Voices From The Community
A matter of risk
Story by Connie Bryson/Illustration by Sarah Clement
An expert in medical genetics explains how we can use information about risk reduction to make important health decisions and reduce our disease risk.
Health news is a staple of today’s media. You can’t read a newspaper or watch television without finding out about the latest study suggesting that, if you take medicine or supplement X, you will reduce your risk of getting disease Y. If these treatments worked as reported, surely we’d be disease free by now.
But we’re not—and one reason that treatments often seem more beneficial than they actually are is because benefits are presented as reductions in relative risk as opposed to reductions in absolute risk. The way risk results are reported makes a big difference, and it’s a pet peeve of Dr. Jim Evans, a clinical professor at the University of North Carolina School of Medicine. He was in Alberta in March to give the 2011 Picard Lecture at the University of Alberta’s Health Law Institute.
“When you are thinking about what treatment to choose, or whether to opt for treatment at all, what really matters is absolute risk, not relative risk,” says Dr. Evans. “Everyone—patients and doctors—should pay attention to this.”
Relative risk compares the risk in two different groups of people. It could be smokers versus non-smokers or women who take a certain treatment for breast cancer versus women who take a different treatment.
Absolute risk refers to your specific risk of developing the disease over a time period. We all have absolute risks of developing various diseases such as heart disease, cancer, and stroke. Doing something that is preventative or protective, such as take a certain drug or exercise, may reduce your absolute risk.
What bothers Dr. Evans is the use of relative risk reduction when talking about common diseases for which we have a high absolute risk. For example, a 70-year-old man gets his cholesterol checked, and it’s a little high. His doctor is thinking of putting him on lipid-lowering medication and tells him it will reduce his relative risk of heart disease by 25% over the next 10 years.
“Yes, this sounds good, but in fact relative risk is useless information on its own,” says Dr. Evans. “What the patient really needs to know is his absolute risk of heart disease now and what his absolute risk will be after taking this medication. Relative risk only makes sense in the context of absolute risk.”
In this example, the absolute risk of this patient developing heart disease in the next 10 years is 55%. If he takes the medication, his absolute risk of getting heart disease will be 41%. In other words, the patient’s absolute risk of developing heart disease after taking medication was reduced only by 14%—less than his relative risk reduction which was 25% over the next 10 years. “While there has been substantial relative risk reduction, it’s important to understand that this patient’s absolute risk is still very high,” notes Dr. Evans. “Focusing on relative risk reduction can give you a false sense of security about your risk or, conversely, a sense of doom. My advice is to find a healthcare provider who can help you put claims into perspective.”
When his patients ask him about things like taking selenium to prevent cancer or taking up crossword puzzles to ward off dementia, Dr. Evans suggests that they keep their eye on the right target and points to five actions that will go the farthest to ensuring a long and healthy life:
- Exercise
- Eat a reasonable diet and a moderate amount of food
- Do not use tobacco products
- Drink responsibly and never drink and drive
- Wear your seat belt
“The reality is if you take care of these five things, you will be taking care of 90% of the things under your control,” says Dr. Evans. “The rest is just tweaking your absolute risk.”