MIT sleep study yields unexpectedly surprising results


[Nov 25, 2022: Peter Dizikes, MIT]

Sleeping more seems to be a big advantage. (Credit: Creative Commons)

Getting more sleep in particular has great benefits: many people find that it gives them more energy, emotional control and a better sense of health. But a new study co-authored by MIT economists complicates the picture, suggesting that getting more sleep alone isn’t enough to drive these kinds of lucrative improvements.

The study is based on a specific field experiment with low-income workers in Chennai, India, where researchers studied residents at home going about their normal daily routines – and managed to increase participants’ sleep by about half an hour a night, a very important advantage. And yet more sleep at night didn’t improve people’s work productivity, earnings, financial choices, sense of well-being, or even their blood pressure. Apparently the only thing was that they reduced the number of working hours.

Frank Schilbach, MIT economist and co-author of a new paper detailing the study’s findings, says, “To our surprise, these nighttime sleep interventions had no positive effect on the outcomes we measured. “

There’s more to it: First, researchers found that short naps during the day help with productivity and well-being. In addition, the participants tried to sleep through the night under difficult conditions, with multiple interruptions. The findings leave open the possibility that it could be useful in helping people sleep more soundly, rather than adding to their total amount of low-quality sleep.

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“The quality of sleep people have in these conditions in Chennai is so poor that adding poor quality sleep does not bring the benefits associated with half an hour of sleep,” Schilbach suggests.

The article, “Economic consequences of increasing sleepiness among the urban poor,” is published in Quarterly magazine Economy, The authors of the article are Pedro Besson PhD ’21, a recent graduate of MIT’s Department of Economics; Gautam Rao, associate professor of economics at Harvard University; Shilbach, Gary Loveman Career Development Associate Professor of Economics at MIT; Heather Schofield, assistant professor at the Perelman School of Medicine and the Wharton School at the University of Pennsylvania; and Matti Toma, an economics doctoral student at Harvard University.

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sleep on rickshaw

Shilbach, a development economist, says the genesis of the study stems from other research he and his colleagues have done in environments such as Chennai – in which they found low-income people have trouble sleeping in addition to their other daily tasks. Challenges.

An experiment with the working poor in India shows that quality is more important than quantity when it comes to sleep. (Credit: Creative Commons)

“In Chennai, you see people sleeping on their rickshaws,” says Schilbach, who is also a faculty member at MIT’s Abdul Latif Jameel Poverty Action Lab (J-PAL). “Four or five people often sleep in the same room where there is noise and noise, you see people sleeping in the middle of road sections next to the highway. It is also incredibly hot at night and there are a lot of mosquitoes. Essentially, you can find every possible irritating or detrimental sleep factor in Chennai.

The figure provides an overview of the timeline and experimental design of the study. (Credit: Quarterly Journal of Economics)

To conduct the study, the researchers equipped Chennai residents with actigraphs, wristwatch-like devices that derive sleep status from body movements, allowing the team to study people in their homes. Many other sleep studies look at people in lab settings.

The study examined 452 people for one month. Some received encouragement and tips to sleep better; Others found financial incentives to sleep more. Some members of both groups also took naps during the day to see what effect it had.

The figure shows the mean of sleep-related variables for the different treatment groups in the RCT study. All results are actigraph measurements. (Credit: Quarterly Journal of Economics)

Study participants were also given data entry jobs with flexible hours during the experiment, so researchers could closely monitor the effects of sleep on workers’ output and earnings.

Overall, before the intervention, the Chennai study participants averaged about 5.5 hours of sleep per night, adding an average of 27 minutes of sleep per night. However, to gain those 27 minutes, the participants spent an additional 38 minutes each night in bed. This speaks to the challenging sleeping conditions of the participants, who woke up an average of 31 times per night.

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“One important thing is that people have poor sleep efficiency, that is, their sleep is too fragmented,” says Schilbach. “They don’t have enough time to think about the restorative benefits of deep sleep. … The interventions increased the amount of sleep people got because they spent more time in bed, but there was no change in the quality of their sleep.” ”

That’s why, across a wide range of metrics, study participants experienced no positive changes after getting more sleep. According to Schilbach, “We even found a negative effect, namely on working hours. If you spend more time in bed, you have less time for other things in your life.”

On the other hand, study participants who were allowed to nap while entering data did better in several measured categories.

“Unlike nighttime sleep interventions, we found clear evidence of improvements in a range of outcomes, including their productivity, their cognitive function and their psychological well-being, as well as some evidence on savings,” says Schilbach. “These two interventions have different effects.”

That said, naps only led to higher total earnings compared to employees taking breaks instead. Naps did not increase workers’ total income — workers were more productive per minute of nap, but spent less time actually working.

“It’s not like the nap just pays for itself,” says Schilbach. “People don’t last very long in the office when they take a nap, possibly because they have other things to do, like taking care of their families. When people sleep for about half an hour, their working time drops by about half an hour, almost one-to-one, and as a result, people in that group earn less.

Value sleep as an end in itself

Schilbach says he hopes other researchers will answer some of the study’s more questions. For example, further work could try changing the sleep conditions of low-income workers to see if improved sleep quality, not just more sleep quantity, makes a difference.

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Schilbach also suggests that it may be important to better understand the psychological challenges of the poor when it comes to sleep.

“Being poor is very stressful and it can disrupt people’s sleep,” he notes. “How environmental and psychological factors affect sleep quality is worth investigating.”

Schilbach notes that using actigraph technology and other devices, it should be possible to increase the number of studies that record people’s sleep patterns in their normal home environments, not just medical ones.

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

For his part, Schilbach says he’s interested in continuing the work on sleep that’s happening in America, not just India, where he’s done most of his research. In any setting, he says, we need to take the issue of sleep seriously as part of poverty reduction research and public policy — and as an important part of well-being in its own right.

“Sleep can be just as important as a pathway to better productivity or other kinds of choices,” says Schilbach. “But I think that a good night’s sleep is also important in itself. We should consider it important to be able to sleep well and not be anxious at night. Poverty indices are about income and material consumption. But now that we can better measure sleep, getting a good night’s sleep should be part of a more comprehensive measure of people’s well-being. I hope we get there eventually.

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Note: Above content provided by MIT. The content can be edited for style and length.

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