Astronauts who spend more than 90 days in space face a higher risk of hip fractures later in life, a new study has found.

Researchers surveyed 379 US astronauts about fractures reported in annual check-ups. Using statistical modelling, they found hip fractures were more common after long missions.

The breaks also came at younger ages than hip fractures usually occur on Earth. Only six hip fractures turned up in the whole group, so the numbers are small.

"Spaceflight-induced bone loss can lead to real long-term fracture consequences," said co-author Moshe Gertzulin of the Hospital for Special Surgery in New York.

Weightlessness is known to weaken bones. The finding adds to the case for better countermeasures, from exercise to artificial gravity, on long interplanetary voyages.

Better countermeasures will matter for long interplanetary voyages. The researchers used Bayesian modelling to draw conclusions from the small astronaut sample. The work was led by researchers at Baylor College of Medicine.