The eye-opening study was conducted by the Karolinska Institute, which asked 25 university students to take part.
The team, led by Dr. Tina Sundelin, asked 25 university students, who volunteered to participate in the experiment, to have two nights of flawless sleep in a row, before having their picture taken.
The Independent reports that those who looked at the participants' photos after only four hours of sleep, they thought they were less attractive, less healthy, less trustworthy and would not socialize with them.
"An unhealthy-looking face, whether due to sleep deprivation or otherwise, might activate disease-avoiding mechanisms in others", said Axelsson. They also considered the poorly rested subjects to be less attractive, less healthy and more sleepy compared to when they were well rested.
"Sleep deprivation is associated with a wide variety of physiological changes, such as impaired immune function, reduced cardiovascular health, and even impaired glucose metabolism", she says, which is why people who are sleep deprived can be viewed as less healthy.
Although previous research has shown 31 hours of wakefulness resulted in a less attractive appearance, in everyday life it is more common to experience partial sleep loss, she said.
Researchers found that people were less willing to socialise with tired-looking subjects.
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A group of 122 strangers then rated the photos on how much they wanted to socialise with them. However, Dr Sundelin also pointed out, "I don't want to worry people or make them lose sleep over these findings though".
You know the drill: You haven't had a good night's sleep for a few days and now you don't like what you see in the mirror - puffy eyelids, dark circles, sallow skin.
"People seem to be able to tell when someone needs more sleep, and are more inclined to leave them alone in that case", the authors wrote in the new work.
Not like we needed another excuse for a sleep in!
As for trustworthiness, the respondents displayed no difference in attitude, the study noted.
Still, the findings are interesting - if only as a reminder of the many ways that not getting enough sleep can negatively affect your wellbeing, including, apparently, your social wellbeing.