Patient Safety Tip of the Week

November 9, 2010

12-Hour Nursing Shifts and Patient Safety



We’ve often been asked what we think about 12-hour shifts for healthcare workers from a patient safety perspective. In light of significant workforce shortages of not only nurses but also pharmacists and technologists and also economic challenges to hospitals, we are seeing the 12-hour shift implemented more and more frequently. So we’ve been searching for objective evidence of the impact of such schedules on patient safety. You’ll have no problem finding papers about the impact of 12-hour shifts on a variety of parameters. In fact, whether you are “for” or “against” such shifts you’ll have no problem finding a paper to support your position! But much of the literature is based upon anecdotal evidence (though don’t forget anecdotes and stories are often our most powerful patient safety tools!) or studies lacking valid scientific design.


The 2004 Institute of Medicine Report “Keeping Patients Safe: Transforming the Work Environment of Nurses”, recommended that policies be adopted to prevent nurses in direct patient care from working more than 12 hours in a 24-hour period and 60 hours in a 7-day week. But unlike the situation where we have put official restrictions on the hours that medical residents can work, no such limits have been formalized for nurses to date.


Much of the work on 12-hour vs. 8-hour shifts comes from industries other than healthcare. For an excellent summary of the advantages and disadvantages of 12-hour shifts in any 24/7 industry, see the white paper by Moore-Ede et al of Circadian Technologies, Inc. (Moore-Ede 2007). And, though somewhat old already, a review by Smith et al. (Smith 1998) summarizes the impact of 12-hour shifts on multiple different parameters. Advantages in many industries include increased productivity, fewer errors, fewer handoffs, increased continuity, reduced absenteeism, reduced turnover and better morale. For workers, more days off and longer breaks away from work, allowing for improved family and social life are major factors that have led many workers to like 12-hour shifts. A study done in New York City hospitals (Stone 2006) showed that nurses working 12-hour shifts were more satisfied with their jobs, had less emotional exhaustion, and less absenteeism than nurses working 8-hour shifts, all without impacting patient outcomes. One key element to worker satisfaction with 12-hour shifts seems to be how the change was developed and implemented. Where workers had a voice in developing the system, rather than having it imposed on them, satisfaction levels are much higher.


The real problem in assessing the impact of shift duration on patient safety is the same one we have in most areas of patient safety: lack of reliable, easy to collect outcome measures. It’s not like we can look at the number of defective widgets per hour and correlate that with shift duration.


Perhaps the most quoted study linking medical errors to shift duration is that by Rogers et al. (Rogers 2004). In that study nurses were randomly chosen and asked to participate in a study in which they kept log books for two 2-week periods. About 40% of those chosen responded and these were representative of the nursing population as a whole in terms of demographics and other factors. The log books contained up to 40 questions per day on days worked and 17 per day on days off. Nurses recorded not only data about hours worked, shift duration, overtime, etc. but also included self-reported errors and near errors. The study clearly showed increasing error rates with increasing duration of shifts. The odds ratio for making an error was 3.29 for nurses working more than 12.5 consecutive hours and the odds ratio was 2.06 for nurses working any time longer than their scheduled shift. Of the errors reported, 58% involved medication administration, 18% procedural errors, 12% charting errors, and 7% transcription errors.


The same group later demonstrated similar findings in a randomly selected sample of critical care nurses (Scott 2006). That study also found a correlation between shift duration and nurses’ difficulty staying awake, though they were not able to demonstrate an association between that and the increased risk of errors.


In both those studies, the other striking (but no surprise to us) finding was that nurses almost never go home at the end of a scheduled shift. In fact, in the second study only 1 out of 502 respondents reported leaving on time at the end of a shift. Nurses worked on average 55 minutes longer per shift and two-thirds of the nurses worked overtime 10 or more times during the 4-week study periods.


So what, if anything, is wrong with these studies and why aren’t we restricting duration of nursing shifts? The study used self-reported errors and near errors as outcome measures. We don’t have a problem with that. We know that incident reporting systems and even medication error reporting systems significantly underreport errors and that anonymous reporting systems do a much better job of capturing errors and events. The biggest concern is that there are multiple confounding variables that may have had an impact on the results of these studies.


First, and formost, is that the studies did not include strict 12-hour shifts (though as the studies pointed out, there may be no such practical entity as a strict 12-hour shift). Obviously the amount of overtime worked by the nurses likely had a big impact. We also are not told about 2 very important factors that may have played a role: (1) handoffs and (2) effect of consecutive days worked.


One of the potential beneficial aspects of 12-hour shifts is the reduction in handoffs. In fact, in most industries that reduction in handoffs is touted as the most important benefit of 12-hour shift. Instead of the three handoffs seen with 8-hour shifts, you only have two handoffs with 12-hour shifts. And, just as importantly, you are typically handing off to the same individuals that your received a handoff from at the start of your shift (adding an element of “I want my handoff to be as good as the one I expect to get”). We’ve talked about the problems that arise as the result of “fumbled” handoffs in numerous columns (see our April 2010 Patient Safety Tip of the Week “Update on Handoffs”, which has links to all the other handoff columns).


The second is a very interesting phenomenon seen when one looks at error rates by day of the week. It turns out that in a typical 5-day work week you make more errors toward the end of the week. We’ll call this the “consecutive day phenomenon”. A study on shift workers in fields other than healthcare (Folkard 2003) showed that the risk of incidents increased each consecutive day worked . For example, on average for night shifts risk was 6% higher on the second night, 17% higher on the third night, and 36% higher on the fourth night (for morning/day shifts the corresponding risks were 2%, 7% and 17%). That same study demonstrated that risks are not uniform throughout the day but are greater at certain times, especially at night, and even vary based upon temporal relationship to breaks. Those authors stress that all these factors (number of successive night shifts, length of night shifts, and provision of breaks) must all be considered in combination. They note it is conceivable that a 12-hour night shift with frequent rest breaks might well prove safer than an 8-hour shift with only one mid-shift break.


In an excellent 3-part series this year “Is It Time to Pull the Plug on 12-Hour Shifts?” by Geiger-Brown and colleagues, Part 1 describes the negative aspects of 12-hour shifts on multiple different parameters. These include not only potential patient outcomes, but also needlestick injuries, musculoskeletal and other work-related injuries, and increased rates of motor vehicle collisions or near-misses while driving home from extended shifts. They also discuss potential health consequences of long-term sleep deprivation. Part 2 describes the barriers to reverting to shorter shifts, not the least of which is that nurses often like the 12-hour shifts for a variety of reasons. And Part 3 is an excellent set of recommendations for organizations to take to mitigate the potentially negative effects of 12-hour shifts if you have to live with them. Key amongst those recommendations is limiting the shift (i.e. no overtime and avoiding things like meetings at the end of shifts) and respecting days off (not calling nurses in to work on their scheduled days off). They also recommend use of scheduling software that takes into account health conditions and other factors that may overtax nurses working long shifts. Improvements in physical layouts and the environment can also remove some of the stressors that contribute to fatigue. They also have some great suggestions for protecting nurses working the night shifts (use of “buddy” systems, planned “power naps”, avoiding certain types of tasks during the body’s circadian nadir around 2-4 AM, and encouraging nurses to speak up when they are tired). Very important are some other suggestions relating to health of the nurses, such as having food sources other than vending machines, and having caffeinated beverages available up to (but not beyond) 11 PM. They even have recommendations about appropriate use of sunglasses on leaving the hospital in the morning.


Communication when working in a 12-hour shift environment may also be challenging. As above, you need to make sure you do not schedule meetings or training sessions at either end of the 12-hour shift so you have to make other accommodations for those. Many have suggested that other means of communication (written, email, web-based, etc.) may need to be implemented when 12-hour shifts become the norm. Also, when nurses are away for longer periods of time (one of the “advantages” of 12-hour shifts that many nurses like) there may be a need for reorienting when the nurse returns.


One observation noted in multiple studies is that though fatigue and slowed cognitive processes were documented with various tools, nurses (or residents or other healthcare workers) were often able to rise to the occasion when faced with serious medical problems. It seems that errors tend to be more problematic with more mundane, repetitive sorts of tasks. The paradox between fatigue and slowed cognitive function vs. productivity has also been seen for medical residents. Whereas Dula et al (Dula 2001) had demonstrated that residents’ cognitive ability declines over the course of consecutive overnight shifts, another study (Jeanmonod 2009) demonstrated that for ER residents productivity (defined as number of patients seen per hour) actually went up on consecutive days through at least 5 days.


Multiple studies have also demonstrated that people (in any industry, not just healthcare) tend to underestimate their levels of fatigue and impairment compared to their performance on formal testing. Some day we will have the equivalent of the brief “sobriety” test that can rapidly identify healthcare workers who are impaired by fatigue.


There obviously are very many unanswered questions regarding 12-hour shifts for nurses or other healthcare professionals. A lot has changed since some of the field studies on impact of these shifts was first done. Undoubtedly, our high tech tools (bedside medication verification by barcoding, CPOE, etc.) have changed the environment but we don’t know whether that mitigates or exacerbates the problems associated with 12-hour shifts. We’re only likely to solve this with a well-designed study with hard outcome parameters done in a setting where a legitimate control group can be used (for example, implementing 12-hour shifts on one or several med/surg floors where the other comparable floors maintain their current 8-hour shifts). Even then, a way to account for all the potentially confounding factors noted above must be found.


Our best advice for the present is to be wary of potential patient safety issues if you are using 12-hour nursing shifts and implement the recommendations in the Geiger-Brown articles.



Updates: See our February 2011 What’s New in the Patient Safety World column “Update on 12-hour Nursing Shifts” and our November 13, 3012 Patient Safety Tip of the Week “The 12-Hour Nursing Shift: More Downsides” and our July 29, 2014 Patient Safety Tip of the Week “The 12-Hour Nursing Shift: Debate Continues” and our October 2014 What’s New in the Patient Safety World column “Another Rap on the 12-Hour Nursing Shift”.








IOM (Institute of Medicine). Page A (ed). Keeping Patients Safe: Transforming the Work Environment of Nurses.Washington: National Academies Press, 2004



Moore-Ede M, Davis W, Sirois W. Advantages and Disadvantages of Twelve-Hour Shifts: A Balanced Perspective (white paper). CIRCADIAN® 2007.



Smith L, Folkard S, Tucker P, Macdonald I. Work shift duration: a review comparing eight and 12 hour shift systems. Occup Environ Med 1998; 55: 217-229



Stone PW. Du Y. Cowell R. Amsterdam N. Helfrich TA. Linn RW. Gladstein A. Walsh M. Mojica LA. Comparison of Nurse, System and Quality Patient Care Outcomes in 8-Hour and 12-Hour Shifts. Medical Care 2006; 44(12): 1099-106, 2006 Dec,_System_and_Quality_Patient.7.aspx



Rogers AE, Hwang WT, Scott LD, Aiken LH, Dinges DF. The Working Hours Of Hospital Staff Nurses And Patient Safety. Both errors and near errors are more likely to occur when hospital staff nurses work twelve or more hours at a stretch.
Health Affairs 2004; 23(4): 202-212  July/August 2004;



Scott LD, Rogers AE, Hwang WT, Zhang Y. Effects of Critical Care Nurses’ Work Hours on Vigilance and Patients’ Safety. Am J Crit Care 2006 15(1): 30-37



Folkard S, Tucker P. Shift work, safety and productivity. Occupational Medicine 2003; 53: 95-101



Geiger-Brown J, Trinkoff AM. Is It Time to Pull the Plug on 12-Hour Shifts? Part 1. The Evidence. Journal of Nursing Administration 2010; 40(3): 100-2, 2010 Mar



Lothschuetz Montgomery K. Geiger-Brown J.  Is It Time to Pull the Plug on 12-Hour Shifts? Part 2. Barriers to change and executive leadership strategies.

Journal of Nursing Administration. 40(4):147-9, 2010 Apr.



Geiger-Brown J. Trinkoff AM. Is It Time to Pull the Plug on 12-Hour Shifts? Part 3. harm reduction strategies if keeping 12-Hour Shifts. Journal of Nursing Administration 2010;  40(9): 357-9, 2010 Sep



Dula DJ, Dula NL, Hamrick C, Wood GC. The effect of working serial night shifts on the cognitive functioning of emergency physicians. Ann Emerg Med 2001; 38(2): 152-155



Jeanmonod R, Damewood S, Brook C. Resident Productivity: trends over consecutive shifts. Int J Emerg Med 2009; 2: 107-110













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