I think most of us intuitively know that we don’t look our best after a sleepless night or two. But we may not realize just how easy it is for others to detect our sleep-deprived state.
For according to a new study from the Karolinska Institute in Stockholm, Sweden, people can correctly identify from photographs alone if someone is sleep-deprived by using only a handful of cues: red and swollen eyes, hanging eyelids, dark circles under the eyes, droopy corners of the mouth, and pale, lined skin.
OK, OK. This may seem like a duh! study. But, as its authors note, no one had previously identified the precise facial cues that signal lack of sleep to others.
Furthermore, the fact that we can so easily tell if someone is sleep-deprived has social ramifications.
In previous research, the same scientists reported that sleep-deprived people are seen by others as being more fatigued, less attractive and even less healthy.
“The face serves a key role in social perception,” write the study’s authors, “affecting people’s judgments of everything from trustworthiness and aggressiveness to competence and likability in as little as 100 [milliseconds].”
Looking sleep-deprived, therefore, may not only affect a person’s personal relationships, but also their professional ones — and without anyone really being conscious of what’s going on.
For the study, the researchers photographed 10 men and women, aged 19 to 32, after an eight-hour sleep and again when they had been awake for 31 hours. All sorts of precautions were taken to make sure the conditions were similar for each photo shoot. Both photos were taken at 2:30 p.m., for example, and the volunteers groomed themselves similarly each time (such as same beard growth for men). The volunteers were also instructed to look at the camera with a neutral expression.
Forty people, aged 18 to 40, were then asked to rate the photos on 10 facial cues (dark circles under the eyes, red eyes, glazed eyes, hanging eyelids, swollen eyelids, pale skin, wrinkles/fine lines, rash/eczema, corners of the mouth pointing down, tense lips) and two other aspects associated with those cues (fatigue and sadness). The cues had been narrowed down from a longer list derived from a survey of 50 students and 10 sleep researchers.
The study found that seven of the 10 people were judged to look significantly more fatigued when sleep deprived than after a normal night’s rest. The facial cue that was the clearest giveaway was hanging eyelids, followed by swollen eyes, dark circles under the eyes, pale skin, fine lines and wrinkles around the eyes, droopy corners of the mouth and red eyes.
In addition, seven of the 10 people were judged to look significantly sadder when sleep deprived — probably because of the droopier mouths, say the study’s authors.
Glazed eyes, a skin rash and tense lips were not significantly associated with helping the participants correctly identify the sleep-deprivation photographs.
The eyes have it
The study confirms other research that shows humans look to the eyes to determine if someone is sleepy. But “whereas those studies focus on aspects of eye movements, such as blinking or eyelid closure, we demonstrate here that static information is also of importance,” write the study’s authors.
More surprisingly, perhaps, is the finding that skin appearance also played a significant role in determining fatigue.
“The role of sleep in the appearance and function of the skin has received remarkably little attention, despite the fact that the skin is the largest organ of the body and there is a strong increase in skin blood flow during sleep,” write the authors. “The function of this increase is unknown, but has been suggested to support the barrier defense of the skin as part of the immune system. Such a role for sleep in maintenance of the integrity of the skin is supported by the observation that skin lesions are among the first and most pronounced deficits in rats subjected to prolonged sleep deprivation. Also, endothelial dysfunction has been found in patients with obstructive sleep apnea. The mechanisms by which sleep deprivation causes pale skin, wrinkles, and dark circles under the eyes remain to be explored.”
This study, like all studies, had several limitations. Most notably, it involved only Caucasian Swedes. “Future studies should elucidate whether these findings can be generalized to other ethnicities and cultures,” write the study’s authors.
In addition, the study was small. Still, its findings are interesting and suggest that all of us should probably be paying more attention to that adage about “getting your beauty sleep.”
First, though, we’ll have to get rid of our stress and anxiety.
The study was published in the September issue of the journal Sleep.