Sepsis, a life-threatening response to infection, is a common cause of deaths in hospitals, according to a new report.

The study looked at 568 people who had died in hospitals and whose average age was 70. More than half had sepsis, and it was the immediate cause of death for nearly 200 of them; another 100 had sepsis but didn’t die of it. Only 36 of the sepsis deaths might have been prevented with earlier antibiotic treatment or other measures, the researchers determined.

Dr. Chanu Rhee, an infectious disease and critical care physician at Brigham and Women’s Hospital and the study’s lead author, said that many hospital patients with sepsis are elderly, frail, suffering from multiple underlying diseases and often terminally ill, and they do not survive even when provided with timely and appropriate care.

“Any preventable death from sepsis is a tragedy,” Dr. Rhee said, “but there is a perception that all sepsis deaths are preventable, and this study challenges that perception.” The study was published in JAMA Network Open.