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