Study: medical errors are the third biggest cause of death in America

Medical errors kill more people than car crashes or new disease outbreaks. They kill more people annually than breast cancer, AIDS, plane crashes, or drug overdoses. A new study estimates that they are the third leading cause of death in the United States, causing a quarter-million fatalities in 2013 alone.

Patient safety researchers Marty Makary and Michael Daniel published new data in the British Medical Journal Tuesday suggesting that preventable medical errors resulted in 251,454 deaths in 2013. If that estimate is correct, the only bigger causes of death are heart disease and cancer.

The researchers worry, however, that their number is actually an underestimate — that medical harm kills even more patients than we're currently able to count.

"Something like 2 to 3 percent of people who go into the hospital are going to have some pretty severe harm as a result," Don Berwick, the Obama administration's former Medicare administrator, previously told Vox. "Australian studies show that the rate might be as high as 12 percent. The harder you look, and the more you study the issue, the more errors you find."

It's incredibly difficult to know how many deaths result from medical harm

When there is a plane crash in the United States, federal law requires airlines to report that information to the National Transportation Safety Board. It investigates each incident and tries to figure out what went wrong and how it could be prevented in the future.

But there's no analogous body in health care.

When a patient dies as a result of medical harm, there's no regulator that has to get notified — the hospital doesn't send off paperwork about the error that occurred. Sometimes the information gets jotted down in the patient's medical record, but even that is not a certainty.

This makes estimating the frequency of medical harm very difficult — and researchers generally believe that their figures underestimate the prevalence of harm. Their study uses data from four recent studies, all of which relied on medical records to estimate fatalities caused by medical errors. So the authors know that their estimate of fatalities misses any errors that weren't captured in the medical record.

"We believe [our estimate] understates the true incidence of death due to medical error because the studies cited rely on errors extractable in documented health records and include only inpatient deaths," Makary and Daniel write.

Still, they argue that there is value to putting out the best number they can find, as it can draw attention to the potential magnitude of a rarely discussed problem in health care.

"The absence of national data highlights the need for systematic measurement of the problem," they write.

The most common errors seem mundane and boring. But they can be very deadly too.

Some errors in medicine are stunningly bad. One study, published in the journal Surgery, found that surgeons operated on the wrong part of the body 2,413 times between 1990 and 2010. They left foreign objects behind in the body (typically sponges) 4,857 times. In 27 cases, they operated on the wrong patient altogether.

These errors are terrible and easy to recognize. But they aren't what cause the most harm in American health care. It's the less stunning, more quotidian mistakes that are the biggest killers. Take, for example, bed sores.

Bed sores are one of the more mundane complications of modern medicine. They're called "pressure ulcers" in medical jargon, and are the open wounds that patients develop when they have not moved for long periods of time. The skin literally cracks under the pressure of the body weighing down on it.

A 2006 government survey found that more than half a million Americans are hospitalized annually for bed sores that are the result of other care they have received. And 58,000 of those patients die in the hospital during that admission.

Does this mean that pressure ulcers killed all those patients? No — these are typically frail, elderly patients battling other conditions ranging from pneumonia to dementia. But did bed sores mean some of these patients died who otherwise wouldn't have? Experts say that's almost certainly the case.

The fact that pressure ulcers persist as a problem in health care is revealing. It shows that even when we know the root cause of medical harm, finding a fix can prove difficult. The logistics of preventing bed sores, for example, are known but cumbersome, requiring the constant turning and movement of immobile patients.

"This requires people to adhere to a really strict schedule of checking the patient, often in nursing homes that are poorly staffed," says Lucian Leape, a patient safety expert at Harvard University. "It's really all about providing rigorous attention, and that doesn't always happen."

Learn more about medical errors from Vox's series Fatal Harm

Medical errors are ubiquitous to the American health care system, and I spent much of the past year understanding how and why medicine goes wrong. You can read a larger explainer of why medical harm is so prevalent — and the most common types of mistakes — here.

The series includes the story of a young girl who died just short of her fourth birthday after experiencing numerous preventable infections. And it profiles a nurse whose error caused the death of a young infant — and who killed herself seven months later. See the full series here.