Doctors call it the “weekend effect.” Patients in the hospital are more likely to die off-hours — whether it’s due to a brain bleed, a heart attack or a clot in the lungs.

New research on cardiac arrest in the hospital now asks: Has the “weekend effect” changed in recent years, as treatment has gotten better?

“We know that survival trends have improved in past decade or so,” said Dr. Uchenna Ofoma, assistant professor of medicine at Temple University and a critical care physician at Geisinger Health System in Danville, Pennsylvania. “The question now becomes … what happens to the disparities? Has it remained the same? Is it narrowing?”

Ten years after a 2008 study showed lower survival rates during nights and weekends for in-hospital cardiac arrest, Ofoma published a new study Monday in the Journal of the American College of Cardiology. The new study builds on that previous research, finding that treatment has indeed gotten better, but we haven’t closed the nights-and-weekends gap.

Between 2000 and 2014, weekday survival jumped from 16% to 25.2%, while weekend and weeknight survival rose from 11.9% to 21.9%, according to the new study’s risk-adjusted numbers.

There was no significant change in the gap between weekday and off-hours survival, the study said. About half of patients in the study — more than 150,000 patients from 470 US hospitals — experienced cardiac arrest off-hours.

Weekend worrier

“We’re able to point out that the problem exists without really having great insight as to why,” said Dr. Seth Goldstein, a pediatric surgical fellow at Johns Hopkins Hospital.

Though not involved in the new study, Goldstein’s own research found that children admitted to the hospital for common, urgent surgeries on weekends had a higher adjusted risk of death, blood transfusion and other complications.

Perhaps hospitals are understaffed and doctors are fatigued during off-hours, Goldstein said. It could also be that patients who come to the hospital on nights and weekends are worse off to begin with, he added. For example, those might be times when people are more likely to drink and injure themselves, resulting in severe surgeries.

Similarly, in the new study, the patients whose hearts stopped off-hours could have been sicker in ways that weren’t measured by the study, Ofoma and his colleagues wrote. Their cardiac arrests were also less likely to be witnessed by someone else in the hospital.

These patients were also more likely to flatline — which can’t be treated with a shock to the heart. However, this still wouldn’t completely explain the difference between the two survival rates, according to the 2008 study on cardiac arrest.

These patients are different from people who experience cardiac arrest or heart attacks outside of the hospital. For them, having someone witness the event — and better yet, having someone perform CPR or defibrillation — was a key predictor of survival, research shows. And time is of the essence: The longer it takes for an ambulance to get there, the worse the outcome.

Still, these patients are more likely to die and less likely to get invasive cardiac procedures on weekends, according to one study.

Ofoma believes that there’s a way to tackle the survival gap on nights and weekends: look at which hospitals have the smallest difference, and figure out what they’re doing right.

Ready to go

Goldstein believes that hospitals can close the gap by changing how they run — including more staffing and better ways of alerting doctors and nurses if their patients take a turn for the worst.

“The number of patients that we’re responsible for at any one time is higher during the less desirable shifts,” Goldstein said.

And it’s not just doctors and nurses, he added. “It is more difficult in a hospital to get laboratory values, x-rays done, EKGs performed (at night) than it is during the day.”

The proof of principle, he said, are in fields like trauma and transplant surgery, which don’t have the same “day-night cycle” as other fields.

One study of Pennsylvania’s trauma system, for example, showed no weeknight or weekend effect.

“They need to be ready to go,” he said.