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So far, we've spoken about
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all of the wonderful
benefits that sleep provides,
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but how much sleep should
we actually be getting?
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[Sleeping with Science]
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(Music)
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For the average adult,
the current recommendation
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is somewhere between seven to nine
hours of sleep a night.
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And what we've been finding
from large-scale epidemiological studies
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is that, using that reference point
of seven to nine hours,
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once you start to drop below that,
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your mortality risk
actually starts to increase.
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In fact, the Center for Disease Control
in the United States, or the CDC,
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they stipulate a minimum
of seven hours of sleep a night
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for the average adult.
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In other words, the shorter your sleep,
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the shorter your life.
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But it turns out that it's not quite
a linear relationship as you would expect.
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It's not as though the more
and more that you sleep,
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the lower and lower
your mortality risk is.
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In fact, something strange happens.
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Once you get past nine hours,
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you actually start to see
a rise back up in mortality risk,
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which seems rather strange and peculiar.
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And scientists have actually put forward
at least two different explanations.
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The first is that,
if you look at those studies,
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it may be that individuals are suffering
from significant disease and illness.
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When we become infected,
or we have disease,
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typically, we try to sleep longer,
we stay in bed longer.
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So in other words,
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it was the unmeasured disease
and sickness in those studies
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that was triggering
a response in those individuals
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to try and sleep more.
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That's one explanation.
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The second possible explanation
is poor sleep quality,
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because we know that sleep quality,
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independent of sleep quantity,
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is also associated with mortality risk.
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And the lower that your
quality of sleep is,
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the higher your risk of death.
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People who have poor quality of sleep
will typically try to sleep longer;
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they'll try to stay in bed longer
to overcome that poor quality of sleep.
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It may be poor quality of sleep
masquerading as long sleep
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that is associated
with a higher risk of death,
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rather than the long sleep itself.
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But if we take a step back
and think about society overall,
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I think modernity is constantly pushing us
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to, perhaps, work long hours
and therefore neglect our sleep.
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But if we want to be around
long enough to get the benefits
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and the fruits of all of that hard labor,
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we may want to think about starting
to prioritize our sleep some more.