The research, published in Current Biology, crushes those hopes. Despite complete freedom to sleep in and nap during a weekend recovery period, participants in a sleep laboratory who were limited to five hours of sleep on weekdays gained nearly three pounds over two weeks and experienced metabolic disruption that would increase their risk for diabetes over the long term. While weekend recovery sleep had some benefits after a single week of insufficient sleep, those gains were wiped out when people plunged right back into their same sleep-deprived schedule the next Monday.
“If there are benefits of catch-up sleep, they’re gone when you go back to your routine. It’s very short-lived,” said Kenneth Wright, director of the sleep and chronobiology laboratory at the University of Colorado at Boulder, who oversaw the work. “These health effects are long-term. It’s kind of like smoking once was — people would smoke and wouldn’t see an immediate effect on their health, but people will say now that smoking is not a healthy lifestyle choice. I think sleep is in the early phase of where smoking used to be.”
Clifford Saper, head of neurology at Beth Israel Deaconess Medical Center, called the study “convincing and fascinating.”
Michael Grandner, director of the sleep and health research program at the University of Arizona College of Medicine, said the study reinforces that people need to stop thinking of sleep as a balance sheet. Imagine a person who ate nothing but cheeseburgers and french fries, Monday through Friday, but dined only on celery and kale on the weekends and tried to call that a healthy diet, he said. Drastically cutting calories all week and then bingeing on a giant pizza on Saturday wouldn’t restore equilibrium, either. That, he argued, is essentially what people are doing when they skip sleep on weekdays with the idea they can make up for it on the weekend.
“When you’re talking about something as complex as metabolism, it’s very much about balance and equilibrium, and when you’re chasing numbers of hours and you’re trying to make them all add up, that’s not about balance,” Grandner said.
Wright said that the study suggests people should prioritize sleep — cutting out the optional “sleep stealers” such as watching television shows or spending time on electronic devices. Even when people don’t have a choice about losing sleep due to child-care responsibilities or job schedules, they should think about prioritizing sleep in the same way they would a healthy diet or exercise.
As for understanding the long-term effects of short weekday sleep and long weekend bouts, it will be important to extend the research beyond the artificial conditions and short time frame of a laboratory experiment. The researchers also found an intriguing gender difference, in which women got less recovery sleep on the weekends, and also were able to restrain their eating behavior better than men on the weekends — but experienced the same metabolic dysfunction, as measured by impairments in how their body responded to blood sugar.
"These were incredibly healthy people, with no medical problems, no psychiatric disorders, no drug use, no medications, no sleep problems, nothing at all — so when we put them on these types of schedules, they have the best possible outcomes, they have the lowest risk of any adverse health outcome as far as we can tell,” Wright said.