A new study reveals that hospital patients who suffer cardiac arrest at night or on the weekend are less likely to survive than those who have a heart attack during weekdays or weekday evenings.

“Hospital simply don’t work the same at night as they do during the day. There is enough data out there to suggest that this may be a process issue that is at least contributing, and probably contributing substantially,” study author Dr. Mary Ann Peberdy, an associate professor of internal medicine and emergency medicine at Virginia Commonwealth University in Richmond.

Dr. Peberdy and colleagues analyzed data covering period from January 1, 2000 through February 1, 2007, provided by 507 hospitals in the National Registry of Cardiopulmonary Resuscitation, sponsored by the American Heart Association.

The data involved 86,748 adults who suffered heat attacks while in the hospital. Of these cardiac events, 58,593 happened during day or evening hours, including weekends. The remaining 28,155 events happened during the night, also including weekend nights.

The researchers defined day/evening as 7 a.m. to 10:59 p.m., night as 11 p.m. to 6:59 a.m., and weekend as 11 p.m. Friday to 6:59 a.m. Monday.

The study revealed that those who suffered cardiac arrests during a weekday had a 24-hour recovery rate of 35.4 percent, and a 19.8 percent chance of surviving until they were discharged from the hospital. On the other hand, for those who suffered cardiac arrest at night, those rates fell to 28.9 percent and 14.7 percent. In addition, those who suffered from cardiac arrests during the weekend had only a 14.6 chance of surviving.

Overall survival was 14.7 percent for nights-weekends, and 19.8 percent for weekdays.

Dr Peberdy offered several potential explanations for the time-related differences in outcome: fewer supervisory personnel at night and on weekends, decreased hospital staffing at night and on weekends, use of less experienced healthcare personnel at night and on weekends and fewer hospital visitors to alert hospital staff when patients have cardiac arrests.

She also said the findings “should be a pretty big wake-up call to urge hospitals to critically evaluate how they are performing resuscitation. It may well be possible that there is a less effective and less efficient response at night. This paper really needs to go to hospital, and the people who run them.”

This study follows a research conducted by Dr. Paul Chan of University of Michigan on January, which suggested that almost a third of patients who suffer cardiac arrest in hospital do not get a defibrillator-delivered shock to make the heart beating again within two minutes how the American Heart Association recommends.

Dr. Peberdy’s findings were published in today’s issue of the Journal of the American Medical Association.