Ben Simon E, Vallat R, Rossi A, Walker MP. Sleep loss leads to the withdrawal of human helping across individuals, groups, and large-scale societies. PLoS Biol. 2022;20(8):e3001733.
To determine whether night-to-night variations in sleep quality or duration affect the desire to help others
People who sleep well are kinder. Not sleeping well diminishes people’s ability to be kind.
The investigation consisted of 3 separate studies that included:
- a crossover, interventional trial
- a longitudinal study
- an epidemiological study
Study 1 recruited 24 healthy participants (aged 18–26 years, 54% female). Investigators excluded individuals whose recent activities may have disrupted their sleep/wake cycles (eg, recent travel between time zones).
Study 2 recruited 136 individuals who then self-reported their sleep duration and sleep quality and also completed questionnaires to assess their desire to help others. Accelerometer watches tracked their sleep, and investigators analyzed the data for the 4-day study period.
Study 3 amassed data from over 3 million charitable donations made between the years 2001 to 2016 in the United States and examined the impact shifts to daylight savings time had on donation amounts.
In Study 1, the participants took part in a counterbalanced, crossover experiment with 2 conditions: 1 night of good sleep contrasted with a night of no sleep, and these conditions were separated by 7 days. After each condition (sleep or no sleep), participants completed standardized helping questionnaires between 9 a.m. and556tyrghbv 867786 11 a.m.; they also performed a social cognition task during a functional magnetic resonance imaging (fMRI) scan at around 10 a.m.
Study 2 was a microlongitudinal design protocol in which participants completed helping questionnaires and sleep diaries for 4 consecutive days under free-living conditions.
Study 3 assessed large-scale altruistic donation behaviors (https://www.donorschoose.org/) during transitions to daylight savings time (DST).
These 3 studies dovetailed together to provide an expanding measure of the effects sleep disruption has on a specific aspect of social function. Study 1 involved controlled sleep manipulations (sleep vs no sleep), while Study 2 examined changes in sleep quality and duration under free-living conditions. Study 3 looked for a measurable impact on social behavior.
Study 1: The first study demonstrated that at an individual level, 1 night of sleep deprivation triggers the withdrawal of the desire to help another individual, both strangers as well as family. The fMRI findings revealed that the withdrawal of human helping is associated with deactivation of key nodes within the social cognition brain network that facilitates pro-sociality.
Study 2: Data from the second study showed that worse sleep efficiency from night to night was associated with next-day decreases in the desire to help others. Reduced helping was further evident across individuals, such that worse sleep efficiency overall was associated with a diminished desire to help others. These effects were significant and independent of changes in sleep quantity, and they remained significant when accounting for trait empathy scores and daily changes in mood. Such findings suggest that poor sleep, either across individuals or relative to one’s own habitual sleep profile, significantly and robustly reduces prosocial helping.
Study 3: The data analyzed in Study 3 showed, as the researchers had hypothesized, that the transition to DST was associated with a significant decrease in altruistic decisions to give away money compared to the weeks either before or after the transition. For reference, the size of the sleep effect represents approximately a 10% reduction in donation amounts given.
Taken together, these 3 studies establish that insufficient sleep (both in quantity or quality) acts as a degrading force that influences whether humans wish to help one another. This creates a measurable impact, reducing the tendency for them to do so. Investigators observed the effects of poor sleep at 3 different levels of the social scale: within the individual, between individuals, and at a nationwide level.
These findings seem obvious and predictable and should come as no surprise. We already assume that someone who hasn’t slept long enough or well enough will exhibit social behaviors that might be summed up as “cranky.” Ask any parent. While this study specifically looked at 1 trait, generosity, we might assume that other synonymous social traits will also be negatively impacted. Simply put, poor sleep makes it harder to be kind.
The Centers for Disease Control and Prevention (CDC) recommends that adults get 7 to 8 hours of good sleep each night.1 Yet a 2016 CDC report suggests that one-third of US adults get less than this.2 In the US, 70% of adults report “that they obtain insufficient sleep at least 1 night a month, and 11% report insufficient sleep every night.3
In a 2008 report, approximately 29% of US adults reported sleeping less than 7 hours per night, and 50 million to 70 million had chronic sleep and wakefulness disorders. Data from 2006, collected as part of the CDC’s Behavioral Risk Factor Surveillance System, showed that slightly more than 10% of adults received insufficient rest or sleep on all of the preceding 30 days.3
Many assume that there is something of an epidemic of poor sleep that has gotten worse over time. Yet in a 2015 paper by Youngstedt et al, UCLA researchers challenged the assumption that we are increasingly sleep-deprived. After reviewing data from the last 50 years, they reported finding little evidence that people ever really slept more than they do now and “have challenged the notion of a modern epidemic of insufficient sleep.”4
In other words, while lots of people are now having trouble getting an adequate night’s sleep, this may not be any worse than it was in years past.
We do know that poor sleep is associated with poor health. It may increase the likelihood of developing dementia, heart disease, type 2 diabetes, obesity, and cancers of the breast, colon, ovaries, and prostate.5 Poor sleep also affects the ability to function while performing daily tasks like working or driving.
Sleep deprivation doesn’t just leave people less generous and kind—it leaves them meaner. And sicker.
It’s not just generosity that takes a hit from sleep deprivation. One recent study, in which young adults (mean age 20.8 years, N=23) were kept awake, “found that acute sleep deprivation, limited to a 24-hour period, increases negative emotion states such as anxiety, fatigue, confusion, and depression. Sleep deprivation results in increased inflammation and decreased cortisol levels in the morning and are accompanied by deficits in vigilance and impulsivity. Combined, these results suggest that individuals who undergo 24 hours of sleep deprivation will induce systemic alterations to inflammation and endocrine functioning, while concomitantly increasing negative emotions.”6
Sleep deprivation doesn’t just leave people less generous and kind—it leaves them meaner. And sicker.
A recently published study reports that poor sleep is associated with a significantly increased risk of cardiovascular disease (CVD). Analysis of data from 7,850 study participants showed that “sleep problems were associated with 75% increased risk of CVD (OR: 1.75; 95% CI 1.41, 2.16), more than double the risk of congestive heart failure (CHF) (OR: 2.28; 95% CI 1.69, 3.09), a 44% increase in risk for coronary heart disease (CHD) (OR: 1.44; 95% CI 1.12, 1.85). Risk of angina or heart attack both approximately doubled [angina pectoris (OR: 1.96; 95% CI 1.40, 2.74), and heart attack (OR: 2.05; 95% CI 1.67, 2.53) and 78% ].”7
To be sure, associations do not prove causation. Perhaps those with CVD simply don’t sleep as well in the first place because of the impending disease. The long-term effects of chronic sleep deprivation cannot be proven through the usual means, a randomized clinical trial.
Clearly, poor sleep is bad for our individual health. This study by Ben Simon et al suggests that poor sleep impacts society and the social networks we live in. As the authors note in their paper’s introduction, “Humans help each other. Helping is a prominent feature of homo sapiens.”
This is a human quality, the magnitude of which we may not fully appreciate. In 2019 charitable giving amounted to about $450 billion in the United States and 10 billion pounds in the United Kingdom (for 2017–2018). About half of people in the United States, Europe, and Asia report donating to charity or helping a stranger each month.8
The willingness to help other humans appears built into our psyches and has been researched and debated at length as to its origins and purpose. Some assume it to be the result of evolutionary forces9 as well as something we learn as members of a society. Neuroscientists can now identify the regions of the brain that comprise the social cognition network that regulates empathy and the desire to provide compassionate help. This study demonstrated that sleep deprivation acutely affects this region, reducing generosity.
Many people strive to go through life sleeping less, as if it were a mark of ability or competence. Some even seem to brag about how little sleep they “need,” as if their sleep debt was a good thing.
We need to question patients about their sleep. But my other thought after reading this study is how to incorporate the specific association between poor sleep and lower generosity into clinical practice. This certainly gives us one more symptom of poor sleep to add to our symptom list. Yet patients never come to us with a chief complaint of “feeling less generous.” We probably aren’t going to add a question about charitable giving to our intake forms. Patients can display varying levels of “kindness” or sociability in their interactions with you or your office staff during their visit. Rather than just charting that a patient is “gruff or grumpy,” we might consider that such behaviors might signal our need to investigate sleep behaviors more closely.
What this study does suggest is that our efforts to counter unhealthy sleep habits and help individual patients sleep better may have a multiplier effect, not only improving their own health but also perhaps increasing their inherent tendency to be generous; and this increase in generosity may benefit other people as well, particularly those in need.