Does caffeine disrupt sleep?

Yesterday the trial began for a Kentucky man, Woody Smith, accused of strangling his wife with an extension cord in May last year. It was reported yesterday that Mr Smith’s lawyer planned to argue* that he killed his wife as a result of insanity brought on by lack of sleep and excessive caffeine consumption. According to reports, Mr Smith was worried his wife would leave him and was taking large amounts of caffeine pills and caffeinated drinks to keep himself awake…..

Sorry for the gloomy opening, but it is rather an intriguing story, and one that highlights the often talked about relationship between caffeine consumption and sleep.

Well, this is one experiment I don’t need to carry out. I already know the results.

Save for herbal and fruit teas every now and then, I’m not a tea-drinker. For the most part, I’m not a coffee-drinker either, although every so often a skinny vanilla latte is an enjoyable treat. I’m not so virtuous, though. I am verging on being a Diet Coke addict.

I do have to be very careful with my Diet Coke habit though. If I drink more than one can of Diet Coke a day, I turn into a quivering wreck. I especially need to be careful with my timing. One can of Diet Coke in the early afternoon is no problem, but if I dare to drink one in the evening, I know I’m going to be punished when I try to go to sleep.

Caffeine – found in tea, coffee, soft drinks, chocolate and some medications – is a central nervous system stimulant used to promote wakefulness. Every day it is consumed by millions of people to help them wake up and ward off drowsiness in the morning and stay alert during the day.

Unsurprisingly (to me) studies have demonstrated that caffeine consumption can have a disruptive effect on sleep – by making it harder to nod off, reducing the amount of deep sleep you enjoy and reducing sleep duration overall. It is well known that the effects of caffeine can persist for several hours and the general rule of thumb is to avoid consuming caffeine at least 6 hours before bed.

Having said all this, my other half can spend the day drinking cup after cup of tea, and down a double espresso after dinner, without suffering any (obvious) consequences. So, why is this? Well, he reckons his long-term, regular caffeine consumption (he’s been a devoted tea-drinker since his early teens) have resulted in him developing a tolerance to the caffeine buzz.

There may be some truth to this. A study by Suzette M. Evans and Roland R. Griffiths in 1991, “Caffeine tolerance and choice in humans” provides evidence of complete tolerance development to a central nervous system effect of caffeine in humans. According to the John Hopkins Bayview Medical Center website

Caffeine-induced sleep disturbance is greatest among individuals who are not regular caffeine users. Although there is evidence for some tolerance to the sleep disrupting effects of caffeine, complete tolerance may not occur and thus habitual caffeine consumers are still vulnerable to caffeine-induced sleep problems.”

An alternative explanation to differences in the effect of caffeine may be that regular caffeine users are less likely to be aware of its effect and any sleep troubles caused by the caffeine than less frequent caffeine consumers.

It seems to me that the sensible approach to caffeine consumption is this:

If you have a problem with sleep, cut out all caffeine – you may not realise that your caffeine consumption is to blame.

If, like me, you know you are sensitive to the effects of caffeine, limit (or, if you can manage it, cut out) your caffeine intake and be particularly vigilant about the timing of any caffeine consumption.

If, like my other half, caffeine has little or no obvious effect on you and you have no problems sleeping – well, lucky you! – but just be mindful that you may still be vulnerable to sleep disturbances caused by your caffeine consumption. And, if you’re up for a challenge, why not see if you can give up your daily caffeine habit – you might find that it’s masking sleep troubles that you had no clue about.

‘Til next time, sleep well x

Click here to read about why the Sleep Geek swapped his builders’ tea for green tea.

* Reports today say that the lawyer for Mr Smith changed his previously laid out strategy and instead argued that Mr Smith’s excessive caffeine consumption left him so sleep-deprived and mentally unstable that he falsely confessed to killing his wife.


  1. I write this a 4 in the morning with a warm drink in hand as I cannot sleep. I’m not sure why but there is something about a hot caffeinated drink late at night that I really crave. It must have quite a big effect on the quality of my sleep yet I still drink tea and coffee out of habit.

    I completely agree with what you say about diet coke as well. It seems to send me running up the ceiling all day, much worse than typical caffeinated warm drinks.

    My girlfriend is such a sound sleeper (and snorer) it drives me (a borderline insomniac sometimes) crazy. I try to drug her with super spiked strong coffee sometimes to keep her awake and it makes absolutely no difference. When she decides it’s time to go to sleep, that’s it, she’s off with the fairies.

    I do binge on caffeine sometimes, I’m going to have to make a real concerted effort to ensure that I don’t drink anything caffeinated 6 hours before going to sleep and see if it makes a big difference.

    Nice post and nice website!!!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: