Mend Physical Therapy Blog and Injury Information

WWII, Survivor Bias, And Why Some PTs Continue With Ineffective Treatments

March 17, 2020


Prior to World War II, mathematicians were not included as members of the US military, but this is not to say mathematics was not utilized. At the beginning of the war German air defenses were effective at downing our aircraft and those that returned often were riddled with bullet holes. Planes showed patterns of bullet holes along their wings and fuselage leading some military leaders to question if more armor should be placed in these areas to make planes safer. Mathematicians were quickly consulted on how additional armor could be placed in all areas except the relatively untouched cockpits and engines without sacrificing flight performance. Mathematicians quickly realized the bias of this thinking by only considering which planes returned safely not the ones who were shot and downed or downed due to mechanical failures. As the story goes, considering all the planes and not only the ones that returned safely allowed engineers to place armor strategically in the key areas of the engine and cockpits to allow.

Utilizing only available information and not the complete data set has flawed numerous professions and can also be seen in healthcare. Providers, including Physical Therapists, can show remarkable levels of bias in the delivery of treatments they are convinced help with a given condition. Even in the face of research studies questioning their use, clinicians will often state the benefits heard from their returning patients. Similar to the WWII story above these clinicians are demonstrating survivorship or survivor bias and fall victim to the errors of an incomplete or small sample size. By ignoring the patients who did not get better or did not return to clinic they are susceptible to bias which perpetuates the delivery of these ineffective treatments. Example, John Smith did not return after his first treatment so he must be cured.

To improve our delivery of healthcare services we must aim to reduce ineffective treatments which only lead to greater degrees of unwanted practice variation and prolonged patient recoveries.