Sleeping well directly affects your mental and physical health. Getting more sleep seems to have several benefits: increased energy, emotional control, and an improved sense of well-being.
However, a new study complicates this picture, suggesting that more sleep isn’t necessarily sufficient to bring about those kinds of appealing improvements.
The study, co-authored by MIT economists, is a distinctive field experiment of low-income workers in Chennai, India. Scientists studied localized residents during their everyday routines. They managed to increase participants’ sleep by about half an hour per night, a very substantial gain.
It was found that sleeping more at night did not improve people’s work productivity, earnings, financial choices, sense of well-being, or even blood pressure. Instead, it lowers the number of hours they worked.
Frank Schilbach, an MIT economist, said, “To our surprise, these night-sleep interventions had no positive effects whatsoever on any of the outcomes we measured.”
Scientists also found that daytime naps are found to increase productivity and well-being. For another thing, participants tended to sleep at night in difficult circumstances, with many interruptions. The findings leave open the possibility that helping people sleep more soundly, rather than just adding to their total amount of low-grade sleep, could be useful.
Schilbach suggests, “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.”
The inspiration for this study came from a past study that suggested low-income people tend to have difficulty sleeping with their other daily challenges.
Schilbach said, “In Chennai, you can see people sleeping on their rickshaws. Often, four or five people are 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.”
During the study, participants were asked to keep actigraphs to monitor human rest/activity cycles. A total of 452 participants were examined over a month. Scientists used a different way to make participants sleep more. Those ways include encouragement, financial incentives, etc.
Some members of both those groups also took daytime naps to see what effect that had.
The participants in the study were also given data-entry jobs with flexible hours while the experiment was taking place. This allowed scientists to monitor the effects of sleep on worker output and earnings in a granular way.
Overall, the Chennai study’s participants averaged about 5.5 hours of sleep per night before the intervention and added 27 minutes of sleep per night on average. However, to gain those 27 minutes, the participants were in bed an extra 38 minutes per night. That speaks to the challenging sleep circumstances of the participants, who, on average, woke up 31 times per night.
Schilbach said, “A key thing that stands out is that people’s sleep efficiency is low; that is, their sleep is heavily fragmented. 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.”
“That could be why, across a wide range of metrics, people in the study experienced no positive changes after sleeping more. Indeed, 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.”
“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. These two interventions have different effects.”
“Naps only increased total income when compared to workers who took a break instead. Naps did not increase the total income of workers — nappers were more productive per minute worked but spent less time working.”
“It’s not the case that naps pay for themselves. People don’t stay longer in the office when they nap, presumably because they have other things to do, such as care for 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.”
- Pedro Bessone et al. The Economic Consequences of Increasing Sleep Among the Urban Poor. DOI: 10.1093/qje/qjab013