A medical condition that often escapes public notice may be involved in 20% of deaths worldwide, according to a new study.
The disease is sepsis — sometimes called blood poisoning. It arises when the body overreacts to an infection. Blood vessels throughout the body become leaky, triggering multiple-organ failure.
It is surprisingly common in the United States: One prominent study estimates 1.7 million cases a year and 270,000 deaths. Sepsis in the U.S. can strike otherwise healthy people who get an infection that runs amok. Many other cases arise in the hospital. That occurs frequently in people who are already in poor health.
"Often the underlying cause is something like lung cancer," says Dr. Kristina Rudd, the lead author of a study published Thursday in the Lancet. Those people may develop pneumonia, which in turn leads to a deadly case of sepsis. With this domino effect, "It can be really hard to sort that out," she says. And treatment options are limited.
It's an even bigger problem in the developing world, where childbearing women are at the greatest risk. "These are women who develop an infection after they give birth or have a C-section," Rudd says. These women may develop an infection that triggers deadly sepsis, "because often they don't have access to appropriate obstetric care."
Previous studies have suggested that sepsis is at least partly responsible for 1 in 10 deaths globally. Rudd — an assistant professor of critical care medicine at the University of Pittsburgh — along with more than a dozen collaborators, including some at the University of Washington, decided to look more closely at sepsis globally.
They analyzed more than 100 million death certificates, dated between 1990 and 2007. They found that sepsis is twice as common as health officials have long believed, if not as a direct cause of death, then at least as a contributing factor.
They estimate that about 11 million people worldwide died with sepsis in 2017 alone — out of 56 million total deaths. That's about 20% of all deaths. "It's a massive number," Rudd says.
There's also good news in this study: It documents major reductions in sepsis since 1990. According to the paper, which was presented at a meeting today in Belfast, Northern Ireland, the death rate from sepsis has dropped by about half since 1990.
That's a surprising finding, says Dr. Chanu Rhee, who studies sepsis and infectious disease at Harvard Medical School. "It's really interesting that in their study, they actually found the incidence of sepsis declined over the study period," he says, "where other studies have actually suggested the opposite."
Sepsis is not easy to study, in part because doctors may not think to include it as a cause of death or as a contributing factor on a death certificate.
"The accuracy of death certificates tends to be fairly poor," Rhee says. So while he considers the new study an important contribution, he isn't taking the results literally.
Rhee has studied sepsis occurrences and deaths in the United States. His own findings here actually paint a gloomier picture than the new study does when it looks solely at U.S. death certificates. So sepsis might actually contribute to more than 20% of deaths globally, he says.
For Rudd, the decline she and her colleagues have reported since 1990 seems consistent with a worldwide effort to improve public health, including "provision of clean drinking water and sanitation infrastructure and development of vaccines and effective antibiotics," she says.
Still, there's a lot of room for improvement in those efforts — as well as a need to have more effective treatments. Better therapy may be of only short-term help to someone who is dying of lung cancer, but for millions of people around the world who get an infection during childbirth, from a hospital infection or in a vehicle accident, effective treatment of sepsis would be a true lifesaver.
You can contact NPR science correspondent Richard Harris at email@example.com.
MARY LOUISE KELLY, HOST:
Now the story of a very common but very often overlooked cause of death. A new study concludes that sepsis is involved in a surprisingly high proportion of deaths globally. The illness is essentially the body's overreaction to infection. NPR science correspondent Richard Harris reports.
RICHARD HARRIS, BYLINE: Antibiotics are wonder drugs, but even so, infections remain a very common cause of death. So, too, is sepsis or blood poisoning. Dr. Kristina Rudd at the University of Pittsburgh School of Medicine says these two related conditions are often studied separately.
KRISTINA RUDD: But I really felt like there was a lot of work to be done to put these two things together.
HARRIS: Rudd and a big team of colleagues studied 100 million death certificates collected worldwide between 1990 and 2017. They found that sepsis turns up twice as often as health officials have long assumed - if not as a direct cause of death, at least as a contributing factor.
RUDD: Approximately 11 million people worldwide every year die with sepsis.
HARRIS: So it's about 20% of global deaths.
HARRIS: That's a huge number.
RUDD: It's a massive number.
HARRIS: In places with poor medical care, child-bearing women are at greatest risk.
RUDD: These are women who develop an infection after they give birth or have a C-section or women who suffer a miscarriage and then go on to have an infection because often, they don't have access to appropriate obstetric care.
HARRIS: In this country, the cases are more varied. Sepsis can strike otherwise healthy people who get an infection that runs amok. Other cases arise in the hospital - that's often among people who are already in poor health - and it causes multiple organ failure.
RUDD: Often, that most underlying cause is something like lung cancer that then led to pneumonia that then led to sepsis, and then the person died. And so it can be really hard to sort that out.
HARRIS: Obviously, if 20% of deaths have sepsis as a component, that means there's huge room for improvement. Rudd's study does report major success since 1990. According to her paper being presented at a meeting today and being published in The Lancet, the global death rate from sepsis has dropped by 50% since 1990.
CHANU RHEE: It's really interesting that in their study, they actually found that the incidents of sepsis declined over the study period, where many other studies have actually suggested the opposite.
HARRIS: Dr. Chanu Rhee studies sepsis at Harvard Medical School. He says the new study is an important contribution, though he doesn't take the numbers literally because doctors don't report sepsis consistently. His own findings on sepsis in the United States have even scarier numbers than the new study, so this latest publication could actually be an underestimate. And Kristina Rudd says she thinks the global decline is real, driven by public health measures.
RUDD: This is provision of clean drinking water and sanitation infrastructure and development of vaccines and effective antibiotics.
HARRIS: Still, there is a lot of room for improvement in public health as well as for developing effective treatments for sepsis.
Richard Harris, NPR News.
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