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Many of us like to start the day with a cup of coffee
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and perhaps end the day with a glass of wine
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or some other kind of alcoholic drink.
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But it turns out that these two substances,
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alcohol and caffeine, can have surprising impacts on our sleep.
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[Sleeping with Science]
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(Music)
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Let's start with caffeine.
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Caffeine is in a class of drugs
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that we call the psychoactive stimulants.
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And everyone knows that caffeine can make them more alert.
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It can wake them up.
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But there are at least two additional,
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hidden features of caffeine
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that some people may not be aware of.
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The first is the duration of action of caffeine.
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Caffeine, for the average adult,
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will have what we call a half-life
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of about five to six hours.
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What that means is that after about five to six hours
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50 percent of that caffeine that you had
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is still circulating in your system.
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What that also means is that caffeine has a quarter-life
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of about 10 to 12 hours.
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In other words, let's say that you have a cup of coffee
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at 2pm in the evening.
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It could be that almost a quarter of that caffeine
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is still swilling around in your brain at midnight.
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And as a result, it can make it harder for an individual
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to fall asleep or even stay asleep soundly
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throughout the night.
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So that's the first feature of caffeine.
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The second issue with caffeine
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is that it can change the quality of your sleep.
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Now some people will tell me
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that I'm one of those individuals
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who can have an espresso with dinner,
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and I fall asleep fine, and I can stay asleep.
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But even if that's true, it turns out
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that caffeine can actually decrease the amount
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of deep, non-rapid eye movement sleep that we have,
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stages three and four of non-REM sleep.
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That's that sort of restorative deep sleep.
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And as a consequence, you can wake up the next morning,
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and you don't feel refreshed,
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you don't feel restored by your sleep.
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But you don't remember waking up,
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you don't remember struggling to fall asleep,
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so you don't make the connection,
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but nevertheless you may then find yourself
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reaching for two cups of coffee in the morning to wake up
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rather than one.
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So that's caffeine, but now let's move on to alcohol,
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because alcohol is perhaps one
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of the most misunderstood sleep aids out there.
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In fact, it's anything but a sleep aid.
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And it can be problematic for your sleep
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in at least three different ways.
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First, alcohol is in a class of drugs
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that we call the sedatives.
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But sedation is not sleep.
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And studies teach us that those two things
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are really quite different.
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Sedation is a case
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where we're simply switching off the firing
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of the brain cells, particularly in the cortex.
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And that's not natural sleep.
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In fact, during deep non-rapid eye movement sleep,
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for example, the brain has this remarkable coordination
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of hundreds of thousands of cells
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that all of a sudden fire together,
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and then they all go silent,
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and then they all fire together, and then they go silent,
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producing these big, powerful brainwaves
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of deep non-REM sleep.
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And so that's the first way
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in which alcohol can be problematic.
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We're mistaking sedation for deep sleep.
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The second problem with alcohol
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is that it can actually fragment your sleep.
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Alcohol can actually trigger and activate during sleep
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what we call the fight or flight branch
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of the nervous system,
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which will therefore wake you up more frequently
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throughout the night.
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And alcohol can even increase the amount
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of alerting chemicals that are released by the brain,
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once again fragmenting your sleep.
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The third and final issue with alcohol and sleep
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is that alcohol can actually block
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your rapid eye movement sleep, or your dream sleep.
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And as we'll learn in subsequent episodes,
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REM sleep, or rapid eye movement sleep, dream sleep,
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provides a collection of benefits,
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things such as your emotional
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and mental health, even creativity.
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Now I'm not here to tell anyone how to live.
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I don't want to be puritanical.
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I'm just a scientist.
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What I want to try and do is provide you
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with the information about the relationship
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between caffeine and alcohol on your sleep
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so then you can make an informed choice
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as to how best you want to live your life
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when you're trying to prioritize your sleep health.
