Study Design Red Flag 🚩: All-Cause Mortality
If there’s a research term that I often put a red flag on the results, it’s “all-cause mortality.” It’s a red flag for me because the manufacturers/researchers are often concluding that intervention XYZ works because it decreases all-cause mortality (i.e., your chance of death). It’s often a pharmaceutical intervention, like the flu shot, boasting that there’s a decrease in death among the people who get the shot.
If an intervention is created to prevent a specific outcome, then it should only be allowed to use that specific outcome as a sign of effectiveness. Using all-cause mortality is using death statistics from any possible way you can die: car accidents, Central Park stabbings, bathtub drownings, smoking, and even the 3rd leading cause of death, our US health care system.
It’s like a commercial saying, “This new drug for blood pressure is so effective that you, as the parent taking it, will decrease your child’s risk of death from SIDS.”
Along with the “all-cause mortality” outcome, there’s often a term called “frailty-selection bias.” They don’t count the frail people who are most likely to die.
They claim their intervention decreases death by any cause except for the people who are most likely to die during their data collection, so we’re not going to count them.