670 SHIFTWORK Steele et al. • RESIDENT SHIFTWORK TOLERANCE/PREFERENCE

EDUCATIONAL ADVANCES

Emergency Medicine Residents’ Shiftwork Toleranceand Preference

MARK T. STEELE, MD, O. JOHN MA, MD, WILLIAM A. WATSON, PHARMD,HAROLD A. THOMAS JR., MD

Abstract. Objectives: To determine the shiftlengths currently worked by emergency medicine(EM) residents and their shift length preferences,and to determine factors associated with EM resi-dents’ subjective tolerance of shiftwork. Methods: Asurvey was sent to EM-2 through EM-4 allopathicEM residents in May 1996. This questionnaire as-sessed the residents’ shift length worked, shift lengthpreferences, night shift schedules, and self-reportedability to overcome drowsiness, sleep flexibility, andmorningness–eveningness tendencies. When provid-ing shift length preferences, the residents were askedto assume a constant total number of hours scheduledper month. Results: Seventy-eight programs partici-pated, and 62% of 1,554 eligible residents returnedusable surveys. Current shift lengths worked were 8hours (12%), 10 hours (13%), 12 hours (37%), combi-nations of 8-hour, 10-hour, or 12-hour (34%) shifts,and other combinations (4%). Seventy-three percent

of the respondents indicated that they preferred towork 8-hour or 10-hour shifts, and only 21% pre-ferred a 12-hour shift. Shiftwork tolerance was re-corded as: not well at all (2%), not very well (14%),fairly well (70%), and very well (14%). The EM resi-dents’ eveningness preference, ability to overcomedrowsiness, sleep flexibility, younger age, and havingno children at home were all associated with greatershiftwork tolerance. Conclusions: Emergency medi-cine residents generally tolerate shiftwork well andprefer 8-hour or 10-hour shift lengths compared with12-hour shift lengths. Emergency medicine residen-cies with 12-hour shifts should consider changing res-idents’ shifts to shorter shifts. Key words: workschedule tolerance; shiftwork; morningness–evening-ness; circadian rhythms; postgraduate medical edu-cation; residents. ACADEMIC EMERGENCY MED-ICINE 2000; 7:670–673

SHIFTWORK has been identified as a majorsource of attrition in emergency medicine

(EM).1–3 Multiple factors have been identified thataffect shiftwork tolerance. These include the morn-ingness–eveningness preferences, flexibility ofsleeping patterns, and ability to overcome drowsi-ness.4,5 Age, gender, and whether children are pres-ent in the home have also been associated with tol-erance.6 To our knowledge, there are currently nodata describing EM resident tolerance of shift-work.

From the Department of Emergency Medicine, Truman Medi-cal Center, University of Missouri–Kansas City School of Med-icine, Kansas City, MO (MTS, OJM); Department of Surgery,University of Texas Health Sciences Center at San Antonio,San Antonio, TX (WAW); and Oregon Health Sciences Center,Portland, OR (HAT)Received September 9, 1999; revision received January 5,2000; accepted January 10, 2000. Presented at the SouthernMedical Association annual meeting, Charlotte, NC, November1997.Address for correspondence and reprints: Mark T. Steele, MD,Department of Emergency Medicine, Truman Medical Center,2301 Holmes Street, Kansas City, MO 64108. Fax: 816-881-6282; e-mail: steelemt@trumed1.trumanmed.org

Working different length shifts is common inEM. Two prior studies indicate that practicingemergency physicians (EPs) and EM residency fac-ulty prefer working shorter shifts.7,8 For EM resi-dents, we know of no information describing theirlengths of shifts worked or their preferences.

The objective of this study was to determine theshift lengths currently worked by EM residentsand their shift length preferences. This study alsodetermined the association of various factors withEM residents’ subjective tolerance of shiftwork.

METHODS

Study Design. The self-administered survey wasdistributed to eligible EM residents. The medicalcenter’s IRB approved the study protocol.

Study Setting and Participants. The EM-2through EM-4 EM residents at U.S. EM residencyprograms were enlisted to participate in the study.

Survey Content and Administration. The sur-

ACADEMIC EMERGENCY MEDICINE • June 2000, Volume 7, Number 6 671

TABLE 1. Night Shift Tolerance by the Residents

Not at all well 2%Not very well 14%Fairly well 70%Very well 14%

TABLE 2. Night Shifts Worked per Month by the Residents

Night Shifts/Month No. %

One to three 47 5%Four to six 369 40%Seven to ten 394 42.5%More than ten 116 12.5%

Figure 1. Shift lengths worked/preferred by the resi-dents.

vey was mailed to all U.S. EM residency programdirectors in May 1996. A follow-up mailing wasmade in June 1996. The program directors wereasked to distribute the surveys to their EM-2through EM-4 residents.

The study instrument consisted of a total of 13questions, 8 of which were the focus of this inves-tigation. This questionnaire asked the residents’shift length worked, shift length preferences, nightshift schedules, and self-reported ability to over-come drowsiness, sleep flexibility, and morning-ness–eveningness tendencies. The residents’ shiftlengths, the number of night shifts worked permonth, and the number of night shifts worked ina row were specifically determined. On a four-pointscale ranging from ‘‘not very well at all’’ to ‘‘verywell,’’ the residents were asked to rate their overalltolerance of night shifts.

Residents’ sleep flexibility and ability to over-come drowsiness were assessed with the followingquestions, respectively: ‘‘How easy is it for you totake short catnaps at odd times of the day?’’ and‘‘If you have something important to do but feelvery drowsy, how easy is it for you to overcomeyour drowsiness?’’ The residents were asked to ratetheir morningness and eveningness tendencies ona four-point scale that ranged from ‘‘definite morn-ing type’’ to ‘‘definite evening type.’’ The residentswere also requested to provide demographic infor-mation, including age, gender, year of postgradu-ate training, and the number of children living athome. In providing shift length preferences, theresidents were asked to assume a constant numberof hours scheduled per month.

Data Analysis. Medians and interquartileranges were calculated for noncontinuous varia-

bles. Univariate analysis for the various factorswas performed using chi-square analysis. Multi-variate stepwise logistic regression analysis (JMP,SAS Institute, Inc., Cary, NC) was carried out forfactors significantly correlated with shiftwork tol-erance. Ninety-five percent confidence intervals(95% CIs) were calculated using a standard for-mula; significance was set at alpha = 0.05.

RESULTS

Nearly 80% (78/99) of eligible programs partici-pated in the survey, and 62% (957/1,554) of the el-igible residents within the participating programsreturned usable surveys. The median age of therespondents was 30 years, with an interquartilerange of 30–33. Seventy-five percent of the respon-dents were male. This age and gender make it es-sentially identical to the overall demographics ofcurrent EM residents. Forty-eight percent of therespondents were EM-2s, 40% EM-3s, and 12%EM-4s. Twenty percent of the study cohort hadchildren living at home with them.

Current shift lengths worked and shift lengthpreferences are shown in Figure 1. Seventy-threepercent of the respondents indicated they prefer towork an 8-hour or 10-hour shift length, and only21% preferred 12-hour shifts. Sixty-four percent ofthe respondents working 8-hour or 10-hour shiftspreferred those lengths of shifts; 36% of the resi-dents working 12-hour shifts preferred that lengthof shift. For those residents working some combi-nation of 8-, 10-, and 12-hour shifts, 86% stated apreference for 8-hour or 10-hour shift length shifts,with 14% preferring 12-hour shifts.

Table 1 demonstrates shiftwork tolerance. Ta-ble 2 illustrates the number of night shifts workedper month by the residents, and Table 3 demon-strates the number of nights worked in a row.There was a positive correlation between shiftworktolerance and residents’ eveningness preference,ability to overcome drowsiness, sleep flexibility,

672 SHIFTWORK Steele et al. • RESIDENT SHIFTWORK TOLERANCE/PREFERENCE

TABLE 3. Nights in a Row Worked by the Residents

Nights No. %

Isolated 44 5%Two 118 13%Three 299 33%Four to ten 427 46%More than ten 27 3%

and having no children at home. Our data dem-onstrated that residents more able to overcomedrowsiness and with greater sleep flexibility weremore tolerant of shiftwork. Likewise, residentswho were more evening (as opposed to morning)oriented were more tolerant of shiftwork. Age wasinversely correlated with shiftwork tolerance. Theshift length worked (the shorter the shift, thegreater the tolerance) and the number of nightshifts worked per month consecutively (fewer nightshifts, more tolerant) were weakly correlated withshiftwork tolerance. Stepwise logistic regressionanalysis demonstrated a cumulative associationbetween these five factors, which accounted for11% of the observed variability in overall shiftworktolerance. The EM residents with eveningnesspreference, ability to overcome drowsiness, sleepflexibility, younger age, and no children at homeall had greater shiftwork tolerance.

DISCUSSION

Although three-fourths of the current EM resi-dents worked some 12-hour shifts, and more thanone-third did so exclusively, only 20% expressed apreference for 12-hour shifts. This strong prefer-ence for a shorter-length shift is similar to thatexpressed by academic faculty in a previous study7

and is similar to that expressed by a cross-sectionof practicing EPs in a study performed by Thomaset al.8 Thomas et al. surveyed 387 North CarolinaAmerican College of Emergency Physicians mem-bers and found that about one-third of the mem-bers were working 12-hour shifts and another one-third a combination of 8- and 12-hour shifts; onlyabout 10% worked 8-hour shifts exclusively. Whenasked their preferences, half stated they preferred8-hour shifts; only 12% preferred 12-hour shifts. Ina study of residency faculty the same year, a thirdworked 8-hour shifts exclusively, and another thirdworked a combination of 8- and 12-hour shifts.Overall, 75% of the faculty surveyed indicated theypreferred 8-hour shifts.

One of the reported advantages of working 12-hour shift lengths is that one has a third morecomplete days off than when working 8-hour shifts,assuming a constant number of total hours workedper month. Because of this advantage, we expectedthat EM residents would have been more likely to

prefer 12-hour shifts. This, however, was not thecase.

There is also the issue of fatigue and perfor-mance, with fatigue intuitively being greater overthe course of a 12- vs an 8-hour shift. Existinghealth care-related data are conflicting in this re-gard, but suggest that performance may suffer toa greater degree over the course of a 12-hour shiftvs an 8-hour shift.7 In an emergency departmentstudy of hazardous exposures to biological fluids,more potentially life-threatening exposures oc-curred during the last two hours of a 12-hour shift,but not during the last hours of an 8-hour shift.9

This study found that EM residents reportedtolerating night shifts well. We suspect that thismay be due in part to the fact that we were inves-tigating a group of respondents who were youngerin age and had obviously been practicing EM for amuch shorter period of time. Our results are sup-ported by data from other populations that indi-cate that younger age, no children, eveningness,sleep flexibility, and ability to overcome drowsinessare all positively correlated with the ability to tol-erate shiftwork.6

The majority of the residents reported theyworked either in the range of 4 to 6 or 7 to 10 nightshifts per month, with nearly half falling in thelatter group. This number is generally counter tothat recommended by scheduling experts, sincethis period of time is just long enough to shift cir-cadian phase to a night schedule.10 The so-called‘‘isolated night shift’’11 method lessens the circa-dian impact of night work, and working nightshifts in larger blocks has been reported to allowpeople to adjust their circadian rhythms moresmoothly; however, only about 8% of the group re-ported they used one of these formats.

LIMITATIONS AND FUTURE QUESTIONS

Limitations of this study include the possibility ofselection bias since we did not enroll about a thirdof the residents in the participating programs. Itis unlikely that this is a significant limitation sincethe age and gender of the responding residentswere essentially identical to those of the nonre-sponding residents. This study also did not deter-mine the potential specific reasons for differentshift preferences by residents. As a consequence,we do not know how or whether the advantagesand disadvantages of shorter vs longer shifts werefactored into a resident’s choosing a preferred shiftlength. Future studies should address this issue.

Another potential limitation was that we wereusing self-reported assessments of tolerance, theresidents’ morningness–eveningness preferences,sleep flexibility, and ability to overcome drowsi-

ACADEMIC EMERGENCY MEDICINE • June 2000, Volume 7, Number 6 673

ness. Self-reported morningness–eveningnesspreference has been shown to be highly correlatedto the results of the standardized morningness–eveningness questionnaire,6 which itself has beenvalidated objectively by circadian body tempera-ture studies.12 Sleep flexibility and the ability toovercome drowsiness are difficult to measure butwe did use standardized questions to assess thesevariables.

CONCLUSIONS

Emergency medicine residents prefer 8-hour or 10-hour shift lengths compared with 12-hour shiftlengths. Emergency medicine residencies with 12-hour shifts should consider changing residents’shifts to shorter shifts. Emergency medicine resi-dents with eveningness preference, ability to over-come drowsiness, sleep flexibility, younger age, andno children at home all had greater shiftwork tol-erance.

References

1. Hall KN, Wakeman MA, Levy RC, Khoury J. Factors asso-ciated with career longevity in residency-trained emergency

physicians. Ann Emerg Med. 1992; 21:291–7.2. Zun L, Kobernick M, Howes DS. Emergency physicianstress and morbidity. Am J Emerg Med. 1988; 6:370–4.3. Keller KL, Koenig WJ. Sources of stress and satisfaction inemergency medicine. J Emerg Med. 1989; 7:293–9.4. Folkard S, Monk TH. Towards a predictive test of adjust-ment to shift work. Ergonomics. 1979; 22:79–91.5. Iskra-Golec I. The relationship between circadian, person-ality, and temperature characteristics and attitudes towardsshift work. Ergonomics. 1993; 36:149–53.6. Steele MT, McNamara RM, Smith-Coggins R, Watson WA.Morningness–eveningness preferences of emergency residentsare skewed toward eveningness. Acad Emerg Med. 1997; 4:699–705.7. Steele MT, Watson WA. Emergency medicine residency fac-ulty scheduling: current practice and recent changes. AnnEmerg Med. 1995; 25:321–4.8. Thomas H, Schwartz E, Whitehead D. Eight- versus 12-hour shifts: implications for emergency physicians. Ann EmergMed. 1994; 23:1096–100.9. Macias DJ, Hafner J, Brillman JC, Tandberg D. Effect oftime of day and duration into shift on hazardous exposures tobiological fluids. Acad Emerg Med. 1996; 3:605–10.10. Whitehead DC, Thomas H, Slapper DR. A rational ap-proach to shift work in emergency medicine. Ann Emerg Med.1992; 21:1250–8.11. Michaels HE. Night shift work. Ann Emerg Med. 1984; 13:201–2.12. Horne JA, O. A self-assessment questionnaire toOstbergdetermine morningness–eveningness in human circadianrhythms. Int J Chronobiol. 1976; 4:97–110.

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TEACHING PROFESSIONALISM

Professionalism cases are available on the SAEM website, www.saem.org.These items are meant to serve as a starting point for discussion sur-rounding proper behavior and proper action. While easy answers are oftenelusive, these cases can promote provocative discussion and serve as im-portant reminders that our overriding responsibility is to serve the pa-tient’s interests.