This lack of rest has consequences. Evidence shows that sleeping less is associated with chronic diseases, mental illnesses and increased health care costs, among other problems, according to the Centers for Disease Control and Prevention.
Now, in a series of experiments, researchers have shown this deprivation may be detrimental not only to ourselves, but to others around us, by making us less generous. The paper was published last week in PLOS Biology.
“This is the first study to show unambiguously that sleep loss can reduce the tendency of individuals to help one another,” Russell Foster, director of the Sleep and Circadian Neuroscience Institute at the University of Oxford in England, who did not contribute to the research, tells the Guardian's Sascha Pare.
In one experiment, the researchers brought two dozen adults into their lab for two separate overnights, reports Science News' Sujata Gupta. Participants got a normal amount of sleep one night and were kept awake during the other.
The mornings after, each participant filled out a questionnaire in which they rated how likely they’d be to help people in various scenarios, such as giving up a seat to a stranger on a bus or giving a coworker a ride, per Science News. Over 75 percent of participants rated their desire to help others lower after the sleepless night, compared to the restful one. Tired participants indicated a lower likelihood to help family and friends as well as strangers, according to the Guardian.
The researchers also gave these participants brain scans and found that after the sleepless night, they had reduced activity in a region of the brain associated with social behavior, per the Guardian.
In another experiment, over 100 participants kept a sleep log for four nights and answered questions about helping people the next day, according to Science News. These participants self-reported their sleep and did not come into the lab. Again, the researchers found that the worse the participants slept, the less interested they were in helping others, per Science News.
Through these surveys, the researchers also noticed that quality of sleep had a greater effect on selfishness than purely the number of hours, writes CNN's Hafsa Khalil. “The findings could suggest that once sleep duration rises above some basic nominal amount, then it appears to be the quality of that sleep that is most critical for aiding and supporting our desire to help other people,” Eti Ben Simon, a neuroscientist and sleep researcher at the University of California, Berkeley, who led the research, tells CNN.
Finally, the researchers analyzed more than three million charitable donations made between 2001 and 2016. They found that donations dropped by about 10 percent after clocks were moved ahead for Daylight Savings Time, per CNN. "Even just an hour of sleep loss was more than enough to influence the choice to help another," Ben Simon tells CNN.
It’s possible, however, that some variable other than sleep caused the change in generosity, David Dickinson, a behavioral economist at Appalachian State University who did not contribute to the study, tells Science News. But since the researchers used several different methodologies, “this puts a more comprehensive story on how inefficient sleep affects decisions in this domain of helping others,” he tells the publication.
The researchers also say that a society struggling from a lack of sleep might face some broader consequences. “These findings have major implications across all levels of society but particularly for our night shift, frontline staff,” Foster tells the Guardian. “Doctors, nurses and the police are often chronically tired, and the findings suggest that their ability to help under difficult and demanding circumstances may be compromised.”