A large, nationwide study of children who suffer cardiac arrest while in the hospital has revealed an under-recognized and potentially preventable problem.

Hospitalized children who have a cardiac arrest and are resuscitated by hospital staff between 11 p.m. and 6:59 a.m. are less likely to survive to the time of discharge than children who have a cardiac arrest between 7 a.m. to 10:59 p.m., according to a study published Monday in JAMA Pediatrics.

The researchers analyzed data from 354 U.S. hospitals participating in the American Heart Association’s Get With The Guidelines-Resuscitation registry between Jan. 1, 2000, and Dec. 12, 2012. They identified 12,404 hospitalized children with cardiac arrests who received CPR for at least two minutes. About a third — 36.2 percent — survived to hospital discharge.

The survival rates were worse for children suffering cardiac arrests overnight (33.9 percent) than during the day or evening (37.2 percent). After adjusting for variables, that represented a 12 percent drop in the chances of surviving to discharge.

Research is needed to understand and address why resuscitation practices for children at U.S. hospitals are not as successful overnight, said the study’s lead author Farhan Bhanji, M.D., an associate professor of pediatrics and pediatric critical care medicine at McGill University in Montreal, Canada.

“We don’t exactly know the reasons for the higher risk of death at nighttime, but we need to look at that further and to think how we can improve our approach so we get better outcomes at all times,” Bhanji said.

Nearly 6,000 children receive CPR at U.S. hospitals each year. The researchers said that by improving survival rates to match the highest survival reached in this study — 41.1 percent, which occurred at 1 p.m. and at 6 p.m. — would result in nearly 300 more U.S. children surviving in-hospital cardiac arrests each year.

“That’s five children a week dying from what may be a preventable cause of death, because after adjusting for many factors, it’s the fact that the event happens at night,” said Anne Marie Guerguerian, M.D., co-chair of the AHA’s Get With The Guidelines-Resuscitation Pediatric Research Task Force and a pediatric intensive care pediatrician at The Hospital for Sick Children in Toronto.

“They’re similar to the children who have cardiac arrests during the day, but it’s just that they have a deterioration that occurs at a different time,” she said.

Studies have shown a similar problem in hospitalized adults who have cardiac arrests. They, too, are less likely to survive after in-hospital resuscitation if they suffer cardiac arrests at night, versus during the day or evening. But the causes of cardiac arrest in children often are different than in adults, so this study truly needed to be done in children, Guerguerian said.

The findings, she said, suggest that the problem may be more related to organizational weaknesses at a hospital level — in other words, the system rather than related to the disease. It may be that the nighttime staffing is different than in the daytime or might point to differences in warning systems or rapid response team activation during night shifts, among other factors.

“Different models of care should be considered and potentially different approaches may need to be evaluated in future research,” Guerguerian said. “And, I think, it points to the importance of looking at this on a grand scale, across all U.S. hospitals.”