If you’ve spent five minutes paying attention to medical news, you’ve undoubtedly seen the headlines: “People who take statins have 30% fewer heart attacks!” or “Breast cancer screening makes women live longer!” or “Menopausal Hormone therapy lowers Alzheimer’s risk.”
These all sound wonderful, don’t they? Just swallow a daily pill, or submit to regular screening, and you’ll join the ranks of the immortal. Were only life so simple.
Yet before you rush off to demand a prescription, let me introduce you to one of the sneakiest, most persistent mirages from the world of medical research, which we call the “Healthy User Bias.”
Readers of Brownstone were recently introduced to this concept related to the Covid vaccines in an article entitled “A Hall of Mirrors of the Healthy Vaccinee Effect,” which demonstrated that those who were vaccinated were not the same as those who weren’t. Very frail people and those close to death were less likely to get vaccinated, which is understandable, and so those who didn’t get the jab died at a higher rate than those that did. Simple, right?
Understanding this single concept may not, overnight, elevate your medical BS detector from “gullible consumer” to “battle-tested skeptic,” but to be fair, it might help.
The Kale-Eating, 6 AM Jogger Effect, and the Placebo Effect
What is the Healthy User Bias? It’s embarrassingly simple. In observational studies—where researchers merely watch what people do in the real world rather than running an experiment—the people who voluntarily take preventive drugs or pop daily supplements are fundamentally different from those who don’t. No surprise there, right?
On average, “healthy users” are wealthier, better educated, and more health-obsessed. They are seriously more obedient when it comes to vaccines (including the Covid vaccine). These sorts of people want to do the best they can within their powers, which includes things that involve some friction: they eat organic kale, jog at dawn, wear seatbelts, don’t smoke, and visit their doctors regularly. They love tests of all kinds.
A 2006 meta-analysis quantified the healthy user effect (which they called the healthy adherer effect) across 21 studies. What they found is mind-blowing in its implications. It found that those who religiously took their prescribed pills (which we call ‘good adherence’), even if it was a placebo, showed a 44% reduction in mortality (which was identical to adherence to proven beneficial therapy). All this shows is that the obedient, healthy people are more likely to do what most physicians want: they take their medication as ordered by their doctors.
When researchers observe people over ten years and notice they have fewer heart attacks and fewer strokes the light goes on. Hey, they might live longer! This is where pharmaceutical cheerleaders jump up and down, declaring: “Look! It was our pill!”
No. Sorry, it most likely wasn’t the pill. It was the person who took the pill. It was the fact that the patient was already doing 27 zillion other things to stay healthy. Maybe they had a gene that said: don’t do stuff to excess that are known to be bad for you (ie: smoking, drinking, committing violent crimes, extreme sports, being grossly overweight, being a couch potato, etc)
The pill was just along for the ride. Observational research routinely mistakes a healthy lifestyle for pharmaceutical magic.
By now you’re saying, Okay Mr. Alansmartypants, gimme some examples.
