We all know someone who can't help but pour themselves a long black or a cappuccino at 4 pm — no matter the impact on sleep quality.
Whether you join them, gawk or nestle into the peppermint teas, it's worth considering the ins and outs of caffeine and sleep and what is considered safe when it comes to caffeine consumption.
So how does caffeine affect sleep, and what can you do about it? We've done all the hard work for you (we even wrote this with a coffee in hand) — so let's dive into it.
What is caffeine?
Most often consumed in beverages, caffeine is a natural psychoactive substance widely used across the world.
Found in a bunch of different plants, including coffee beans, tea leaves, cacao pods and kola nuts, caffeine can also be synthetically produced and popped into medications and energy drinks [1].
Caffeine is absorbed into the bloodstream about 45 minutes after consumption, and you are likely to experience the peak anywhere between 15 minutes to 2 hours afterwards.
Caffeine from beverages like tea, coffee and soda is quickly absorbed into the gut as it dissolves in both the body's water and fat molecules [1].
Broken down mostly in the liver, caffeine can remain in your blood anywhere from 1h30 to 9h30 fter consumption [2].
So now you know exactly what caffeine is, let's look into how it affects the brain.
How does caffeine affect the brain?
When consuming caffeine, your stomach and small intestine quickly absorb it. After it's absorbed, it will be distributed throughout your entire body as it crosses the blood-brain barrier.
Inside your brain, caffeine blocks adenosine receptors, which are sleep-promoting chemicals that are produced in your brain during waking hours [1].
Generally, adenosine builds up in your brain the longer you're awake, and the more it builds up, the more sleepy you become. When you consume caffeine, it blocks this process and keeps you alert. So, what are the sleep-disrupting effects of caffeine?
How does caffeine affect sleep?
Well, now we know how the brain is affected by caffeine, it's obvious that sleep can be greatly impacted too.
First things first, caffeine can influence sleep duration, sleep efficiency and sleep satisfaction. It can reduce the time of slow-wave sleep, which is the stage of deep and restful sleep that leaves us feeling refreshed and alert when we wake up.
Caffeine-interrupted sleep can also lead to sleep deprivation the next day, which you can feel by the way of fatigue and problems with learning, memory, problem-solving, and emotional regulation [1].
A study found that even caffeine consumed 6 hours before bed could reduce sleep time by 1 hour — so if you have trouble dozing off, you might want to remember this!
Research shows that the caffeine effects go one step further in interfering with your circadian melatonin rhythms. Circadian rhythms are physiological patterns that operate on a 24-hour clock [2]. They're held in check by the external cycle of day and night, as well as by an internal cellular process.
The buildup of adenosine contributes to the circadian rhythm, and caffeine can interfere with this process in a big way.
How much caffeine is safe to drink?
There's no hard or fast rule about how much caffeine is safe to drink as every person is different, but in general, it's important to find a level of consumption that's safe for you.
The Food and Drug Administration (FDA) recommends the average safe daily caffeine consumption sits at around 400mg or 4-5 cups of coffee per day — but for some folk, this would send you spiralling!
It's also important to note that every time you consume it, it's likely to have a different caffeine content (unless you know exactly where you're getting your caffeine from and it's the same measured standard every time).
For example, an average large cup of coffee can have up to 470mg of caffeine, which is more than the average daily recommendation [2]. For some, consuming this much caffeine might be breezy and for others, it could throw your sleep completely out of whack.
If you're unsure about how much caffeine is safe to consume for your body weight and metabolism, it's best to check in with a doctor.
Can caffeine keep you awake?
As caffeine causes a burst of energy in your body, it stimulates the central nervous system [3].
While most people drink coffee in the morning to wake them up, caffeine consumed at night time can cause a lot of harm for some people.
Although it boosts cognitive performance in fatigued folk, it can't replace a good night of sleep or fix the long-term effects of sleep deprivation.
Studies also show that the effectiveness of caffeine completely varies depending on the dose and the state of the individual. As an example, caffeine might benefit a person who feels tired, but for someone who feels alert and aroused, it may cause anxiety, restlessness and caffeine dependency.
Can caffeine cause insomnia?
There are short-term performance benefits to your morning cup of coffee, but overusing caffeine can actually lead to insomnia symptoms or worsen acute and chronic insomnia [3].
Consuming caffeine to stay awake at night time can lead to sleeplessness, anxiety and poorer sleep quality.
Caffeine in soft drinks has actually been linked to increased severity of sleep-disordered breathing, which is a primary factor of obstructive sleep apnoea. It's important to note that this was found only within caffeine from soft drinks, and not from tea or coffee beans.
How many hours before bedtime should you stop having caffeine?
While this is different for everyone, the recommended cut-off time for caffeine use is a minimum of 6 hours before bedtime. This means that if you go to bed at 9 pm, you should avoid drinking coffee or having caffeine after 3 pm.
This can help minimise sleep disturbances as well as the quality of sleep you get. You might even find that you sleep better with a longer period of caffeine abstinence before bedtime.
How can I tell if caffeine is affecting my sleep?
If you regularly consume caffeine and you also don't sleep well (or you're regularly having a daytime recovery sleep after a poor night of sleep), you might want to consider reducing your caffeine intake.
Otherwise, if you're experiencing insomnia, headaches or anxiety during the day, this can sometimes be a sign of caffeine overuse or caffeine dependence [3].
You might also experience troubles during the night including frequent awakening, inability to fall asleep, and nighttime anxiety.
Do you experience excessive daytime sleepiness but coffee doesn't help? You might be sleep-deprived from long-term caffeine use. If that's the case, you might find it helpful to put down the coffee for a while and see how it affects your sleep.
What are common caffeine withdrawal symptoms?
Just as caffeine impacts everyone differently, the symptoms of caffeine withdrawal can vary.
In saying this, the general symptoms include things like headaches, fatigue, drowsiness, dysphoric mood and irritability, difficulty concentrating and even flu-like symptoms including vomiting, muscle pain or stiffness [3].
How to sleep after consuming too much caffeine
If you've had a busy day and overloaded yourself with coffee, you might find you have difficulty falling asleep. There are some great ways to ease your mind, reduce the effects of caffeine and improve sleep quality [4].
Turn off your electronics
Caffeine increases alertness and stimulates your brain, and so does your phone, the TV and social media. They prevent your brain from relaxing, so your best bet is to switch them off at least an hour before bedtime.
Meditate
If you're trying to fall asleep after consuming caffeine, you might like to try mindfulness or meditation. Sit or lie down in a comfortable position and take deep but unforced breaths.
While it can be tricky to silence your mind, the aim of the game is not to shut off your thoughts. Simply watching your breath can create a calmer environment for your nervous system to help you fall asleep.
Take a brief walk
If you've had too much caffeine, taking a short walk before bedtime can be a great way to wind your body and mind down to fall asleep. It might even force some of the extra caffeine out of your body.
Read a book in bed
Reading is a brilliant way to de-stimulate your mind, reduce stress and even induce tired eyes.
Tried all of the above and still have no luck falling asleep? You might find Pilot's sleep support super helpful in nipping sleeplessness in the bud. Simply take our online quiz and an Aussie practitioner will review your answers and recommend treatment.
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