It is understood that sleep is essential for long-term health, but up until now there has not been any scientific evidence as to how badly a lack of sleep affects the way we are perceived by others. Is there justification for the phrase ‘beauty sleep’? Did Sleeping Beauty know what she was about? Scientists in Stockholm determined to find out.
They had a serious aim though. Being able to get clues as to a patient’s health by looking at their face is helpful to a doctor, as Joseph Bell once explained.
‘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 health state.’ 
Joseph Bell was one of Sir Arthur Conan Doyle’s medical teachers and Conan used him as a model for the detective Sherlock Holmes. So, how many clues could doctors pick up about a patient’s health by looking at their face? And how could lack of sleep affect the degree of health or ill health that a patient projects? The researchers set out to discover the answers with the help of some bloodhounds and a violin. No, actually, just a sleep laboratory and some volunteers. 
Untrained observers were asked to rate the levels of perceived health and attractiveness of volunteers photographed after a normal night’s sleep and then after a night of sleep problems. The volunteers didn’t smoke, had no pre-existing sleep disorder, and hadn’t consumed alcohol within two days of the experiment. They were photographed after two hours indoors to avoid any influence of the weather and sunlight. The normal night’s sleep lasted on average 8 hours, and the restricted night provided the volunteers with 5 hours sleep and then 31 hours without sleep.
The researchers thought that humans are likely to pick up clues from the faces of other humans, as being able to gauge another’s emotional state, potential mate value, etc., would probably promote survival. The observers were not told which photographs were with or without sleep, but managed to pick up the clues every time. They rated the sleepless volunteers as being 6% less healthy, 4% less attractive, and 19% more tired. Considering that this was after just one night of sleep deprivation, the ability of humans to read the effects of restricted sleep in others’ faces is clearly well-tuned.
So it seems that the Prince probably fell for Sleeping Beauty because she had had more than her fair share of shut-eye and was therefore looking her sleep-enhanced best. Let’s hope they didn’t have children, as her face would very likely look rather different after a few months of baby-related sleep deprivation.
 Deten A et al. Cardiovasc Res 2005; 65: 52-63
 Axelsson J et al. BMJ 2010; 341:c6614 doi: 1Q1136/bmj.c6614