer, so it’s fine – or, “not likely to be me” means that “it won’t happen to me”). Even nastier, research on sensational subjects – like all scientific research – often turns up complicated or ambiguous results that get distilled into inaccurate clickbait. Never fear, though, let’s play pretend, and sort through, now and forever, how to think about statistics and clickbait-y health headlines. (I sourced the images in this article from Wikimedia Commons, as usual, and the attributions are at the bottom of this page, to help maintain the suspension of disbelief.)
Bacotania is an imaginary country with a rich cultural history deeply intertwined with the consumption of cured pork. The total population is about 12 million, and national holidays include February 4th, Remembrance Sausage Day, and October 16th, Bacotanian Liberation Day. The festivities of Liberation Day culminate in a Liberation Day Bonfire Feast in which chunks of pork belly are roasted on sticks over Liberation Day Bonfires in honor of the heroic air drop of canned bacon into the besieged capital city of Schlachteplatte.
Needless to say, bacon is very important to the people of Bacotania, and the loss of cured pork products would cause immense damage to the economy and culture of the country. The 2015 decision by the World Health Organization’s International Agency for Research on Cancer to classify processed meat consumption as a Group 1 Carcinogen was met with increasing public unrest, including mass demonstrations outside the Surgeon General’s office in Schlachteplatte, which led to the Surgeon General stepping down from their post.
Congratulations! YOU have just been appointed Surgeon General of Bacotania.
What is your advice, concerning the consumption of cured pork products?
You’ll need some further information:
What is a Class 1 Carcinogen? In a masterpiece of shoddy journalism, a lot of press outlets didn’t discuss what the classes even meant. The IARC classifies substances based on how conclusive the evidence is that they cause cancer at all, NOT even remotely based on how dangerous they are. There’s only one item in Group 4, the Probably Does NOT Cause Cancer group, and that’s Caprolactam. I’d never heard of caprolactam before doing the research for this post. It’s used in nylon manufacture, and it’s definitely not harmless, but we’re pretty sure it doesn’t cause cancer. Nobody seems to have studied whether, say, pure water causes cancer.
What is an individual’s chances of getting cancer from bacon? The average lifetime chance of getting colon cancer is about 4%. According to the World Health Organization, the chance of getting colon cancer rises by 18% for every 50 grams of processed meat consumed per day. Now, we need one more bit of information, and that is the average consumption of processed meats. According to this study, average daily consumption of meat (all types) was 128 grams per day, and 22% of that was processed meat. So (22% of 128 grams gives you how many grams are processed meat) that means that the average person eats 28.16 grams of processed meat per day. So, if you start at 4% with 28.16 grams, and add 18% of 4% for every 50 grams eaten over the 28.16 gram starting point, you end up with an average Bacotanian’s cancer risk.
How much bacon does the average Bacotanian citizen eat? Bacotanians are very fond of processed meat, and a traditional Bacotanian Breakfast involves lots of sausage, so they eat twice the processed meat that Americans do, at 56.32 grams per day.
What is the average Bacotanian’s cancer risk then? Well, we need to figure out how much more processed meat than the American average an average Bacotanian eats, and then figure out what proportion of 50 grams it is, and then add that proportion of the 18% of 4% to the average 4%. Got it? Let’s go!
56.32 – 28.16 = 28.16, because it’s twice, remember? Easy!
28.16 extra grams eaten divided by 50 (grams to raise risk by 18% of 4%) = 0.5632 (amount of the 18% excess risk we should add)
0.5632 of 18% = 10.1376% Cool. Now we’re getting somewhere.
10.1376% of 4% = about 0.004, which is 0.4%
So, the average Bacotanian faces an elevated lifetime colorectal cancer risk of 4.4% on account of their huge processed meat habit. This means that for the average bacotanian, their MORTALITY ROULETTE WHEEL lands on DEATH BY BACON not much more often at all compared to the American population. (Bacotanian healthcare and mortality from colorectal cancer are comparable to ours.)
How many excess colorectal cancer cases are likely to occur in Bacotania if people continue to eat processed meat at this pace? Well, 0.4% of the total population are going to lose that roulette round, so…
0.04% of 12 million is… 48,000. YIKES! That means that Forty-eight THOUSAND Bacotanians are going to get cancer from bacon, above and beyond even the background colorectal cancer rates. If you factor that in, it’s a staggering 528,000 cancer cases. The cost to society, and the personal emotional toll on all those families is absolutely astronomical. And, clearly, partially preventable.
So, that’s how the same decision – eat the bacon, tell people not to eat bacon – ends up looking very different from the perspectives of an individual Bacotanian and the Surgeon General of Bacotania. The Bacotanian might well accept the risk, shrug, and tuck into a full Bacotanian breakfast of smoked sausages anyway. Note that although it’s a Class 1 Carcinogen, processed meat has a much smaller chance to cause cancer, compared to other Class 1 Carcinogens, like Asbestos, which (depending on your own exposure) can have lifetime risk rates as high as a 25% if you were a construction carpenter in the United Kingdom for a couple decades before 1980. Also, note that this only concerns cancer risk, not whether the cancer has a high mortality rate, and not concerning other health risks associated with the substance. (Remember that although Caprolactam is the sole occupant of Probably Does Not Cause Cancer Group 4, it’ll still cause your skin to slough off. Nice.)
So, maybe suggest that Bacotanians cut back on processed meats, but that the Bacotanian Liberation Day Bonfires likely won’t do you any harm.
Probably want to suggest the closure of Ye Wooly Salamander Particle Board Mill, though…
- Vintage Photo, United States of America. No, I have no idea what’s going on here. By UW Digital Collections [No restrictions], via Wikimedia Commons
- British Ration Can of Bacon from WW II. Seriously, my heaviest of two cats weighs 12 lbs. That’s a LOT of 70 year old bacon. By KingaNBM [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons
- Hungarian Szalonnasütés By Christo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons