Statistics, the language of medical researchers, can be a source of great confusion for the average health consumer. I encourage women to look beyond the sensationalist headlines and arm themselves with the real facts. Knowledge that encourages you to be proactive and take responsibility for your health is empowering and will greatly enhance your overall state of health. Your physician is there to help you but it’s YOUR body and you need to be part of the team!Let me give you some background for the chocolate headline that caught your attention. For example, let’s say that 3% of the people who eat chocolates develop cavities, and 2% of people who do not eat chocolates develop cavities. The difference between these populations is only 1%. In terms of absolute risk, that means that for every 100 people who eat chocolates, 1 extra person will develop cavities (in addition to the 2 who will develop cavities without eating a single truffle).
This is not a particularly frightening risk if you enjoy chocolate because 97 out of 100 who eat chocolate will not get cavities! But suppose we report the identical conclusion as a relative risk, a statistical term that compares the risk of a certain disease in two different groups. The group who doesn’t eat chocolate is given a risk of 1.00, while the group eating chocolate is given a risk of 1.50 because they get TWICE as many cavities. When people hear the risk of cavities from eating chocolate is increased by 50%, they may mistakenly assume that 50 of 100 eatingchocolate get cavities! On the contrary, it’s a very acceptable risk when you know that the absolute risk is only one more person who will get cavities!
Let’s use your new understanding of statistics to explain women’s concerns about hormone replacement therapy (HRT) and breast cancer. Many of the studies of HRT and breast cancer, have produced statistically modest or borderline results that have been made to look more impressive than they actually are by reporting them as relative risks.
The following slide on “Relative Risks for Breast Cancer” lists the reported increases in relative risks associated not only with HRT and ERT (estrogen alone) but also with birth weight, fish intake, eating 1 additional serving of French fries per week during preschool years, eating grapefruit, working on a night shift, working as an airline fight attendant in 2 different airlines, suffering from severe caloric restriction during the 1944-1945 Dutch famine, taking antibiotics and the use of electric blankets by African-American women. (Yes, there were actual studies reporting all these different findings!)
The relative risks in almost all cases are very low and the use of HRT is virtually the lowest, being less risky than eating fish or grapefruit, using antibiotics or being a flight attendant! To put the relative risks in perspective, the relative risk for smoking and lung cancer is 26.07! That’s something people can relate to that is an irrefutable risk of which most people are aware.
Marina Johnson, M.D., F.A.C.E.