Caffeine and Sleep: A restless relationship

A hot cup of joe. Lava java. Go juice. Or the simple cuppa’. Whatever you call it, as a country we seem to agree that we love coffee. With over 95 million cups brewed and consumed every day in the UK, we are absolutely addicted. And worldwide, caffeine is the most commonly used psychoactive stimulant. So it’s no wonder that coffee - and the caffeine inside it - is causing many of us to have a bad night's sleep, even if we’re unaware of how much damage it can do to our sleep.

Many people consider coffee an essential part of their morning routine, helping to shake off the cobwebs of sleep and to take on the day. When you’re awake, a chemical called adenosine continuously builds up in your brain and binds to receptors. The more adenosine there is, the more tired you feel. Coffee reduces that feeling of sleepiness when caffeine binds itself to those same receptors, preventing the adenosine from building up.

And it’s not just coffee. Hidden caffeine appears in all manner of other foods including dark chocolate, some teas, certain soft drinks, and energy drinks. So watch your intake of those, as well.

Within half an hour of drinking a mug of the good stuff, the caffeine will be at its peak effect. This is fine for a while - after all, you feel more alert and able to take on whatever life dares to throw at you. All well and good until you’re trying to fall asleep and suddenly… the caffeine is still there, binded to those receptors and preventing your body from switching off and drifting into a restful sleep.

Too much caffeine has been shown to significantly:

  • Reduce total sleep time
  • Increased time to fall asleep

This is because caffeine takes a while to be flushed from the body. The time taken to remove it is known as a ‘half-life’, which you may remember learning about in school science lessons. A half-life is a way to measure how long it takes to reduce the concentration of something by half. In the case of coffee, the half-life is between five and seven hours.

Say you grab a coffee around 4pm. At 10pm there’s still half of that coffee’s caffeine working its magic on your brain and preventing the adenosine from sending you to sleep. It’s the same as if you had just drunk half a cup of coffee and then got straight into bed: your sleep will suffer. But the effects are felt even longer. Fast forward to 4am and there is still a quarter of a cup working around your brain!


So, if you’re a sleep-loving, coffee-fiend like me you’re probably wondering - what’s the best way to get my daily dose of coffee AND get a good night's sleep? Well the answer is short and sweet: you can have both, but in moderation.

Aim to limit your coffee intake to two cups per day, but ideally one should be enough. And importantly: Ditch the coffee after 3pm. If you’re feeling really brave you could try cutting the coffee for a while and monitor your sleep quality. Let us know how you get on!