It's Friday and you're clocking off, and after a few sleepless nights you want to tuck yourself up early and catch up on all the sleep you've lost. But does it really work that way?
During sleep our memories from the day are solidified and our brain does a bit of a clean-up sorting through the things we need to hold onto and discard from the day. We also get the rest we need to ensure we can function properly the following day.
But not all of us manage to get eight hours sleep per night, and might miss out on some of these benefits. So we asked five experts if it's possible to catch up on missed sleep later.
Chin Moi Chow, sleep researcher
We can catch up on sleep but not on the exact number of hours lost. Catching up on sleep is essential, since sleep is a biological necessity. The body has only one way of dealing with lost sleep. With acute sleep loss, sleep pressure increases and we cannot resist sleep. We dive into a long, deep sleep when a sleep opportunity arises (such as extended sleep on weekends).
In this recovery, we make up deep sleep. But we have lost the opportunity to transform unstable memories into the more stable form. And a single extended sleep episode is not sufficient for a full recovery from chronic sleep loss. Intrusive microsleep episodes or daytime napping often occur when the need is pressing.
The consequences of chronic sleep deprivation are severe, including decreased performance, gastrointestinal disorders, and increased risk of obesity, diabetes and heart disease – death being the ultimate consequence.
Leonie Kirszenblat, neuroscientist
Yes, in the short term. If you have a bad night's sleep you will feel like you need to sleep more the following night. This is because the brain detects when we haven't had enough sleep, through the accummulation of 'sleep pressure'. Sleep pressure causes physiological changes to the brain, to tell your brain when it needs to sleep more.
Although you can catch up on a bit of lost sleep, being chronically sleep deprived is bad for the brain. This is because sleep rewires connections between your brain cells, helping you to consolidate important memories, and forget things that are probably less important. So catching up on sleep on the weekend is unlikely to help you remember things you learnt earlier in the week.
Sleep also helps to flush out toxic proteins linked to neurodegenerative disorders. That's why consistently getting enough sleep is better for learning and maintaining a healthy brain in the long term.
Siobhan Banks, sleep researcher
We are physiologically driven to get sleep when we go without. The pressure for sleep builds while we're awake until, finally if we haven't slept for many days, we will fall asleep anyway – even standing up. The world record for the longest time awake is 11 days, and the young man who reached this recorded caught up on his lost sleep by sleeping 14 hours in one go.
But our ability to 'catch-up' depends on how chronically sleep deprived we are. If you have been accumulating a sleep debt for some time it can be harder to catch up. You may need many nights of good quality sleep to catch-up and we know that can be difficult. If you chronically don't get enough sleep or it's of poor quality (for example, when you have a sleep disorder like sleep apnoea), it could take many days of good sleep to wake up feeling refreshed.
Gemma Paech, sleep researcher
While we may be able to sleep for longer periods of time following sleep loss, for example sleeping in on the weekends, we can never recover lost sleep hour for hour. Rather, following sleep loss, sleep becomes deeper, which can help our alertness and functioning return to normal.
The bad news though, is that sleep loss can accumulate over time, affecting our overall health and well-being. The long term effects of a repeated sleep restriction/recovery schedule are unknown. Sleeping in on weekends may also affect our circadian timing system, resulting in what we call "social jet lag". It can be possible to reduce the effects of sleep loss by extending sleep, or "banking sleep", prior to a period of sleep loss. But the best way to avoid the adverse effects of sleep loss is to get consistently adequate sleep across the week.
Melinda Jackson, psychologist
If we try and sleep for longer the next day to make up for lost sleep, we will impact our rhythms in the next cycle. Our sleep-wake cycle is based on a 24-hour rhythm; once we move into the next cycle our biological clocks essentially 'reset'. For example, if we are sleep restricted during the working week, and then compensate for this by sleeping in on the weekend, we might find it hard to fall asleep at our usual bed time on Sunday evening.
It's best to keep a regular sleep and wake schedule, as our brains have an inbuilt compensatory mechanism for sleep loss and will adjust the intensity of sleep depending on our need.