Understanding Risk: Absolute Risk vs Relative Risk
It’s Sunday morning and you are in the kitchen making coffee, trying to watch last night’s monologue from your favorite late night comedian on YouTube. Suddenly your comedic interlude is rudely interrupted by an advertisement featuring an ethnically balanced assortment of older people. They look like the models from a United Colors of Benetton ad, forty years later and seem unusually active for their age. A soothing voice begins asking you very personal questions:
Are you experiencing forgetfulness, urinary incontinence, jumpy legs, racing thoughts, road rage, difficulty locating your keys?
“Yes,” you say to the old people on the screen who are now riding ferris wheels and swinging toddlers around in circles. Then comes the kicker:
Lobotomy-ovasin can reduce your risk of cranial senescence by 50%. Ask your doctor if lobotomy-ovasin is right for you.
Wait, did you hear that correctly? A 50% reduction in cranial what? If you don’t get on this drug ASAP, do you have a 50% risk of losing your mind? How did they come up with that number?
Risk nomenclature is a powerful marketing tool. An effective way to move product is to scare people into believing they are going to die without said product. This is why you need to understand the difference between relative risk and absolute risk, because they are quite different. What you want to know is your absolute risk of dying prematurely both with and without this drug.
Take, for example, the above hypothetical disease, “cranial senescence.” Let’s imagine that your chances of dying prematurely from cranial senescence is 0.2% and taking lobotomy-ovasin reduces that chance of early death to 0.1%. Your relative risk of dying has been reduced by 50%, yet your absolute risk of dying has only been reduced by 1/10 of a percent. Stated simply:
If you don’t take lobotomy-ovasin, your risk of early death from cranial senescence is 0.2%.
If you take lobotomy-ovasin, your risk of early death is reduced to 0.1%
That is wildly different than hearing 50% and not nearly as convincing.
Drug companies often report clinical trial findings as relative risk in effort to generate public demand and enthusiasm from study sponsors. A fine example of this is the ubiquitous use of statin drugs for lowering LDL cholesterol. In a 2022 landmark systematic review and meta analysis evaluating relative and absolute risk in statin therapy, Byrne, et al concluded that the benefits of statin therapy was modest at best. The makers of the statin Crestor presented data from a clinical trial in relative risk terms and boasted a 54% reduced rate of fatal heart attack by taking their drug. Fatal heart attacks occurred in 0.76% of the placebo group and in 0.35% of the statin treated group. In absolute risk terms the reduced rate of fatal heart attack from statin therapy is actually just 0.41%. (Byrne, et al, 2022). However, 0.41 is 54% of 0.76%, therefore, the statin makers were able to generate “unbridled enthusiasm by experts in the field” (Diamond & Leaverton, 2023).
Misunderstanding relative vs absolute risk also can impede people from receiving drug therapies they could benefit from or that may even save their lives. A famous example is the wildly misunderstood risks of menopause hormone replacement therapy (HRT). In the 1990’s an enormous study called the Women’s Health Initiative (WHI) explored HRT’s effects on women’s cardiovascular health in post menopausal women. Abruptly in 2002, the study was prematurely halted when its findings on breast cancer risk were misinterpreted and leaked to the media. The breast cancer risk, reported in relative risk, not absolute, was way overstated, and did not account for many confounding factors such as the age of the participants, and flaws in the study.
In reality, HRT is best initiated early at the onset of menopause and for most patients, is life enhancing and protective of multiple systems of the body (Hodis & Mack, 2022). The absolute breast cancer risk for a woman age 50-60 taking HRT (much younger than the WHI subjects) was actually 0.12% but the sensationalized media reported it as much higher. Hysteria from both patients and doctors ensued, doctors stopped offering HRT, treatment dropped by 80%, and an entire generation of women entering menopause lost the wide reaching benefits of this therapy (Vogel, 2017).
Decisions we make about our health should be based on facts, not fear. Be certain your provider is staying current on the latest research with any treatments they are either recommending or dissuading you from taking. Do not rely on pharmaceutical companies to make important healthcare decisions for you. Understanding risk is important when you are making a decision to take or not to take a medication or to have or not have a procedure. The more informed you are, the better equipped you will be to make decisions that are right for you and your body.
References:
Byrne, P., Demasi, M., Jones, M., Smith, S. M., O'Brien, K. K., & DuBroff, R. (2022).Evaluating the Association Between Low-Density Lipoprotein Cholesterol Reduction and Relative and Absolute Effects of Statin Treatment: A Systematic Review and Meta-analysis. JAMA internal medicine, 182(5), 474–481. https://doi.org/10.1001/jamainternmed.2022.0134
Diamond, D. M., & Leaverton, P. E. (2023). Historical Review of the Use of Relative Risk Statistics in the Portrayal of the Purported Hazards of High LDL Cholesterol and the Benefits of Lipid-Lowering Therapy. Cureus, 15(5), e38391. https://doi.org/10.7759/cureus.38391
Hodis, H. N., & Mack, W. J. (2022). Menopausal Hormone Replacement Therapy and Reduction of All-Cause Mortality and Cardiovascular Disease: It Is About Time and Timing. Cancer journal (Sudbury, Mass.), 28(3), 208–223. https://doi.org/10.1097/PPO.0000000000000591
Vogel L. (2017). Trial overstated HRT risk for younger women. CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne, 189(17), E648–E649. https://doi.org/10.1503/cmaj.1095421