MONDAY, June 2, 2014 (HealthDay News) — The timing of your surgery or hospital admission could affect your risk of death, according to new research.

One study found that a patient’s risk of death after surgery is highest on weekends, afternoons and in February. Another study concluded that patients admitted to hospitals on weekends have a higher risk of death than those admitted on weekdays.

The studies were scheduled for presentation this weekend at the European Society of Anaesthesiology meeting in Stockholm, Sweden.

In the first study, researchers analyzed data from nearly 219,000 patients who had surgery in Berlin, Germany, between 2006 and 2011. Patients operated on in the afternoon were 21 percent more likely to die compared with those who had surgery at other times of the day.

Surgery on the weekend carried a 22 percent higher risk of death than surgery on weekdays, the study found. And patients operated on in February were 16 percent more likely to die than those who had surgery in all other months.

“Several factors may have influenced this outcome. For example, it may be that standard of care differs throughout the day and between weekdays and weekends,” wrote Dr. Felix Kork and Claudia Spies, of Charite-University Medicine Berlin, and colleagues.

“Although we controlled for risk factors including emergency surgery in our study, it may very well be that the patients treated in the afternoon and on the weekends were more severely ill. We need more data to draw conclusions regarding seasonal variation in postoperative outcome,” they said in a society news release.

The authors added that the findings show the need to further improve patient safety. However, research presented at meetings is considered preliminary until published in a peer-reviewed medical journal.

In the second study, researchers analyzed data from 55 million hospital patients worldwide. They found those admitted on weekends were 15 percent to 17 percent more likely to die than those admitted on weekdays.

“There are at least two potential explanations for our results,” said Dr. Hiroshi Hoshijima of Tohoku University in Sendai, Japan, and colleagues. “First, these differences reflect poorer quality of care in hospitals on the weekend, and second, patients admitted on the weekend could be more severely ill than those admitted on a weekday,” Hoshijima’s team suggested.

“We believe that poorer care at the weekends is the much more likely explanation,” the study authors said in the news release.

More information

The U.S. National Institutes of Health has more about surgery.