CHRISTMAS 2010: RESEARCH
Beauty sleep: experimental study on the perceived health
and attractiveness of sleep deprived people
John Axelsson, researcher,1,2 Tina Sundelin, research assistant and MSc student,2 Michael Ingre, statistician
and PhD student,3 Eus J W Van Someren, researcher,4 Andreas Olsson, researcher,2 Mats Lekander,
researcher1,3
ABSTRACT
Objective To investigate whether sleep deprived people
are perceived as less healthy, less attractive, and more
tired than after a normal night’s sleep.
Design Experimental study.
Setting Sleep laboratory in Stockholm, Sweden.
Participants 23 healthy, sleep deprived adults (age 18-
31) who were photographed and 65 untrained observers
(age 18-61) who rated the photographs.
Intervention Participants were photographed after a
normal night’s sleep (eight hours) and after sleep
deprivation (31 hours of wakefulness after a night of
reduced sleep). The photographs were presented in a
randomised order and rated by untrained observers.
Main outcome measure Difference in observer ratings of
perceived health, attractiveness, and tiredness between
sleep deprived and well rested participants using a visual
analogue scale (100 mm).
Results Sleep deprived people were rated as less healthy
(visual analogue scale scores, mean 63 (SE 2) v 68 (SE 2),
P<0.001), more tired (53 (SE 3) v 44 (SE 3), P<0.001), and
less attractive (38 (SE 2) v 40 (SE 2), P<0.001) than after a
normal night’s sleep. The decrease in rated health was
associated with ratings of increased tiredness and
decreased attractiveness.
Conclusion Our findings show that sleep deprived people
appear less healthy, less attractive, and more tired
compared with when they are well rested. This suggests
that humans are sensitive to sleep related facial cues,
with potential implications for social and clinical
judgments and behaviour. Studies are warranted for
understanding how these effects may affect clinical
decision making and can add knowledge with direct
implications in a medical context.
INTRODUCTION
The recognition [of the case] depends in great measure
on the accurate and rapid appreciation of small points
in which the diseased differs from the healthy state
Joseph Bell (1837-1911)
Good clinical judgment is an important skill in medical
practice. This is well illustrated in the quote by Joseph
Bell,1 who demonstrated impressive observational and
deductive skills. Bell was one of Sir Arthur Conan
Doyle’s teachers and served as a model for the fictitious
detective Sherlock Holmes.2 Generally, human
judgment involves complex processes, whereby
ingrained, often less consciously deliberated responses
from perceptual cues are mixed with semantic calculations
to affect decision making.3 Thus all social interactions,
including diagnosis in clinical practice, are
influenced by reflexive as well as reflective processes
in human cognition and communication.
Sleep is an essential homeostatic process with well
established effects on an individual’s physiological,
cognitive, and behavioural functionality4-7 and long
term health,8 but with only anecdotal support of a
role in social perception, such as that underlying judgments
of attractiveness and health. As illustrated by the
common expression “beauty sleep,” an individual’s
sleep history may play an integral part in the perception
and judgments of his or her attractiveness and
health. To date, the concept of beauty sleep has lacked
scientific support, but the biological importance of
sleep may have favoured a sensitivity to perceive
sleep related cues in others. It seems warranted to
explore such sensitivity, as sleep disorders and disturbed
sleep are increasingly common in today’s 24
hour society and often coexist with some of the most
common health problems, such as hypertension910 and
inflammatory conditions.11
To describe the relation between sleep deprivation
and perceived health and attractiveness we asked
untrained observers to rate the faces of people who
had been photographed after a normal night’s sleep
and after a night of sleep deprivation.We chose facial
photographs as the human face is the primary source of
information in social communication.12 A perceiver’s
response to facial cues, signalling the bearer’s emotional
state, intentions, and potential mate value, serves
to guide actions in social contexts and may ultimately
promote survival.13-15 We hypothesised that untrained
1Osher Center for Integrative
Medicine, Department of Clinical
Neuroscience, Karolinska Institutet,
17177 Stockholm, Sweden
2Division for Psychology,
Department of Clinical
Neuroscience, Karolinska Institutet
3Stress Research Institute,
Stockholm University, Stockholm
4Netherlands Institute for
Neuroscience, an Institute of the
Royal Netherlands Academy of
Arts and Sciences, and VU
Medical Center, Amsterdam,
Netherlands
Correspondence to: J Axelsson
john.axelsson@ki.se
Cite this as: BMJ 2010;341:c6614
doi:10.1136/bmj.c6614
BMJ | ONLINE FIRST | bmj.com page 1 of 5
observers would perceive sleep deprived people as
more tired, less healthy, and less attractive compared
with after a normal night’s sleep.
METHODS
Using an experimental design we photographed the
faces of 23 adults (mean age 23, range 18-31 years, 11
women) between 14.00 and 15.00 under two conditions
in a balanced design: after a normal night’s sleep (at
least eight hours of sleep between 23.00-07.00 and
seven hours of wakefulness) and after sleep deprivation
(sleep 02.00-07.00 and 31 hours of wakefulness). We
advertised for participants at four universities in the
Stockholm area. Twenty of 44 potentially eligible people
were excluded. Reasons for exclusion were
reported sleep disturbances, abnormal sleep requirements
(for example, sleep need out of the 7-9 hour
range), health problems, or availability on study days
(themain reason).Wealso excluded smokers and those
who had consumed alcohol within two days of the protocol.
One woman failed to participate in both conditions.
Overall, we enrolled 12 women and 12 men.
The participants slept in their own homes. Sleep
times were confirmed with sleep diaries and text messages.
The sleep diaries (Karolinska sleep diary)
included information on sleep latency, quality, duration,
and sleepiness. Participants sent a text message
to the research assistant by mobile phone (SMS) at bedtime
and when they got up on the night before sleep
deprivation. They had been instructed not to nap. During
the normal sleep condition the participants’ mean
duration of sleep, estimated from sleep diaries, was
8.45 (SE 0.20) hours. The sleep deprivation condition
started with a restriction of sleep to five hours in bed;
the participants sent text messages (SMS) when they
went to sleep and when they woke up. The mean duration
of sleep during this night, estimated from sleep
diaries and text messages, was 5.06 (SE 0.04) hours.
For the following night of total sleep deprivation, the
participants were monitored in the sleep laboratory at
all times. Thus, for the sleep deprivation condition,
participants came to the laboratory at 22.00 (after 15
hours of wakefulness) to be monitored, and stayed
awake for a further 16 hours. We therefore did not
observe the participants during the first 15 hours of
wakefulness, when they had had a slightly restricted
sleep, but had good control over the last 16 hours of
wakefulness when sleepiness increased in magnitude.
For the sleep condition, participants came to the
laboratory at 12.00 (after five hours of wakefulness).
They were kept indoors two hours before being photographed
to avoid the effects of exposure to sunlight and
the weather. We had a series of five or six photographs
(resolution 3872×2592 pixels) taken in a well lit room,
with a constant white balance (×900l; colour temperature
4200 K, Nikon D80; Nikon, Tokyo). The white
balance was differently set during the two days of the
study and affected seven photographs (four taken during
sleep deprivation and three during a normal night’s
sleep). Removing these participants from the analyses
did not affect the results. The distance from camera to
head was fixed, as was the focal length, within 14 mm
(between 44 and 58 mm). To ensure a fixed surface
area of each face on the photograph, the focal length
was adapted to the head size of each participant.
For the photo shoot, participants wore no makeup,
had their hair loose (combed backwards if long), underwent
similar cleaning or shaving procedures for both
conditions, and were instructed to “sit with a straight
back and look straight into the camera with a neutral,
relaxed facial expression.” Although the photographer
was not blinded to the sleep conditions, she followed a
highly standardised procedure during each photo
shoot, including minimal interaction with the participants.
A blinded rater chose the most typical photograph
from each series of photographs. This process
resulted in 46 photographs; two (one from each sleep
condition) of each of the 23 participants. This part of the
study took place between June and September 2007.
In October 2007 the photographs were presented at
a fixed interval of six seconds in a randomised order to
65 observers (mainly students at the Karolinska Institute,
mean age 30 (range 18-61) years, 40 women), who
were unaware of the conditions of the study. They
rated the faces for attractiveness (very unattractive to
very attractive), health (very sick to very healthy), and
tiredness (not at all tired to very tired) on a 100 mm
visual analogue scale. After every 23 photographs a
brief intermission was allowed, including a working
memory task lasting 23 seconds to prevent the faces
being memorised. To ensure that the observers were
not primed to tiredness when rating health and attractiveness
they rated the photographs for attractivenes
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