Waking up from a nap or a good night’s sleep is a refreshing feeling. You feel well rested and recharged. Sleep and mood are intimately connected, which is why you often feel happier when you are well rested. There are days when you feel the opposite, you may even feel more tired after a long nap. Understanding sleep patterns and how your brain operates in terms of sleep can help explain the tiredness and ways to resolve it.
What happens between sleep and wakefulness?
Your brain is an intricately designed organ and works 24/7. The brain also takes up the responsibility of protecting itself. Do you ask yourself, why do I feel groggy when I wake up? Feeling groggy and “slow” after you have just woken up is called sleep inertia . This feeling can last between 15-30 minutes but can also last up to 90 mins depending on other sleep issues. Sleep inertia might even happen after a long nap or getting a good night’s rest. If you work shifts, where your sleeping patterns keep changing, you might also experience sleep inertia. It is predicted that this is a protective mechanism to allow the body to go back to sleep if the brain is insufficiently rested . It could also possibly be to protect the brain while it transitions from one state (sleep) to another (wakefulness) .
Why does your brain need extra time to wake up?
Your sleep is organised in 4 stages in your brain. These stages make up 1 sleep cycle. Read more here. The third stage is the deepest sleep stage where your brain is hard at work. If awoken in the middle of this stage, you feel groggy .
Housekeeping is one of jobs the brain does during sleep where it clears out end products of chemical reactions. When a drowsiness inducing chemical is yet to be cleared out, and you wake up before this happens, you might feel groggy . The active compound in tea and coffee, caffeine, helps to remove this chemical, which is why coffee helps you perk up after a sleepless night .
How does sleep inertia impact cognitive performance?
If you try to solve maths quizzes and do intense mental work soon after you wake up, you are likely to underperform. Sleep studies found that cognitive performance like decision making, memory skills and calculations is 51% lower immediately after waking up . It can take up to 30 minutes to boost 30% of your performance . One possible reason is that the blood flow to the brain is slower during the first 30 mins of waking up . Got an intense project to work on? Save it for mid-morning when your brain is ready to seize the day.
How much sleep do you need to wake up refreshed?
Good quality sleep is irreplaceable, and 7 hours of nightly sleep is best for cognitive performance .
So how much sleep do we need when napping? The Sleep Foundation recommends 20 minutes to boost alertness . Sleeping for too long might lead you to wake up in the middle of your sleep cycle, thus disrupting sleep. Long naps can also lead to staying awake for longer at night and thus add to disturbed sleep.
3 ways to manage sleep inertia and wake up better.
There are ways to shorten the time you feel groggy and jumpstart your day:
- Caffeine can be your friend: Caffeine found in tea and coffee is a stimulant because it counteracts the drowsiness chemical in the brain. Those who took caffeine immediately after a long 2 hour nap, had a quicker resolution of sleep inertia . A 100mg caffeine gum improved cognitive function within 5 mins of waking up, which was 15 mins faster than the de-caffeinated group . Due to caffeine’s stimulating effect, avoid taking it later during the day to promote good sleep.
- Turn on the lights: Bright light promotes wakefulness by decreasing sleep hormone, melatonin. Just 1 min of bright light exposure (2000 lux- unit of brightness) after a 20 mins nap can improve alertness within 1 hour . It can also help improve mood, which can contribute to alleviating grogginess .
- Regulate work and sleep time: Avoid scheduling the most intense mental work soon after you wake up to give your brain enough time to prep for the day. Shorter naps during the day (20 mins) and 7 hours of sleep, to complete sleep cycles can have beneficial effects in waking up refreshed every day.
Being patient with your brain as it recovers after your sleep is recommended. Sleep inertia is a normal phenomenon and, in most cases, harmless. Simple and effective strategies can help reduce the feeling of grogginess to give you a refreshing start to your day.
- Sleep Foundation. (2021). Sleep Inertia: Causes, Symptoms, and Treatment.
- Hilditch, C. J et al. (2019). Sleep inertia: current insights. Nature and science of sleep, 11, 155–165
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- Tai, X.Y. et al. (2022). Impact of sleep duration on executive function and brain structure. Communications Biology.
- Hilditch, C. J. et al. (2016). Time to wake up: reactive countermeasures to sleep inertia. Industrial health, 54(6), 528–541.
- Hilditch, C.J. et al. (2022). Rise and shine: The use of polychromatic short‐wavelength‐enriched light to mitigate sleep inertia at night following awakening from slow‐wave sleep. Journal of Sleep Research.