Good night's sleep key to beauty: Swedish study
Vivian Tse · 16 Dec 2010, 12:00
Published: 16 Dec 2010 12:00 GMT+01:00
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"My daughter once asked me, 'Why is Sleeping Beauty so beautiful? Is it because she slept?' As a scientist, when I say something, it has to be the truth, it has to be backed up," he told The Local on Thursday.
"However, science also has to be fun. It's our responsibility to make science fun. So many beliefs about things affect our entire culture. Many of these beliefs are untrue, but this seems to be true across different cultures," Axelsson added.
The Karolinska team investigated the relationship between sleep and perceptions of attractiveness and health. Twenty-three participants aged 18 to 31 took part in the study, which was carried out three years ago. The results were published by the British Medical Journal online on Monday.
"We did not control for attractiveness, only for illnesses and sleep disturbances. We wanted to look at sleep," said Axelsson.
Participants were photographed from 2pm to 3pm on two occasions, once after a normal night of sleep and once after an entire night deprived of sleep. Smokers were excluded from the research and no alcohol was allowed for two days prior to the experiment.
"Smoke affects the skin, making one look less attractive, while alcohol disturbs sleep and affects muscle tone," Axelsson explained.
Half of the group started with a full night's sleep, while the other half started sleep-deprived, then underwent the second half of the experiment two weeks later.
The full night's sleep involved seven to nine hours of slumber the night before the photographs were taken. Participants had to lay in bed for at least eight of those hours.
The photographs were taken seven hours after the participants woke up.
For the sleep-deprived photographs, the participants were kept awake for 31 hours straight.
The photographs of just the subject's faces were taken in a well lit room and the distance to the camera was fixed. During both photography sessions, participants wore no make-up, had their hair loose or combed back for long hair and underwent similar cleaning or shaving procedures.
They were asked to have a relaxed, neutral facial expression for both photos.
Sixty-five observers rated the photographs for attractiveness and whether the individuals looked healthy and tired/not tired.
The observers judged the faces of the sleep-deprived participants as less healthy, less attractive and more tired.
The researchers concluded that the facial signals of sleep-deprived people affect facial appearance and judgments of attractiveness, health and tiredness.
Axelsson recommends seven to eight hours of sleep a night for most adults and strongly advises against sleeping less than six hours a night on a regular basis.
"One can manage five-hour nights one to two nights in a row, but it is very hard to perform as well the next day. It can also lead to immune activations, worse metabolisms and pre-diabetic conditions," he cautioned.
As for those who sleep too much, Axelsson said that it can be a sign of disease, when one needs more sleep, or chronic inflammation.
Axelsson and his colleagues are currently at work on a paper evaluating the results of extended sleep disturbances.
"The entire field of sleep focusses on metabolism, brain and cognitive functions. There is less data on how it affects us socially and our relationships. There are lots of anecdotal examples of people looking worse, but no scientific evidence," he said.