Raleigh, N.C. — A new study in the Journal of the American Medical Association shows patients have a better chance of surviving a heart attack if it happens at a certain time of the day.

“We were able to determine that survival from cardiac arrest was significantly lower when the arrest occurred during the night or on the weekend compared to during the weekdays,” said Dr. Mary Ann Peberdy with Virginia Commonwealth University.

Researchers used data from about 86,000 cardiac arrest cases at about 500 United States hospitals and medical centers.

Patients who came in at night had only a 15 percent survival rate, compared with a 20 percent survival rate during the day. Over weekends, survival rates also decreased.

“It may be a physiological difference in patients that accounts for this study. It may be that hospital staffing patterns are different,” Peberdy said.

Lower patient survival rates were found in all areas of the hospitals, except the emergency department, which has consistent staffing 24 hours a day, 7 days a week.

Dr. Kyle Gunnerson, a critical-care specialist in Richmond, Va., said two things essential to surviving cardiac arrest depend greatly on response time: “Identifying an abnormal rhythm quickly and then delivering the appropriate therapy.”

The study recommends hospital-wide resuscitation training with an emphasis on nights and weekends.

“It's imperative that we go to the measures it will take to address this issue,” Gunnerson said.

Many hospital employees respond to only one cardiac arrest a year. Researchers said additional training could help them retain skills and improve patient safety.