Your chances of surviving a cardiac arrest while in a hospital are worse at night and on weekends, and experts are baffled as to why. While some progress has been seen in recent years, there still is a significant gap between the off-hours to on-hours rate of survival to discharge.

Investigators with the American Heart Association’s Get With the Guidelines-Resuscitation program looked at more than 157,000 adults on the program’s registry. Just over 52 percent of them had a cardiac arrest during off-hours, defined as any time outside Monday to Friday, 7 a.m. to 11 p.m.

Between 2000-2014, the survival to discharge rate was about 17 percent for those in the off-hours versus more than 20 percent during on-hours. That rate has improved slightly, but the gap persists, the team reported in the Journal of the American College of Cardiology.

A closer look showed the biggest area of concern was during the post-resuscitation period on nights and weekends, and they identified several factors that may be the cause. They suggested there may be fewer and less experienced physicians on duty. Also, nurse-to-patient ratios typically are low during these times.

The researchers said the problem could be shift work, noting that working at night has been shown to impact psychomotor skills and performance, which are essential in cardiopulmonary resuscitation.

The team said a more careful allocation of resources would help and they suggested the hospitals must first identify the barriers to prompt care so in-house protocols can be adjusted. And don’t dawdle. When it comes to these remedies, just as with patients having cardiac arrests, time is of the essence.