The Social Power of Sleep
Sleep isn’t just good for your health — it’s good for society
Physical exhaustion and diminished concentration are familiar to everyone, but sleep deprivation may impact social behavior too. Sociality isn’t just important for meeting people and making friends; it underlies many of the most revered activities in modern society, from voting in elections to helping people in need. The study of sleep may therefore give a fresh perspective on the best and worst instincts of humanity.
In U.S. surveys covering over 300,000 adults between 1985 and 2012, the number of adults sleeping six hours or less increased by 31%, with the most dramatic changes occurring before 2004. Six hours’ shut-eye isn’t enough. The National Sleep Foundation, after evaluating all available evidence with a panel of experts in 2015, recommended seven to nine hours of sleep per night for adults to maintain optimal health and functioning.
Sleep deprivation also impacts the human body more globally, with links to physical health issues such as obesity and high blood pressure. General sleep disturbances, reflecting both too much sleep and too little sleep outside of the seven to eight hour range, could even be associated with an earlier death.
On the whole, it’s easy to find research on how poor sleep quality disturbs people’s biology, burdens cognitive performance, and perturbs brain activity. But it’s only recently, in March 2019, that one group of researchers from the U.S. and Germany published research examining what these outcomes may mean for the common good.
One critical civic duty in modern society is the duty to vote in elections. Healthy democracies depend on the input of large, diverse, and representative samples of citizens who participate in electing leaders to act in their interests. Higher voter turnout is considered a sign of social engagement, shared values, and societal cohesion.
The researchers analyzed data from national surveys that included questions on voting behaviors and sleep quality. They statistically removed the effects of variables that include age, gender, income, and education, and tested the remaining relationship between how much people reported sleeping and how likely they were to vote. According to their analysis, poor sleep quality consistently predicted lower voter turnout.
The researchers went a step further by exploiting a natural sleep variation that exists within the U.S. People who live immediately east of a time zone border get an average of 20 to 25 minutes less sleep per night than people who live immediately west of that border. This is because the time difference introduces a sudden change in daylight hours: The eastern side of the border tends to go to bed later than the western side because the sun sets an hour later according to their clocks. Unfortunately, morning routines never adjust to account for the sun’s schedule, so easterners still start work at 9 a.m. even if they went to bed later than their western compatriots.
If the researchers’ theory is correct, people living on the eastern edge of a time zone border should vote less than people living on the western edge, after accounting for other differences between those populations. To test this, the researchers first confirmed that easterners did indeed get less sleep on average than westerners, and then analyzed voter data to check whether overall turnout patterns supported their predictions. As they expected, people living east of the border were generally less likely to vote than similar people living west of the border.
Next, the researchers split their data according to the proportion of African Americans living in each area, which is a surrogate measure for levels of poverty and hardship. Among the socioeconomically disadvantaged communities, time zone-related sleep loss was almost three times more influential in reducing voter turnout, which reinforces the idea that sleep deprivation really does have social consequences. It also resonates with prior evidence suggesting that economic deprivation and social fragmentation are linked to worse sleep quality among children living in poor neighborhoods.
It’s worth noting that sleep disturbances don’t impact everything people do with their day. When the researchers tested the connection between time zone-based sleep measures and typical daily activities, they found nothing significant for tasks such as watching television, cleaning, or using a computer.
The experiments above hint at a relationship between sleep and voting behavior, but cannot say much about whether sleep deprivation directly causes a drop in prosocial actions. For that, the researchers conducted one final experiment, and this time, they also expanded their prosocial measures beyond voting.
Overall, compared to those who completed the experiment during the sociable afternoon hours, the sleep-deprived people were five percentage points less likely to be civically engaged.
Using an online service known as Amazon Mechanical Turk, they sent out a survey to over 1,000 people that measured basic demographics, sleeping habits, and political interests. Then, they asked everyone to return for a second survey, which would test their willingness to engage with particular prosocial activities. Some people were randomly selected to return between 2 and 4 p.m., while others were told to return during the insomniac hours of 3 and 5 a.m.
The people who completed the second survey during the night were significantly less likely to sign a petition encouraging community recycling, and were generally less inclined to donate money to the Red Cross, or vote in an upcoming election. Overall, compared to those who completed the experiment during the sociable afternoon hours, the sleep-deprived people were five percentage points less likely to be civically engaged. And once again, the data patterns suggested that socioeconomically disadvantaged people were most affected, but subgroup samples were too small for a conclusive analysis.
The research outcomes above are the first to connect sleep quality and civic engagement, but they build on existing evidence that demonstrates emotional harm from sleep loss.
For example, in research from 2015, scientists studied brain areas that distinguish between threatening and non-threatening expressions on other people’s faces (e.g. the dorsal anterior cingulate cortex and anterior insula). After a night of sleep deprivation, those brain areas lost their threat-related sensitivity, and people started to see faces as more menacing. Some of the same faces they believed to be non-threatening after a night of sleep were judged as threatening after a night of wakefulness.
In another experiment, when adolescents were restricted to four hours of sleep for two consecutive nights, their negative emotions surged during social interactions the next day. The researchers also measured pupil dilation, which is a physiological signal commonly linked to mental effort and arousal. When the adolescents heard unpleasant emotional sounds, their pupils dilated more aggressively than the pupils of adolescents who were not sleep-deprived.
A 2015 scientific review concluded that sleep deprivation impaired people’s ability to recognize emotions in others, and increased their emotional reactivity. This higher reactivity was potentially caused by disrupted communication between the amygdala (a brain center involved in emotional responses) and the prefrontal cortex (a brain center involved in regulating amygdala activity).
During the day following a sleepless night, many people are understandably concerned about their personal health and productivity. The science is now showing that sleep also has a social side, and that group activities and civic well-being may deserve the same attention as personal well-being. Adding to the challenge, sleep quality and social engagement are in a mutual tug of war: A bad night’s sleep contributes to social disconnect, and social disconnect contributes to a bad night’s sleep. It’s important to resist these vicious cycles by taking care of bedtime habits and avoiding late-night activities that delay sleep onset.
There is already a push within the public health sector to improve sleep quality and prevent some of the medical risks associated with sleep deprivation. With evidence that social cohesion is also part of the equation, and that vulnerable citizens suffer most from sleep disturbances, communities may be justified in pushing with a little more urgency. The national demand for societal harmony provides just another incentive for people to look after their recommended seven hours of shut-eye.