Study shows 12-hour shifts increase errors

Research on impact of long hours on nurses

A study published on-line by the journal Health Affairs1 indicates that hospital nurses working shifts of 12.5 hours or more are three times more likely to make an error than nurses working shorter shifts.

The study is based on data from 393 members of the American Nurses Association who kept a log of their hours worked, overtime, days off, and sleeping patterns for 28 days.

The researchers found that in 39% of the 5,317 total shifts worked, the nurses worked at least 12.5 consecutive hours, but only 7% involved mandatory overtime. And 14% of the respondents reported working 16 or more consecutive hours at least once during the four-week period.

On average, participants worked 55 minutes longer per day than scheduled and 40.2 hours per week.

They reported making a total of 199 errors and 213 near errors during the period. About half the errors involved medication administration, while others involved procedural, charting, and transcription errors.

"Our analysis showed that work duration, overtime, and number of hours worked per week had significant effects on errors,"1 the authors wrote. In fact, they noted, the likelihood of making an error increased with longer work hours and was three times higher when nurses worked shifts lasting 12.5 hours or more.

One of the reasons for the study, the lead authors noted, is that there was not a great deal in the literature about the prevalence of extended work hours for nurses or the effects on patient safety.

"There really is nothing, though there are lots of studies on physicians — even though nurses are the largest group of health care providers," observes Ann E. Rogers, PhD, RN, FAAN, an associate professor at the University of Pennsylvania School of Nursing in Philadelphia, and the study’s lead author.

Combating fatigue

The original impetus for the study, Rogers notes, was her desire to do a pilot study to test a fatigue countermeasures program for nurses.

"It has been used in transportation, in the nuclear power industry, and should be applicable for any group doing 24-hour-a-day type work," she asserts. "I found out that we didn’t know enough [about nurses’ working conditions], so we had to go out and get the data."

Now that Rogers has scientific data that demonstrate the long hours nurses work, they will inform different recommended interventions.

"For example, one of the things to look at is the timing of ingestion of caffeine; I would suggest it at different times during 12- and eight-hour shifts. This turned out to be very important information," she explains.

It didn’t surprise Rogers that there was a greater risk of making an error after 12 hours.

"In studies of truck drivers or factory workers, we start to see accidents become more prevalent after nine hours or so," Rogers points out. "When people who work in nuclear plants, for example, work extensive overtime, they misread dials and things like that, so it would seem that nurses really aren’t different than other human beings."

It was critical, she adds, that the diaries the participants kept were totally anonymous.

"I absolutely did not know anybody’s name or address," Rogers asserts. "If these were not anonymous, it would have affected the sharing of errors and near errors."

The questions were modeled based on the researchers’ experience with sleep research, as well as with adult patients and nurses.

"For example, my background in sleep research tells me that everyone has trouble staying alert between 4 a.m. and 6 a.m.," she adds.

"Even if they are motivated and rested, they still have trouble. So we wanted to know, for instance, if the nurses were having trouble being alert."

As for the most significant finding of the study, Roger says, "Basically, it is hazardous for patients when nurses work 12 or more consecutive hours. It is hazardous for patients when nurses work overtime — and they do that almost every day they work. So we need to pay closer attention to the hours they work and try to reduce overtime and long shifts."

As for her pilot study to test the fatigue countermeasures program for nurses, Rogers says, "It will take a good year or so" before she will be able to begin the program.


1. Rogers AE, Hwang W-T, Scott LD, et al. The working hours of hospital staff nurses and patient safety. Health Affairs July/August 2004. DOI: 10.1377/ hlthaff.23.4.202.

Need More Information?

For more information, contact:

• Ann E. Rogers, PhD, RN, FAAN, Associate Professor, University of Pennsylvania School of Nursing, 420 Guardian Drive, Philadelphia, PA 19106-6096. Phone: (215) 573-7512. Fax: (215) 573-8794.