MJA • Volume 185 Number 7 • 2 October 2006
Medical staff working the night shift: can naps help?
R Doug McEvoy and Leon L Lack
Napping at night may benefit both health professionals and their patients
elivering medical care is a 24-hour business that inevita-
bly involves working the night shift. However, night shift
requires the health professional to work when the body’s
clock (circadian system) demands sleep. Added to this is the
problem of “sleep debt”, arising from both prolonged prior
wakefulness on the first night shift and cumulative sleep debt
after several nights’ work and repeated unsatisfactory daytime
sleeps. A further aggravation, particularly for trainee medical staff
in teaching hospitals, has been the demand for excessive work
hours across the working week. As has been dramatically shown
in recent well controlled studies, the net result of this assault on
the sleep of health professionals can be impaired patient safety,1
and the health and safety of health professionals themselves.2
The good news is that health organisations and regulators are
beginning to treat the matter seriously. In Australia, the United
States and Europe, work hours of medical staff have recently
been shortened by government regulation, and bodies such as
the Australian Medical Association and professional colleges are
advising their members on strategies to improve their sleep
health and thus work safety. A recent publication prepared by the
Royal College of Physicians (London) (RCP), Working the night
shift: preparation, survival and recovery. A guide for junior doctors, is
an excellent example.3 One proposed countermeasure for exces-
sive sleepiness is the use of strategically placed naps both before
and during the night shift. But does napping either before or
during the night shift reduce sleepiness and improve perform-
ance, and, if so, how practical is it?
There are two important, independent mechanisms of sleep
and sleepiness that hold the key to these questions.4 Probably the
more potent mechanism impairing night-shift alertness is the
circadian system. For most individuals, even those working
permanent night shift, the circadian system is in sleep mode
during the night. This causes slowed reactions, increased feelings
of fatigue, impaired concentration, and increased sleep propen-
sity. The second important mechanism affecting night-time alert-
ness is homeostatic sleep drive. This increases in intensity the
longer we are awake and, like appetite which is sated by eating,
homeostatic sleep drive is reduced by sleeping. If the first night
shift starts at midnight following a normal wake time at about
8 am, about 16 hours of wake sleep debt has already been
accrued and the rest of the night shift will be performed under
intense homeostatic, in addition to circadian, sleep drive. Per-
formance decrements during this night period can be similar to
those measured in the daytime with a blood alcohol concentra-
tion of 0.05%–0.10%.5 Day sleep in the home environment is
likely to be shorter and less effective than night sleep so, even
though second and subsequent night shifts may follow fewer
wakeful hours (8–10 hours), homeostatic sleep drive is likely to
remain elevated during night shifts because of incomplete repay-
ment of the previous sleep debt.
To a limited extent, it is possible to “bank” sleep (or pay off
residual sleep debt) before the first night shift, potentially reducing
subsequent night-time homeostatic sleep drive and improving
alertness and work safety. A long (1–2 hours) nap in the afternoon,
350MJA • Volume 185 Number 7 • 2 October 2006
as recommended in the RCP report, is best. Afternoon sleep is
more efficient than early evening sleep as it uses the natural
afternoon “dip” in circadian physiology6 and avoids the risk of
post-sleep grogginess or sleep inertia impinging on the start of
night duty. Between subsequent night shifts, the aim should be to
maximise daytime sleep length (at least 7 hours) and efficiency by
including the afternoon sleepy period (1–4pm).
What about napping during a night shift to improve alertness
and reduce errors and accidents? Brief afternoon naps of 10–30
minutes (so-called power naps) improve alertness and perform-
ance. We compared afternoon naps of 5, 10, 20, and 30 minutes
of total sleep.7 The 10 minute sleep (about a 15 minute nap
opportunity) produced improvements over the 3 hour post-nap
period in all eight alertness and performance measures, without
any of the post-nap impairment of sleep inertia that followed the
20 and 30 minute naps. Whether these results would be
replicated at, say, 3am in a night-shift environment, with
considerably greater homeostatic and circadian sleep drive, is
now being tested.
Only a few studies have measured the effects of night-shift
napping. Long naps of about 2 hours appear as effective at about
3 am as at 3pm.8 However, 1–2 hour naps were followed by
sleep inertia, during which alertness was impaired for up to an
hour.9 Longer naps, although beneficial once sleep inertia has
been dissipated, may be used reluctantly by medical staff wishing
to maintain continuity of patient care.10 Briefer naps (18–26
minutes) have also improved performance in night-shift environ-
ments.11 Therefore, the picture emerging from night-shift nap-
ping studies is similar to that from the afternoon studies. Very
brief naps (10–15 minutes of sleep) may improve alertness
immediately without the negative effects of sleep inertia. How
long this improvement lasts and what is the optimal nap length
on the night shift remains to be determined.
In the meantime, as recommended in the recent RCP guide,
health professionals who work night shift should, for the sake of
their own health and safety and that of their patients, consider
the benefits of night-shift napping. Optimal benefit and a higher
take-up rate are likely for sleep lengths of 10–15 minutes.
R Doug McEvoy, MD, FRACP, BMedSc, Professor,1 Director2
Leon L Lack, BA, PhD, Consultant Psychologist,2 Professor3
1 School of Medicine, Flinders University, Adelaide, SA.
2 Adelaide Institute for Sleep Health, Repatriation General Hospital,
3 School of Psychology, Flinders University, Adelaide, SA.
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motor vehicle crashes among interns. N Engl J Med 2005; 352: 125-134.
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recovery. A guide for junior doctors. London: Royal College of Physicians
of London, 2006. http://www.rcplondon.ac.uk/pubs/books/nightshift/
index.asp (accessed Aug 2006).
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11 Purnell MT, Feyer AM, Herbison GP. The impact of a nap opportunity
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