Sleep is an essential function that allows the brain and body to rest and recharge. However, new study findings published in The Quarterly Journal of Economics show that simply getting more zzz’s is not enough if the quality of sleep is not good, reports

Over a one-month period, researchers from the Massachusetts Institute of Technology (MIT) monitored 452 low-income workers in Chennai, India, while they slept at home. (Scientists created a data entry job specifically to check their performance at work.)

Researchers outfitted the volunteers with wearable sensors called actigraphs that calculated the amount of sleep they got each night. In addition, scientists offered the workers support, tips and financial motivation to get better sleep. Some participants also napped during the day so researchers could see how these short periods of rest affected them.

Results showed that the interventions netted individuals nearly 30 minutes of additional shuteye each night on average. However, these participants woke up an average of 31 times due to hot weather, mosquitoes and overcrowded or inappropriate sleep environment, conditions that affect many of the world’s poor people.

After researchers evaluated the participants’ cognition, productivity, decision-making skills and overall well-being, they were surprised to learn that the night-sleep interventions had no positive effects on any of these measurable factors.

“A key thing that stands out is that people’s sleep efficiency is low, that is, their sleep is heavily fragmented,” said Frank Schilbach, PhD, an economist at MIT, who coauthored the study. “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.”

Interestingly, participants who snoozed for a half hour during the day experienced improved productivity, cognitive function and mental well-being.

Schilbach would like to see more studies comparing the quality of sleep versus the amount of sleep, especially among people facing stress and living in poverty.

To learn more about the connection between sleep and socioeconomic status, read "Poor People and People of Color Are More Likely to Get Insufficient Sleep."