COGNITIVE INERTIA AND TECHNOLOGICAL ABANDONMENT IN MEDICINE

Purpose: Randomized trials often find that costly, widely-used medical technologies are not effective. These trials may reduce costs, but only if physicians modify their beliefs accordingly. Since 1984, a number of studies have found that routine episiotomy during vaginal delivery does not benefit mothers or babies. We document “cognitive inertia” – the persistence of beliefs in the face of contradictory evidence – in physicians' use of episiotomy.

Methods: We measure physician-level episiotomy rates using Pennsylvania Inpatient Hospital Discharge Data for the period 1994 to 2010. The data are a census of hospital discharges in the state. The data include physician identifiers that can be linked across years. We identified spontaneous vaginal deliveries and episiotomy using ICD-9 diagnosis and procedure

Results: The sample includes over 1.6 million non-operative vaginal deliveries. The episiotomy rate decreased from 42% in 1994 to 10% in 2010. The figure shows trends in episiotomy rates by the year in which physicians entered practice. For example, the top line shows rates among physicians who entered practice before 1994. The next line shows rates among physicians who entered between 1995 and 1998. Older physicians reduced their use of episiotomy but continued to perform episiotomy at much higher rates than younger physicians. For example, in 2010 the episiotomy rate was 13% among physicians who entered practice before 1994. The episiotomy rate was only 5% among physicians who entered practice in 2009-2010.

Conclusion: Even as late as 2010, a woman treated by an older physician was substantially more likely to receive an episiotomy. We find that there is a clinically-significant degree of inertia in physicians' practice patterns in this context. There are no learning or switching costs that would have made it more difficult for older physicians to discontinue routine episiotomy, indicating that observed patterns are attributable to cognitive inertia. Results suggest caution in permitting technologies to diffuse into routine practice before they have been tested in trials.