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Surprising MIT study challenges conventional wisdom about sleep

[June 25, 2023: Staff Writer, The Brighter Side of News]

Getting more sleep seems to provide big benefits. (CREDIT: Creative Commons)

While many people report experiencing increased energy, emotional stability, and a greater sense of well-being when they get more sleep, a recent study co-authored by MIT economists challenges this assumption. The study, which was conducted in Chennai, India, involved a unique field experiment that examined the impact of increased sleep on low-income workers.

Despite managing to increase participants' nightly sleep by half an hour, the study found that this increase did not lead to improvements in their work productivity, earnings, financial decision-making, overall well-being, or blood pressure. The only noticeable effect was a reduction in the number of hours worked.


The study was conducted by observing the daily routines of participants in their homes, making it a unique and valuable field experiment. Despite the significant increase in sleep time, the researchers found that this increase was not enough to bring about the positive effects typically associated with getting more sleep. Rather, the results indicate that more sleep alone is not sufficient to bring about improvements in work productivity, financial decision-making, or overall well-being.

Frank Schilbach, an MIT economist and co-author of a recent study, stated, “To our surprise, these night-sleep interventions had no positive effects whatsoever on any of the outcomes we measured”.


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However, the research also discovered that taking short daytime naps can enhance productivity and well-being. Additionally, due to challenging situations, participants had disrupted sleep at night. The study indicates that assisting individuals in achieving a better quality of sleep rather than just increasing their total amount of poor-quality sleep could be beneficial.

Schilbach suggests that in Chennai, where people’s sleep quality is significantly low, the benefits of adding poor-quality sleep may not be as effective as adding another half hour of higher-quality sleep.


A paper titled "The Economic Consequences of Increasing Sleep Among the Urban Poor" has been published in The Quarterly Journal of Economics. The authors of the paper include Pedro Bessone, who recently graduated from MIT’s Department of Economics with a PhD; Gautam Rao, an associate professor of economics at Harvard University; Schilbach, the Gary Loveman Career Development Associate Professor of Economics at MIT; Heather Schofield, an assistant professor in the Perelman School of Medicine and the Wharton School at the University of Pennsylvania; and Mattie Toma, a PhD candidate in economics at Harvard University.'

An experiment with working poor in India finds when it comes to sleep, quality may matter more than quantity. (CREDIT: Creative Commons)

Sleeping on rickshaws

Schilbach, a development economist, explains that the idea for the study originated from prior research he conducted with his team in locations like Chennai. In their investigations, they observed that individuals with limited financial resources frequently encounter obstacles when attempting to get adequate sleep. This issue exacerbates the challenges these individuals already face on a daily basis.


“In Chennai, you can see people sleeping on their rickshaws,” says Schilbach, who is also a faculty affiliate at MIT’s Abdul Latif Jameel Poverty Action Lab (J-PAL). “Often, there are four or five people sleeping in the same room where it’s loud and noisy, you see people sleep in between road segments next to a highway. It’s incredibly hot even at night, and there are lots of mosquitos. Essentially, in Chennai, you can find any potential irritant or adverse sleep factor.”

This figure presents an overview of the timeline and experimental design of the study. (CREDIT: The Quarterly Journal of Economics)

The researchers utilized actigraphs, which are wristwatch-like devices that determine sleep states from body movements, to conduct their study on Chennai residents. This approach enabled the team to observe individuals in their natural home environments, unlike many other sleep studies that observe participants in laboratory settings.


During the study, 452 individuals were observed for a period of one month. The participants were divided into two groups; one group was provided with encouragement and sleep improvement tips, while the other group received financial incentives to increase their sleep duration. Additionally, some members from both groups were allowed to take daytime naps, which were monitored to determine their impact on sleep quality.

This figure shows the average of different sleep-related variables for different treatment arms by day in study of the RCT. All outcomes are actigraph measures. (CREDIT: The Quarterly Journal of Economics)

Moreover, to analyze the impact of sleep on worker productivity and earnings, the participants were assigned flexible data-entry jobs during the course of the study. This allowed the researchers to closely examine the relationship between sleep and work performance on a detailed level.


Overall, the Chennai study, the average nightly sleep duration of participants prior to the intervention was around 5.5 hours. After the intervention, the participants experienced an increase in sleep duration by an average of 27 minutes per night. However, to achieve this increase, the participants spent an additional 38 minutes in bed per night. The participants' sleep was further hampered by their fragmented sleep patterns, with an average of 31 wake-ups per night.

According to Schilbach, one of the study's researchers, a noteworthy finding is the low sleep efficiency among participants, with very few periods of deep sleep, which is essential for restorative benefits. Despite spending more time in bed due to the intervention, the participants' sleep quality remained unchanged, and the increase in sleep quantity was mainly due to the additional time spent in bed.

Individuals did not experience any significant improvements despite sleeping more, based on various metrics, according to the researchers. Instead, they encountered a negative effect on their working hours, as Schilbach pointed out. If they spent more time sleeping, they had less time for other aspects of their life.

On the contrary, those study participants who were given permission to nap during their data-entry job performed better in several measured categories.


“In contrast to the night sleep intervention, we find clear evidence of naps improving a range of outcomes, including their productivity, their cognitive function, and their psychological well-being, as well as some evidence on savings,” Schilbach says. “These two interventions have different effects.”

On one hand, naps were found to have a positive effect on the overall income of workers who took a break. However, it should be noted that nappers tended to be more productive per minute worked but spent less time on actual work, which did not lead to an increase in their total income.

“It’s not the case that naps just pay for themselves,” Schilbach says. “People don’t actually stay longer in the office when they nap, presumably because they have other things to do, such as taking care of their families. If people nap for about half an hour, their hours worked falls by almost half an hour, almost a one-to-one ratio, and as a result, people’s earnings in that group are lower.”

Valuing sleep as an end in itself

Schilbach expresses his desire for other researchers to delve into the other issues that have been raised by the study. To determine whether improved sleep quality, in addition to increased sleep quantity, has an effect, further research could seek to modify the sleeping conditions of low-wage workers.


Schilbach suggests that understanding the psychological challenges that poor people face when it comes to sleep is crucial.

“Being poor is very stressful, and that might interfere with people’s sleep,” he notes. “Addressing how environmental and psychological factors affect sleep quality is something worth examining.”

Moreover, Schilbach suggests that by utilizing actigraph technology and other devices, researchers can conduct more studies that observe people's sleep patterns in their natural homes instead of just medical facilities.

“There’s not a lot of work studying people’s sleep in their everyday lives,” Schilbach says. “And I really hope people will study sleep more in developing countries and poor countries, focusing on outcomes that people value.”

Schilbach would really like to further his sleep research in the United States, in addition to the extensive research he has conducted in India. He emphasizes the significance of sleep as an essential component of anti-poverty research and public policy, as well as a vital aspect of overall well-being, irrespective of the setting.


“Sleep might be important as an avenue for improved productivity or other types of choices people make,” Schilbach says. “But I think a good night’s sleep is also important in and of itself. We should value being able to afford to sleep well and not be worried at night. Poverty indices are about income and material consumption. But now that we can measure sleep better, a good night’s sleep should be part of a more comprehensive measure of people’s well-being. I hope that’s where we’re going eventually.”

For more science news stories check out our New Discoveries section at The Brighter Side of News.


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