The goal of evidence-based medicine (EBM) is to base medical care only on the best evidence: rigorous randomized controlled trials (RCTs). In general, this seems to make sense, but as an overarching objective applied to all cases, it can become absurd.
It’s been 15 years since BMJ published the most rigorous type of study there is — a systematic review of randomized controlled trials — to assess the evidence for using a parachute to prevent death and major injury when jumping from a plane.
They had to conclude, “As with many interventions intended to prevent ill health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomized controlled trials.”
But at long last, an RCT on this topic exists.
The absence of randomized controlled trials for a certain medical intervention does not mean that the intervention cannot be safe and effective.
And, an RCT often would be unethical, as I noted in a past blog on the “tyranny of the RCT.” Sometimes, well-designed observational studies must suffice.
And common sense matters too. After all, if you had 100 people diagnosed with dehydration, you wouldn’t give water to only half of them and see what happens to the other half.
But what is common sense to some of us may be completely unknown to others.
For example, it’s obvious to most pain patients that more severe pain requires higher doses of opioids. The inverse is also usually true, that if people are taking high doses of opioids, it means they are in more pain (in general and when drug metabolism isn’t an issue).
Yet in opioid research, increasing doses are correlated with negative outcomes while the positive pain-relieving effects are completely ignored. Researchers design and report their studies as though the doses of opioids taken were “independent variables” and not correlated with anything significant, like pain.
This is making the current glut of opioid research mostly useless and even deceptive because it doesn’t control for (or even mention) the level of pain that is relieved by opioids.
It’s like running a study to find adverse effects of blood-thinners and, like with opioids, report only on negative outcomes like fatigue and dizziness (common side effects of these medications) without mentioning that
When medication doses are studied without taking into consideration what the medication is being used for, the results become nonsensical.
If blood-thinners or other critically necessary drugs were studied and condemned for their side effects like opioids are, no one would take any medications at all.
The authors then poked fun at evidence-based medicine advocates who “have criticized the adoption of interventions evaluated by using only observational data” with a recommendation:
“We think that everyone might benefit if the most radical protagonists of evidence-based medicine organized and participated in a double-blind, randomized, placebo-controlled, crossover trial of the parachute.”
(Note: A crossover trial means every participant will eventually jump from the plane without a parachute.)
Ah, but the method of madness matters!
- The non-participating passengers flew at 800 km/hr at an altitude of 9,146 m, but
- the trial participants jumped a whopping 0.6 meter (2 feet) from a plane traveling at an incredible 0 km/hr.
The authors point out their trial’s glaring limitation — an inability to generalize to higher altitude jumps — and use it make a point that health journalists would be wise to remember:
“When beliefs regarding the effectiveness of an intervention exist in the community, randomized trials might selectively enroll individuals with a lower perceived likelihood of benefit, thus diminishing the applicability of the results to clinical practice.”
Put plainly, if most people already think an intervention works, then an RCT may end up with enough bias in its design that the conclusion ends up clinically meaningless.
I’ve been complaining about this for a long time: Opioids Blamed for Consequences of Chronic Pain
Author: Tara Haelle (@TaraHaelle) is AHCJ’s medical studies core topic leader, guiding journalists through the jargon-filled shorthand of science and research and enabling them to translate the evidence into accurate information.