Caffeine and Sleep It tastes great, provides a lovely kick but isn't good for sleep

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Caffeine is the most popular drug in the world and we use it to fight off sleepiness but it can impact on your sleep at night. It is of course natural and you can find it in coffee beans, tea leaves and cocoa beans. People consume it all over the world on a daily basis in a variety of forms. Let’s look at how much curbing this drug can help you sleep better.

Caffeine can also be produced synthetically. It’s consumed to increase alertness and fight off sleepiness. Caffeine activates part of the brain associated with attention, vigilance and anxiety. There is no nutritional need for caffeine, it tastes great and gives a little kick.

This week is the start of me quitting coffee for a month. Or to be more precise, this week is the first week I start cutting down on caffeine to prepare for quitting coffee for a month. Yes, the cutting down process is going to take a month. I drink between three and five coffees a day, two or three shots per drink. That’s a lot of coffee and cutting down isn’t going to be easy. I want to see how it’s affecting my sleep.

So how does it affect you and your sleep?

Caffeine works remarkably quickly. It’s absorbed into your blood through the stomach and small intestine. Absorption starts after just 15 minutes of consumption, reaches its peak within 30 minutes and by 45 minutes 99% of the caffeine is absorbed. Caffeine goes via the liver to the brain, which gets the full brunt of the caffeine.

Caffeine is a stimulant and most folks know caffeine isn’t great for your sleep, it affects your sleep by preventing a substance in your body called adenosine from working. Adenosine is a neurotransmitter and promotes sleepiness and helps the brain slow down and relax. Caffeine binds to the adenosine receptors in your brain and acts to block the chemical from binding to these receptors. It’s by binding to the receptors that, adenosine would normally induce sleep.

Caffeine can also affect your body clock, your circadian rhythm and suppresses melatonin production. Melatonin is usually produced in the evening in response to decreasing levels of light and is the principal hormone for controlling the synchronisation of sleep. Caffeine does this by disrupting the neurotransmitters that trigger melatonin release. A 2015 controlled study found that a double espresso three hours before bed was enough to delay the circadian rhythm by 40 minutes in test subjects. In effect, the caffeine was extending the body clock’s day length. Caffeine does this by delaying the melatonin rhythm.

Caffeine also affects the quality of sleep, significantly reducing the amount of and quality of all stages of NREM sleep.

Our sensitivity to the effects of caffeine on our sleep is highly variable.  A 2016 review of the research found individuals respond very differently to caffeine depending on age, time of consumption, genetic variability, sensitivity levels and caffeine intake routine.

If, like me, you’re thinking ‘I’ve built up a tolerance so it doesn’t affect my sleep’ I’ve got bad news.  I’m afraid it’s been well documented that any caffeine tolerance you’ve built up doesn’t reduce its affect on your sleeping.  What’s more ‘tolerance’s’ ugly sister is of course dependence.  The result is poorer sleep quality, increase sleep disturbance and daytime dysfunction. Great.

Package all this up and it’s called ‘caffeine-induced sleep disorder’.

Caffeine can make you tired

Yes, the bad news gets worse. Caffeine can make you more tired during the day. Whilst binding to the adenosine receptors levels of adenosine build up behind it. As the caffeine wears off there is a rush of this sleep inducing neurotransmitter. This will make you tired.

Caffeine is diuretic, particularly tea and coffee. As you drink more, you’ll use the loo more. You’ll get more dehydrated, your blood thickens slightly and moves through your system more slowly. This reduces the flow of blood and so lowers the amount of oxygen you can get around your system and hey presto, you feel more tired.

And what do people do in response to feeling more tired? Drink more coffee of course!

Good side of caffeine

It’s not all bad news. Caffeine is an effective stimulant and can be used to improve reaction speeds, concentration, mood, physical and mental performance and help us exercise and burn calories. Some studies suggest it lowers the risk of heart disease, strokes and type 2 diabetes. In fact, doses of 500 milligrams (mg) of caffeine (four huge coffee’s or three energy drinks) can have the same effect of a low dose of amphetamine!

As caffeine delays your circadian rhythm it can be used to get over jet lag. You can in effect put your body clock on hold using caffeine and allow the time of day to catch you up. This approach is highly disruptive but can be effective when used in conjunction with other methods of tackling jet lag.

Doses of 200 – 400 mg of caffeine have been shown to be effective in improving performance across a range of functions and are routinely used to sustain and enhance performance.

But hang on before you head to your nearest café. Like anything you consume your body will build up a tolerance. As such, if you – like me – routinely take caffeine it becomes less effective as a stimulant. The end result is you need your usual caffeine fix to maintain normal performance rather than it boosting normal performance. Not good.

How much caffeine are you consuming?

Coffee and energy drinks now seem to be everywhere. On my way to work every other person seems to have a paper coffee cup or a large black can of energy juice in their hands – what did we all do before these were available? How much are we all drinking – do we even know?

Caffeine consumption is increasing, as are the size of the doses per serving and its general availability. The average person consumes 150 – 500 mg of caffeine. The average tea drinker in England drinks 600 mg of caffeine. We do love our tea. The average caffeine consumption in America is half that at about 300 mg per person per day.

Doses of caffeine vary depending on what you’re consuming, some doses are:

A single 1 oz. shot of coffee, a cup of instant (8 oz.) or an espresso contains about 60 – 70 mg of caffeine
A cup of tea has about 20 – 60 mg of caffeine depending on the make
Energy drinks (usually served as 16 oz.) have 150 – 180 mg.
Medications can range from 100 – 250 mg of caffeine

But a warning, comparing apples with apples is not the case with coffee. In 2003 some crafty scientists from the University of Florida bought a 16 oz cup of the same type if coffee every day for six days and found the caffeine ranged from 260 – 560 mg! If you’re trying to control your caffeine levels you might be shooting in the dark a little ordering your next coffee.

Some extremely high doses are available. Servings of 500 mg can be found in 16 oz serving of brewed coffee and there are similarly high doses in energy drinks.

There is of course caffeine ‘medication’ such as NoDoz or Pro-Plus. There is now caffeine power available (although I don’t think this has made it to the UK yet). This to me seems crazy. There are very serious side effects to consuming too much caffeine.

The last coffee of the day

Caffeine stays in your body for a long time and can disrupt sleep hours after it’s consumed. The time it takes a substance to degrade is measured in half lives. A half-life is the time it takes for any given substance to reduce by half. Coffee has a half-life of 3 to 5 hours depending on your metabolism.

So if I have a flat white at 3:30pm in the afternoon and then a cortado at 4pm (this is how I often finish my Fridays) I will have consumed four or five shots of coffee, 300 – 350 mg of caffeine. By 8 pm and after one half-life I’ve got about 175 mg in my body and by midnight and another half-life down I still have about 80 mg in my system, the equivalent of an espresso. Is having a shot of coffee at midnight a good idea? No. Is my afternoon coffee affecting my sleep on a Friday? Yes, clearly.

So when should I stop drinking coffee? A quick look through the science and recommendations of when to stop drinking caffeine range from 4 – 11 hours before bed time.

A 2013 study published in the Journal of Clinical Sleep Medicine found a fixed dose of caffeine (400 mg) administered at 0, 3, and 6 hours prior to bedtime significantly disrupts sleep. The study concluded that moderate doses of caffeine 3 or 6 hours prior to bedtime can significantly affect sleep and that taken 6 hours before bed reduced total sleep time by 40 – 60 minutes.  Effects become more pronounced in older adults as our ability to break down caffeine reduces. This study finished off by saying if this level – 400 mg of caffeine – intake, and associated disruption to sleep continued, it would have detrimental effects on daytime functioning. Oh, but they taste so good!

Should I stop drinking caffeine?

Short answer is, caffeine can really affect your sleep and we shouldn’t be drinking so much. It can enhance performance but not when used routinely. So think about your use.

Studies have found a discrepancy between subjective and objective measures of sleep disruption following caffeine, in other words we’re really bad at knowing how our sleep has been disrupted by caffeine. So stick to rules based on science rather than your perception.

Some useful ‘rules’ to try and follow are:

  1. Try to limit yourself to 400 mg of caffeine a day, this looks like one of the below:
    • 4 cups of normal (8 oz.) coffee
    • 2 flat whites
    • 2 energy drinks
    • 5 or 6 cups of tea
  2. Try and stop consuming caffeine after 14:00, absolutely don’t drink caffeine after 17:00.
  3. Avoid the mega-strength caffeine drinks such as 16 or 20 oz coffee drinks or large energy drinks.
  4. Stay clear of caffeine powered medications.

Caffeine is not a substitute for sleep. If you’re feeling tired and would usually resort to caffeine; work on your sleep hygiene or develop a sleeping plan to sleep better. You can still use caffeine to increase performance but use it only when you need to and it won’t work anyway if you are dependent on it and have built up a tolerance.

How dependent is dependent?

In 2013 The American Psychiatric Association updated its Diagnostic and Statistical Manual of Mental Disorders. For the first time since 1952 it includes caffeine withdrawal. Caffeine dependency is a thing and it takes remarkably little to become dependent.

The effects of coming off caffeine includes reduced alertness, drowsiness, muscle aches and headaches. These symptoms begin about 12 – 24 hours and peak 24 – 48 hours after cessation. The good news is you can avoid symptoms altogether if caffeine is decreased progressively.

So there we go. Come off it slowly, go for 50 mg reduction, or about a shot of coffee, a day. Oh, and don’t forget all your sources of caffeine, chocolate included!

So my month long reduction beings….

Written by
Sam Billington

Sam is our sleep guru. I am fascinated by sleep and I've used my science training to research and learn about sleep. I have been providing sleep advice and personal sleep plans for years. My day job is Head of Workplace Culture in Defra, I live in London with my wife and have a PhD in Ecology and Biology.