In Peter Attia’s bestseller, Outlive, he tells a story that illustrates a common (and costly) decision error we make in interpreting data about relative risk.
Prior to 2002, hormone replacement therapy (HRT) was a standard treatment for adverse symptoms in menopausal women. In 2002, all of that changed with the publication of results from the Women’s Health Initiative Study (WHI) which reported a 24% increase in the risk of breast cancer among a subset of women taking HRT. As Attia points out, these results generated a massive media response, with a flurry of “headlines all over the world [that] condemned HRT as a dangerous, cancer-causing therapy.”
The study changed the way that people going through menopause and experiencing adverse symptoms were treated. Given that the decision decision about whether to take exogenous hormones during menopause comes down to an assessment of the trade-off between the symptoms of menopause HRT was designed to treat and the downside risks of that treatment, the 2002 study seemed to really change that calculus. As Attia put it, HRT became “virtually taboo.” And it’s easy to understand why. Who would want HRT, and what doctor would recommend it to a patient, if it meant such a big increase in the risk of breast cancer?
But this response is an error of interpretation, mainly because it doesn’t take into account the underlying absolute risk of breast cancer.