Women 65 and older are five times more likely to die in the first year following a hip fracture than non-injured women in the same age group, according to a new study funded by Kaiser Permanente Northwest.

The new study is the first to suggest “a possible cause-and-effect relationship” between hip fracture and death, said Kaiser researcher Erin LeBlanc.

“Before we might have assumed that sicker women are just more likely to get hip fractures,” Dr. LeBlanc said. “But now we know that there is something about the hip fracture itself, and not an underlying condition, that is bringing on this increased risk of death.”

LeBlanc said the top three causes of death – heart disease, stroke, and sepsis – were the same for both the fracture and control groups in the study, which followed more than 1,000 women in four states over 19 years. But she said more than half the deaths in the fracture group occurred within three months of injury, and nearly three-quarters occurred within six months.

“This suggests that something about the surgery, hospital time, immobility, or rehabilitation required after a hip fracture makes women more vulnerable,” LeBlanc told CNN Health.