REST ASSURED
I’m a sleep expert and a simple calculation can stop you waking up groggy
IN an ideal world, you’d wake up to your alarm feeling refreshed and ready for the day every single morning.
And a sleep expert has revealed how you can avoid that groggy morning feeling with a simple sleep calculation.
1
It’s backed by various experts and often called the “90-minute rule”.
The method is based on hacking your sleep cycles.
When you sleep, you go through several sleep cycles in one night.
They are comprised of:
- Stage 1 (N1): The dozing off stage, lasting one to five minutes.
- Stage 2 (N2): Body relaxes into a light sleep, lasting 10-25 minutes.
- Stage 3 (N3): Deep sleep, the most important for restoration, lasting 20-40 minutes
- Stage 4: REM (rapid eye movement) sleep, when dreams occur, lasting 10-60 minutes.
If your alarm goes off halfway through deep sleep or REM sleep, when dreaming and memory storing happens, you’ll likely feel groggy.
Everybody has had the experience of being forced awake mid-dream and desperately wanting to go back to sleep - even if just to “finish the dream”.
Waking up during N3 (deep sleep) would also feel disorentating.
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But if you wake up naturally, at the end of your 90 minute cycle, you’ll feel refreshed.
Even if you have had less sleep than you would have liked, waking up at the end of a cycle will feel much better than mid-way through it.
Alison Gardiner, behavioural psychologist and the founder of NHS-backed sleep programme Sleepstation, told : “At the end of each sleep cycle we all become fully alert for a short time.
“Most people won’t remember waking up, but we all do.
"It's ideal to wake up at the end of a sleep cycle and to have cycled through at least four to five sleep cycles over the course of the night.
"When you are in stage N1 sleep, you can be wakened easily. If you are awakened, you will probably claim not to have been asleep as we’re often not consciously aware of this stage of sleep.
"However, if you're woken from the deeper sleep states – further into a sleep cycle – you'll be consciously aware that you've been woken from sleep and you can experience a groggy, disorientated feeling.
"When we wake at different times each day, or are woken up unexpectedly, we're more likely to feel groggy in the morning.
“This feeling is called sleep inertia and it can last for the first few hours of the day.”
The symptoms of sleep inertia include a desire to go back to sleep, impaired cognitive ability and grogginess.
The calculation
Each sleep cycle lasts approximately 90 minutes, and we tend to go through four to six cycles a night.
The best way to make sure you wake at the end of a cycle is to work back from when you want to get up to get your ideal bedtime.
If you need to wake up at 7am, you should count backwards in 90 minute cycles.
Then add on around 15 minutes - the time it takes to get to sleep.
You’ll be looking at hitting the sack at either 9.45pm for nine hours sleep, or 11.15pm for seven and a half hours sleep.
You could still go to bed between 9.45pm and 11.15pm, but risk being rudely awakened by your alarm mid-cycle.
Use this to work out your bedtime.
Alison said you don’t need to be too strict with sticking to the 90-minute cycles.
"While the average sleep cycle lasts around 90 minutes, each person is different and it would require a lot of effort to discover the length of your sleep cycles and then to work to optimise them," she said.
“Sleep problems can start when people become over-focussed on their sleep – and try to control it.
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“So if your sleep isn't broken, it would be best to leave well alone.
"If you're feeling well rested and alert during the day then you're probably getting the right amount of sleep for your needs and there would be no need to try to control your sleep cycles in order to further optimise your sleep."
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