There are three kinds of lies: lies, damned lies, and statistics. – Benjamin Disraeli, British Politician, (1804-1881)
Have you ever been completely overwhelmed while reading the morning paper? 1 in 6 American men will be diagnosed with prostate cancer during his lifetime (American Cancer Society, October 2008). Studies estimate that CT scans account for as much as 2 percent of all cancers (as reported by Reuters, December 2008). People who sleep less than seven hours a night are three times more likely to develop a cold than people who sleep eight hours or more a night (Carnegie Mellon University, January 2009). Mouthwash linked with increased cancer risk (Australian Dental Journal, January 2009). How are we to interpret and digest all of this information? Data about relative risks and absolute risks – heck, it’s 6:30 a.m. and I’m lucky if I can focus long enough to read the back of the Wheaties box.
According to a January 11, 2009 article in the Sacramento Bee, ‘Risk percentages, drug benefit numbers and survival rates can be manipulated as deftly as a chiropractor cracking a back.’ An article published the same day in the Chicago Tribune cited a group of physicians at Dartmouth Medical School as saying that ‘taking time to understand the often-confusing statistics used in the medical industry, is key to making smarter decisions about your individual healthcare.’
Here are some tips to remember when wading through the 11 o’clock news:
· Differentiate between a lifetime risk and an annual risk. An annual risk is the number diagnosed each year in a population, usually expressed as a number per 1,000 or 100,000 individuals in the population. The lifetime risk is the sum of the risk of developing that disease each year, and thus sounds far more ominous.
· Where possible, re-frame the statistic. Yes, colon cancer strikes 150,000 Americans, but there are 300 million Americans, which means you only really have a 0.05 percent chance. Don’t you feel better already?
· Know your starting risk. If a drug company says their drug will result in 50% fewer deaths, then you need to ask: what was the starting risk of death? As the Chicago Tribune article so beautifully analogized: a 50% off coupon applied to a 50-cent pack of gum reaps different savings than when applied to a $35 turkey. So did you start with the gum or the turkey?
· Check to see if the study involved people similar to you in terms of age, gender, risk factors and family history. While you’re at it, double check to make sure the study referenced human subjects, as opposed to rodents.
Above all, remember that getting a disease does not, by a long shot, mean dying of it.
Intrigued? Try perusing “Know Your Chances: Understanding Health Statistics”, S. Woloshin, L.M. Schwartz, and H.G. Welch, University of California Press, November 2008. My favourite: “Struck By Lightning: The Curious World of Probabilities”, J.S. Rosenthal, HarperCollins Canada, September 2005.
Jennifer Hartman, Guest Blogger