Although death certificates in the United States do not include medical error as a potential cause of death, we know it happens. Martin Makary and Michael Daniel at Johns Hopkins University School of Medicine in Baltimore have put a number on it. Using historical studies starting in 1999 and extrapolations based on hospital admissions in 2013, they estimate that as many as 400,000 U.S. patients die annually because of medical error, making it the third leading cause of death in the United States, after heart disease and cancer. Their analysis was published yesterday in the BMJ.

Death certification in the United States relies on assigning an International Classification of Disease (ICD) code to the cause of death. Causes of death not associated with an ICD code, such as human and system factors, are not captured.

Despite the absence of accurate data, Makary and Daniel note that recent estimates suggest a range of 210,000 to 400,000 deaths a year among U.S. hospital patients. They calculated a mean rate of death from medical error of 251,454 a year.

Makary and Daniel compared their estimate to the annual list of the most common causes of death in the United States, compiled by the Centers for Disease Control and Prevention, which led them to rank medical error as the third most common cause of death in the United States.

They acknowledge that human error is inevitable, but say “although we cannot eliminate human error, we can better measure the problem to design safer systems mitigating its frequency, visibility, and consequences.”

They believe strategies to reduce death from medical care should include three steps: Making errors more visible when they occur so their effects can be intercepted; having remedies at hand to rescue patients; and making errors less frequent by following principles that take human limitations into account.

The last point brought to mind a recent conversation I had with Bryce Rutter, founder and CEO of Metaphase Design Group (St. Louis, MO), who is a leading specialist in handheld product design. He is passionate about “taming the technology” in healthcare products.

“I’m amazed by how many fascinating products with exceptional technology get to market where the human factors are so poorly articulated and resolved that the user—be it a surgeon, nurse, anesthesiologist or whomever—has great difficulty accessing the full potency of the technology,” Rutter told me. In fact, runaway feature creep in medical device design has the potential to “create noise and confusion, says Rutter, who recounted his work on the da Vinci surgical robots as an example.

“The surgeon only has so much cognitive bandwidth,” explains Rutter. “If part of that bandwidth is consumed by doing realtime computations of behavioral control outputs to compensate for poor design, those cognitive resources are unavailable to the surgeon, who needs to focus on the surgical procedure itself.”

We will never completely eliminate human error, of course, but we should not enable it through poor product design. In a healthcare setting, that should be a given.