How much sleep do you really need?

You know you need to get enough sleep, but the question remains: How much is enough? Sleep scientist Matt Walker tells us the recommended amount for adults and explains why it's necessary for your long-term health.

So far, we've spoken about

all of the wonderful
benefits that sleep provides,

but how much sleep should
we actually be getting?

[Sleeping with Science]

(Music)

For the average adult,
the current recommendation

is somewhere between seven to nine
hours of sleep a night.

And what we've been finding
from large-scale epidemiological studies

is that, using that reference point
of seven to nine hours,

once you start to drop below that,

your mortality risk
actually starts to increase.

In fact, the Center for Disease Control
in the United States, or the CDC,

they stipulate a minimum
of seven hours of sleep a night

for the average adult.

In other words, the shorter your sleep,

the shorter your life.

But it turns out that it's not quite
a linear relationship as you would expect.

It's not as though the more
and more that you sleep,

the lower and lower
your mortality risk is.

In fact, something strange happens.

Once you get past nine hours,

you actually start to see
a rise back up in mortality risk,

which seems rather strange and peculiar.

And scientists have actually put forward
at least two different explanations.

The first is that,
if you look at those studies,

it may be that individuals are suffering
from significant disease and illness.

When we become infected,
or we have disease,

typically, we try to sleep longer,
we stay in bed longer.

So in other words,

it was the unmeasured disease
and sickness in those studies

that was triggering
a response in those individuals

to try and sleep more.

That's one explanation.

The second possible explanation
is poor sleep quality,

because we know that sleep quality,

independent of sleep quantity,

is also associated with mortality risk.

And the lower that your
quality of sleep is,

the higher your risk of death.

People who have poor quality of sleep
will typically try to sleep longer;

they'll try to stay in bed longer
to overcome that poor quality of sleep.

It may be poor quality of sleep
masquerading as long sleep

that is associated
with a higher risk of death,

rather than the long sleep itself.

But if we take a step back
and think about society overall,

I think modernity is constantly pushing us

to, perhaps, work long hours
and therefore neglect our sleep.

But if we want to be around
long enough to get the benefits

and the fruits of all of that hard labor,

we may want to think about starting
to prioritize our sleep some more.