Working memory capacity is decreased in sleep-deprived internal medicine residents.
BACKGROUND
Concerns about medical errors due to sleep deprivation during residency training led the Accreditation Council for Graduate Medical Education to mandate reductions in work schedules. Although call rotations with extended shifts continue, effects on resident sleep-wake times and working memory capacity (WMC) have not been investigated.


OBJECTIVE
The objective of this study was to measure effects of call rotations on sleep-wake times and WMC in internal medicine residents.


METHODS
During 2 months of an internal medicine training program adhering to ACGME work-hour restrictions (between April 2006 and June 2007), residents completed daily WMC tests, wore actigraphy watches, and logged their sleep hours. This observational study was conducted during a call month requiring 30-hour call rotations every fourth night, whereas the noncall month, which allowed sleep/wake cycle freedom, was used as the control.


METHODS
Sleep hours per night and WMC testing.


RESULTS
Thirty-nine residents completing the study had less sleep per night during their call month (6.4 vs 7.3 h per night noncall, p < 0.001) and sleep per night varied from 3.7 to 10.1 hours. Call rotation caused greater self-assessed sleepiness and reduced WMC recall scores (-2.6/test, p < 0.05), and more math errors occurred when on call (+1.07/test, p < 0.04). Full recovery of WMC did not occur until the fourth day after call. On-call rotation on the first month had a confounding detrimental effect on WMC.


CONCLUSIONS
A month of call rotations reduced overall sleep per night; sleep hours per night were variable, and WMC was adversely affected. Decreased WMC could explain impaired judgment during sleep deprivation, although clinical error rates were not evaluated.
Gohar
Ashraf
A
Division of Pulmonary, Allergy, and Critical Care, University of Minnesota and Regions Hospital, St. Paul, MN, USA.
Adams
Alexander
A
Gertner
Elie
E
Sackett-Lundeen
Linda
L
Heitz
Richard
R
Engle
Randall
R
Haus
Erhard
E
Bijwadia
Jagdeep
J
D056044:Actigraphy / Q000379:methods / Q000706:statistics & numerical data; D000328:Adult; D002983:Clinical Competence / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007388:Internal Medicine; D007396:Internship and Residency / Q000706:statistics & numerical data*; D008297:Male; D019300:Medical Errors / Q000517:prevention & control; D008569:Memory Disorders / Q000209:etiology; D008570:Memory, Short-Term; D008910:Minnesota; D012650:Self Disclosure; D012892:Sleep Deprivation / Q000150:complications*; D011795:Surveys and Questionnaires; D013647:Task Performance and Analysis; D014940:Work Schedule Tolerance; D055815:Young Adult