The health risks of losing sleep are well known, ranging from heart disease to depression, but who knew that too little sleep can also make you selfish?
That's the takeaway of new research from the University of California, Berkeley.
"This new work demonstrates that a lack of sleep not only damages the health of an individual, but degrades social interactions between individuals and, furthermore, degrades the very fabric of human society itself," said Matthew Walker, director of the university's Center for Human Sleep Science. "How we operate as a social species — and we are a social species — seems profoundly dependent on how much sleep we are getting.”
Walker and co-author Eti Ben Simon, a postdoctoral fellow in psychology, noted that a growing number of studies, including this one, show that sleep loss compromises bonds between individuals — and even the altruistic behavior of nations.
“If you're not getting enough sleep, it doesn't just hurt your own well-being, it hurts the well-being of your entire social circle, including strangers,” Ben Simon said.
In a research review published online Aug. 23 in PLOS Biology, the researchers described three separate studies that gauged the impact of sleep on people's willingness to help others.
In one, 24 healthy volunteers underwent brain scans after eight hours of sleep and also after a sleepless night. The functional MRI scan revealed that brain areas involved in empathy and trying to understand others' wants and needs were less active after a sleepless night.
“When we think about other people, this [theory of mind] network engages and allows us to comprehend what other person's needs are: What are they thinking about? Are they in pain? Do they need help?” Ben Simon said. “However, this network was markedly impaired when individuals were sleep deprived. It's as though these parts of the brain fail to respond when we are trying to interact with other people after not getting enough sleep.”
Another study tracked more than 100 people online for three or four nights, measuring how long they slept and how many times they woke. Then it gauged their desire to hold an elevator door open for someone else or help an injured stranger on the street, among other scenarios.
“Here, we found that a decrease in the quality of someone's sleep from one night to the next predicted a significant decrease in the desire to help other people from one subsequent day to the next,” Ben Simon said. “Those with poor sleep the night prior were the ones that reported being less willing and keen to help others the following day.”
And, finally, a database of 3 million charitable donations in the United States between 2001 and 2016 showed giving dropped after the seasonal change to Daylight Saving Time. Donations fell 10% overall, but not in regions where the time doesn't shift, the study authors reported.
“Even a very modest ‘dose' of sleep deprivation — here, just the loss of one single hour of sleep opportunity linked to Daylight Saving Time — has a very measurable and very real impact on people's generosity and, therefore, how we function as a connected society,” Walker said. “When people lose one hour of sleep, there's a clear hit on our innate human kindness and our motivation to help other people in need.”
In an earlier study, Walker and Ben Simon found that sleep deprivation increased feelings of loneliness, caused people to isolate and, when they did interact with people, to spread their loneliness to others.
“Looking at the big picture, we're starting to see that a lack of sleep results in a quite asocial and, from a helping perspective, anti-social individual, which has manifold consequences to how we live together as a social species,” Walker said. “A lack of sleep makes people less empathetic, less generous, more socially withdrawn, and it's infectious — there is contagion of loneliness.”
Promoting sleep rather than shaming people for getting enough sleep could help shape social bonds, Ben Simon suggested. More than half of people in developed countries report not getting enough sleep.
“In these divisive times, if there was ever a need for a strong, prosocial lubricant to enable the very best version of ourselves within society, now seems to be it,” Walker said. “Sleep may be a wonderful ingredient that enables the alacrity of helping between human beings.”
The World Sleep Society has a free magazine with information about healthy sleep and tips on getting your Zzzs.
SOURCE: University of California, Berkeley, news release, Aug. 23, 2022