Why A Little Extra Sleep Can Help — Without Turning The Weekend Into A Time Zone Shift

After a poor night's sleep, the temptation to recover by staying in bed for several extra hours can be strong. For people who regularly sleep less than they need during the week, the weekend can become an opportunity to make up some of that lost rest.

Research suggests that recovery sleep can provide benefits after periods of insufficient sleep. But the evidence also indicates that there may be a limit to how useful a large weekend lie-in is, particularly when it substantially changes a person's usual sleeping schedule.

Sleep is regulated by two important processes: the build-up of sleep pressure while we are awake and the body's circadian rhythm, which responds to environmental signals including light and changes in daily routines.

Sleeping considerably later than usual can reduce sleep pressure later in the day and potentially make it harder to fall asleep at the usual time. A large shift in sleeping patterns can therefore leave someone struggling to get enough sleep again when the working week begins.

"It's like shifting time zones every single week," says Melynda Casement, a sleep psychologist and director of the University of Oregon Sleep Lab.

What Recovery Sleep Can Do

Controlled experiments have provided evidence that additional sleep can help the body recover from some effects of sleep restriction.

In one study, participants who slept for only two hours in a night experienced changes in levels of two types of white blood cells. Those who were subsequently given the opportunity to sleep for up to 10 hours showed levels that had nearly returned to their starting point.

Another experiment restricted 11 men, who normally slept for about eight hours, to four hours of sleep for six nights. The restriction affected measures of glucose clearance and insulin response. After participants were given six nights with a 12-hour sleep opportunity, those measures returned to baseline.

Other laboratory research has also found that recovery sleep following an all-nighter can restore aspects of cognitive performance.

These findings do not establish that catch-up sleep can undo all the effects of prolonged sleep deprivation. Some abilities, including sustained attention and spatial orientation, may remain impaired even after people have had opportunities to recover sleep.

Naps may also provide benefits for people who are short on sleep, although research into daytime naps and overnight recovery sleep has generally examined them as separate approaches.

The Evidence From Everyday Sleep Patterns

Research outside the laboratory presents a more complicated picture.

A Swedish study that followed more than 40,000 adults for 13 years found that, among people under 65, those who usually slept six to seven hours a night had the lowest observed mortality risk. People reporting five hours or less had a 65% higher mortality risk. The study also reported that weekend catch-up sleep appeared to remove the additional mortality risk among those short sleepers.

Other observational studies have reported associations between weekend recovery sleep and lower risks of conditions including high blood pressure, dementia and metabolic syndrome. However, the findings are not consistent across all research.

A large UK study, for example, found no association between weekend catch-up sleep and mortality or cardiovascular disease. It also did not find that sleeping in at weekends was associated with greater risk.

Because many of these studies observe people's existing sleeping habits rather than assigning them to different sleep schedules, they cannot by themselves establish that weekend lie-ins cause better or worse health outcomes.

How Much Extra Sleep Is Enough?

Research cited in the source material points towards roughly one to two additional hours of sleep as a potentially useful range for people recovering from insufficient sleep.

Studies in the US and South Korea have associated this amount of weekend recovery sleep with a lower risk of depression. Other research has linked additional sleep with lower inflammation among habitual short sleepers, while findings in younger people have suggested associations with lower risks of anxiety and depression.

Till Roenneberg, professor emeritus of chronobiology at LMU Munich's Institute for Medical Psychology in Germany, argues that people should not be overly rigid about maintaining exactly the same wake-up time every day.

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"Of course you have to catch up on sleep," he says. "Sleep is one of the most important functions in our lives."

There is, however, an important qualification for people with insomnia. The treatment approach described in the source material advises against responding to a poor night's sleep by going to bed earlier or sleeping in, because changing the established sleep schedule can make the problem more difficult to manage.

For most people, the research suggests that some recovery sleep after a bad night can be useful. The challenge is finding a balance: getting enough additional rest without shifting the sleep schedule so dramatically that the next night's sleep — and the return to the weekday routine — becomes harder.