Adults should sleep seven to nine hours per night. This is recommended by professional societies such as the US National Sleep Foundation. Those who rest less not only risk being tired and exhausted the next day: the risk of various diseases such as cardiovascular diseases and diabetes also increases if the night's rest is permanently too short. A team from the University of California at Berkeley led by Eti Ben Simon has discovered another side effect of lack of sleep: apparently, people behave less helpful to others after a short night, as the group reported in the journal "PLOS Biology".
Ben Simon and colleagues examined the connection between helpfulness and lack of sleep in a total of three studies. In one of them they asked 136 men and women to run a sleeping diary for four days. They also asked the test subjects every morning how helpful they would be that day. Did you go into a woman on the way to work, who obviously struggled with her many shopping bags, would you take the time and offer a helping hand? And what about the work colleague who has just missed his bus on the way home: do you take a piece with it? If the participants had slept less or worse in one day than before, they were less common for such actions, as the evaluation of the data showed.
According to a significantly more extensive data analysis, the willingness to help could not only influence the willingness to help in such hypothetical situations: for their second study, the researchers evaluated more than three million donations that between 2001 and 2016 in the days before and after the changeover to summer time in the United States had been made. When switching to summer time, the clocks are presented an hour every year in March - which leads to most people to one hour less sleep. Studies know that the body takes a few days to get used to the time change in spring.
Here the researchers were also able to find that people were less freely greedy in the days after the time change and were less donated. In contrast, however, this pattern in spring was not evident in states without a time change. Even when changing from summer to winter, the phenomenon could not be observed. These are all indications that the effect could actually be related to the shorter bedtime.
A wakeful night is accompanied by a change in brain activity
But why does a sleep deficit apparently let us act less socially? The third experiment that the California research group carried out could provide answers to this question. In addition, the scientists ordered 24 healthy young adults in the sleep laboratory and let them sleep for one night while they kept them awake for another night. After waking up night, the test subjects, as in the other attempts, were less willing to help someone. This was also evident in her brain: As examinations in the brain scanner revealed, the areas that help to anticipate the thoughts and feelings of others were less active after a night without sleep.
"It's as if these parts of the brain don't react when we try to interact with other people after getting too little sleep," explains Ben Simon. Study author Matthew Walker sees it in a similar way: sleep is apparently a kind of lubricant for prosocial, empathic, kind and generous human behavior.
