Many cases of so-called crib death, about one in eight, occur among infants who have been placed on sofas, researchers reported on Monday.

Dr. Jeffrey Colvin, a pediatrician at Children’s Mercy Hospital in Kansas City, Mo., and his colleagues analyzed data on 7,934 sudden infant deaths in 24 states, comparing those that occurred on sofas with those in cribs, bassinets or beds.

Previous research had shown that couches were particularly hazardous for infants. The new analysis, published in the journal Pediatrics, tried to identify factors significant in these deaths.

“It’s not only one risk that’s higher relative to other sleep environments,” said Barbara Ostfeld, a professor of pediatrics at Rutgers Robert Wood Johnson Medical School who was not involved in the new study. “It’s multiple risks.”