Patients admitted to hospital for surgery on weekends, during the afternoon, and in the month February face a higher risk of death, new research suggests.

German researchers Dr. Felix Kork and Claudia Spies analyzed data from more than 200,000 patients who underwent surgery between 2006 and 2011 at the two University Hospital campuses of Charite Tertiary Care University Centre in Berlin.

They found that patients admitted to hospital on weekends were 22 per cent more likely to die than those who were admitted on weekdays. And they found patients admitted during the afternoon were 21 per cent more likely to die than those admitted in the morning.

The researchers also found that patients admitted to hospital in February faced a 16-per-cent increased risk of death compared with patients admitted during other months of the year.

“Several factors influence this outcome,” the researchers said in a statement released Saturday. “For example, it may be that standard of care differs throughout the day and between weekdays and weekends.”

Whilethe researchers controlled for risk factors including emergency surgery, they say the increased risk of death during certain periods“may very well be that the patients treated in the afternoon and on the weekends were more severely ill.”

A separate, larger study conducted by Dr. Hiroshi Hoshijima from Tohoku University in Japan provided further evidence that patients admitted to hospital during weekends -- who didn’t undergo surgery -- are also more likely to die than those admitted during weekdays.

Evidence proving the “weekend effect” has been piling up for approximately 20 years, with doctors acknowledging the risk of death was slightly higher for those admitted on weekends. 

Hoshijima reviewed 72 studies from around the world that included more than 55 million hospital patients. His team found that weekend admission was associated with a 15- to 17-per-cent increased risk of death compared to weekday admission.

“These differences reflect poorer quality of care in hospital during the weekends, and second, patients admitted during the weekends could be more severely ill than those admitted during a weekday,” the researchers said in a statement.

But researchers say a higher risk of death is much more likely due to poor hospital care on Saturdays and Sundays.

Both studies will be presented at the Euroanaesthesia medical congress in Stockholm.