With commentary by Josiane Broussard, PhD, assistant research professor of integrative physiology, University of Colorado, Boulder.
Sleeping in on the weekends after skimping on sleep all week may seem indulgent, but it's also good for your health, new research suggests.
"If you can't sleep more during the week, you can improve your health by sleeping more on the weekend," she says. "Sleeping in is good for you."
With her colleagues, she found in a small study of 19 men that sleeping in for two nights in a row reversed the ill effect of too little sleep on the body's insulin sensitivity, the ability to regulate blood sugar levels.
Experts know that even short-term sleep restriction, getting just four or five hours a night, can boost the risk of getting type 2 diabetes by about 16 percent, she says. That risk increase is about equal to the risk of diabetes in those who are obese, according to the study researchers.
"We have substantial evidence now to tell us that sleep deprivation has harmful effects on metabolism, particularly the glucose metabolism," says Esra Tasali, MD, associate professor of medicine at the University of Chicago. She is the study's principal investigator and senior author.
What the researchers wanted to find out, Tasali says, is whether extending sleep after sleep-restricted nights can prevent people from becoming glucose-intolerant and insulin-resistant and from developing diabetes.
Findings from the study, published online in the journal Diabetes Care, suggest that it can.
The men, on average age 23, spent the nights in the sleep lab. For four nights, they were allowed in bed for 8.5 hours a night. The next 4, they were allowed in bed only 4.5 hours. After that, they were allowed 12 hours one night and 10 the next.
On average, they slept nearly 8 on the ''normal'' nights, 4.3 on the restricted nights and almost 10 on the recovery nights.
Throughout the study, the researchers evaluated insulin sensitivity. The men all ate standard meals before each testing period.
Overall, their insulin sensitivity declined by 23 percent after the sleep restriction, compared to normal sleep, and their risk of diabetes was estimated to increase by 16 percent. However, after the two recovery nights, the insulin sensitivity and risk of diabetes returned to what it was.
Although the findings are generally good news for those who find it difficult to get in enough sleep during the week, Tasali says it doesn't mean they shouldn't still try to get enough sleep every night. When that isn't possible, however, she says, the recovery sleep can be an alternative strategy.
Common wisdom has it that it's impossible to ''catch up'' on sleep, but Tasali says she is not aware of any definite study finding that scientifically. However, she says, doctors do typically tell patients not to try to catch up, but to sleep the same amount each night—not always possible, of course.
Because the study looked only at men in their 20s, the researchers can't say if the findings apply to women or older people or to those at high risk of diabetes. Some other research has found that in those who already have diabetes, both sleeping too much and sleeping too little can have ill effects on blood sugar levels.
Although the study is small, it does demonstrate that the recovery sleep ''can counteract the adverse effects of sleep restriction that causes insulin resistance in people," says Samuel Klein, MD, the William H. Danforth Professor of Medicine and Nutritional Science and Chief of Geriatrics and Nutritional Science at Washington University in St. Louis. He reviewed the findings.
"This is good news," he says of the study. "If you are losing sleep for whatever reason, you can catch up and improve your insulin sensitivity by getting two nights of [extra] rest."
However, he has an important caveat. Following this pattern every week, he says, won't mean you will remain as healthy as if you had never had sleep deprivation.
Another expert, Minisha Sood, MD, director of inpatient diabetes at Lenox Hill Hospital, New York, also calls the findings promising. But she warns that the findings are not generalizable to others beyond those studied.
1. Two Nights of Recovery Sleep Reverses the Effects of Short-term Sleep Restriction on Diabetes Risk. Diabetes Care. http://care.diabetesjournals.org/content/early/2015/12/17/dc15-2214.full.pdf+html. Accessed online January 18, 2016.
2. https://sleepfoundation.org/excessivesleepiness/content/sleep-longer-lower-blood-glucose-levels. Accessed online January 18, 2016.