Many people debate about sleep quality versus quantity – which should we prioritize? A new MIT study reveals the answer. Eye-opening sleep research on the working poor in India found that sleep quality rather than quantity made a more significant impact on health.

According to the sleep study, getting more sleep didn’t alter work productivity or overall health for impoverished workers in India. However, naps or better quality sleep at night did produce positive results.

This counters the advice of modern scientists who tell us to get more shut-eye. It seems that five hours of high-quality sleep may have more benefits than eight hours of interrupted sleep. For people who almost have to pencil sleep into their schedules, this should come as welcome news. It certainly makes a difference for poor workers in India who can’t afford to sleep longer hours.

About the Study on Sleep Quality Versus Quantity

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Based on a field experiment of low-income workers in Chennai, India, the study yielded essential findings about sleep. For the experiment, researchers observed residents at home during their everyday routines. The scientists gave participants tips for better sleep, which seemed to pay off. On average, the participants slept about 30 extra minutes per night, a significant gain.

However, the researchers found no difference in the following metrics from increased sleep:

  • work productivity
  • earnings
  • financial choices
  • sense of well-being
  • blood pressure

In fact, sleeping more only cut into their work hours, resulting in lower pay.

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

The paper is titled “The Economic Consequences of Increasing Sleep Among the Urban Poor.” It’s been published in the August issue of The Quarterly Journal of Economics.

How poverty impacts sleep quality

The results seem counterintuitive; wouldn’t more sleep yield a better quality of life? Researchers say not necessarily.

Nighttime sleep quality and duration depend primarily on environmental and societal factors. For example, the participants living in Chennai dealt with many interruptions and challenges at night, leading to low-quality sleep. So, even if they slept longer hours, that didn’t mean they necessarily got deeper, better sleep.

However, they did find that daytime naps increased productivity and well-being, partially countering the adverse effects of poor nighttime sleep. The findings show that sleeping more soundly, regardless of hours slept, may significantly impact health.

“People’s sleep quality is so low in these circumstances in Chennai that adding sleep of poor quality may not have the benefits that another half hour of sleep would have if it’s of higher quality,” Schilbach suggests.

Schilbach, a development economist, says the study builds on previous research he and his colleagues have done in areas like Chennai. In these settings, the researchers found that low-income people often live in regions inconducive to sleep. Compounded with other daily challenges, this makes it challenging to get restful sleep at night.

“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.”

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The study on sleep quality versus quantity

For the study, researchers gave the participants actigraphs or wristwatches to track sleep states from body movements. This gave the team access to critical data while the participants slept. Most sleep studies occur in labs, so this experiment offered unique insight on sleep quality versus quantity.

The study observed 452 people over the course of a month. Researchers offered some participants encouragement and tips for improved sleep. Others received financial incentives to sleep longer hours. In addition, some members from both groups took daytime naps to see how they impacted their sleep.

Finally, the participants took data-entry jobs with flexible hours for the duration of the study. This made it easier for researchers to track the effects of sleep on worker output and income.

On average, the study participants slept about 5.5 hours per night before the study. During the study, they slept about 27 extra minutes per night. However, the participants stayed in bed an extra 38 minutes a night to gain additional sleep. This observation reveals how difficult it is for Chennai residents to sleep soundly at night. Sadly, they woke up about 31 times per night on average due to noise, bugs, or other disturbances.

“A key thing that stands out is that people’s sleep efficiency is low, that is, their sleep is heavily fragmented,” Schilbach says. “They have extremely few periods experiencing what’s thought to be the restorative benefits of deep sleep. People’s sleep quantity went up due to the interventions, because they spent more time in bed, but their sleep quality was unchanged.”

This explains why most people in the study didn’t benefit from sleeping longer.

Schilbach added, “We find one negative effect, which is on hours worked. If you spend more time in bed, then you have less time for other things in your life.”

Naps help but cut into earnings for low-income workers

Researchers found that the participants who took naps had improved markers in several areas.

“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.”

However, the naps only led to higher income when compared to workers who took a break instead. Workers didn’t actually earn more due to the naps; they had increased productivity but spent less time working.

“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.”

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Final Thought: Everyone can benefit from better sleep quality (versus quantity)

Schilbach says he hopes the study on sleep quality versus quantity will lead to further research in the future. For instance, changing the sleeping environment of low-income workers could yield different results. Perhaps their sleep quality, not just quantity, would improve if their circumstances changed.

The economist added that it’s important to consider how psychological factors impact sleep quality in low-income people. Schilbach says the following:

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

He says that using wristwatches that track sleep quality will change the scope of studies in the future. This allows researchers more flexibility since they can observe people in their everyday lives rather than just a laboratory.

“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.”

“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.”

In conclusion, the study on sleep quality versus quantity shows how poverty creates even more obstacles to a good night’s sleep. However, everyone deserves and needs restful sleep.  Hopefully, further research will help those who live in poverty improve their sleep quality and overall well-being.