Dr. Frank McCormick of the Harvard Combined Orthopaedic Residency Program and Massachusetts General Hospital in Boston and colleagues evaluated surgical residents' sleep and awake periods.
The study participants were continuously recorded via actigraphy, a wristwatch-type instrument worn to record and store data for sleep and awake intervals that can be used to assess individual mental fatigue.
The study, published in the Archives of Surgery, found overall, residents were functioning at less than 80 percent mental effectiveness due to fatigue during a mean of 48 percent of their time awake.
In addition, the study found residents were also functioning at less than 70 percent mental effectiveness due to fatigue during a mean of 27 percent of their time awake.
Night-float residents were sleeping an average of 5.1 hours daily and day-shift residents sleeping an average of 5.7 hours daily, McCormick said.
"Resident fatigue was prevalent, pervasive and variable," the study authors said in a statement.