How much sleep do you need?

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• The CDC recommends getting seven to nine hours of sleep
  per night, but individual needs vary.
• Sleep deprivation is
  associated with serious health issues, including increased
  risk for obesity, diabetes, high blood pressure, and
  stroke.
• Here are five factors that will help you figure out
  what your sleep
  patterns are and how they compare to the larger
  population.

In theory, sleep should take up about eight out of every 24
hours, a third of our lives.

But many of us don’t actually sleep that much and are
tired all the time. More than one third of Americans
don’t
get the seven to nine hours of sleep per
night that the CDC recommends, and according to
research by the National Sleep Foundation, more than a
third of Americans say their sleep quality is “poor” or
“only fair.”

That’s certainly true for Tesla CEO Elon Musk, who recently

told the New York Times that he’s been logging
120-hour work weeks. Musk acknowledged that his
exhaustion is likely taking a toll on his health.

“It’s not been great, actually,” Musk told the Times. “I’ve had
friends come by who are really concerned.”

So how much sleep do we really need?

Like most health factors, there isn’t a one-size- fits-all answer
— sleep needs vary from person to person. There are some incredibly
rare people who can actually get by on a few hours of sleep
per night, and others on the opposite end of the spectrum that
doctors refer to as a “long
sleepers” because they need 11 hours nightly.

But research on sleep can help you figure out how much you need
and how to better get a night’s rest. Here are five facts that
will help you figure out what your personal sleep patterns are
and how they compare to the rest of the population.

There’s a reason that doctors recommend seven to nine hours of
sleep

Notice, the vast majority of people need between seven
and nine hours of sleep.

Internal
Time: Chronotypes, Social Jet Lag, and Why You’re So Tired by
Till Roenneberg

The amount of sleep people need falls into a bell-curve
distribution: the vast majority of the population needs between
seven and nine hours of rest each night to be refreshed.

The chart to the right, from the book “Internal
Time: Chronotypes, Social Jet Lag, and Why You’re So Tired”
by German chronobiologist Till Roenneberg, shows the general
distribution of sleep needs. (Chronobiology is the science of our
internal clocks.)

According to CDC data, getting less than seven hours per night is
“associated with increased risk for obesity, diabetes, high blood
pressure, coronary heart disease, stroke, frequent mental
distress, and all-cause mortality.”

Sleep deprivation can also hurt cognitive performance(as many of
us have probably experienced), and that in turn “can increase the
likelihood of motor vehicle and other transportation accidents,
industrial accidents, medical errors, and loss of work
productivity,” the CDC says.

You have a natural chronotype, or body clock, that determines
when you are most comfortable sleeping and being awake

Most of us think of
ourselves as morning or night people, but those divisions
aren’t scientific — they’re just ways of comparing ourselves to
one another. 

“Where you define owl or lark is really arbitrary,” says Dr. David Welsh, an
associate professor studying circadian clocks at UC San
Diego.

Welsh says that if you look at large surveys of populations, you
get a normal distribution of chronotypes — most people have
fairly “average” chronotypes, some prefer to get up a bit earlier
or later, and small groups naturally rise extremely
early or late. There’s no line that distinguishes different
chronotypes.

But we all have an internal schedule that makes us feel awake or
sleepier at different times of day. Because of factors including
hormone levels, genetics, and light exposure, some of us are more
alert in the mornings and some of us prefer times later in the
day.

If your schedule isn’t aligned with your chronotype, you will
feel tired and out of sync.

The amount of sleep you need changes throughout your life

National Sleep Foundation

The seven-to-nine-hour rule is standard for adults, but kids need
much more sleep, while some older people need less.

This chart by the National Sleep Foundation shows how these
requirements change as kids grow up.

In addition to sleep hour needs changing, chronotypes change
throughout life as well.

According to Roenneberg’s book, young children naturally tend to
be more morning oriented. Around puberty, they’re more likely to
shift into a night owl chronotype, which tends to shift back to
an earlier chronotype after age 20.

There are things you can do to adjust your natural chronotype

While your sleep needs (when you feel alert and how much sleep
your body requires)
are mostly genetic, there are certain things you can do to
adjust your schedule and make
it a bit easier to get up or go to sleep earlier.

Our bodies respond to light, especially the powerful natural
light of the sun. Being exposed to that light in the morning
tells our body that it’s time to be alert and moving. At night,
sitting in the dark stimulates the production of the hormone
melatonin, which helps us relax and fall asleep (we mess with
this process by looking at
bright light from smartphones).

But we can adjust this to a
degree by controlling our exposure to light. This process,
called entrainment, is what our bodies have to do when we go to a
different time zone — this is why we get jet lagged. But we can
also use this to train our bodies to get up and go to sleep
earlier by exposing ourselves to natural light in the morning and
avoiding bright light at night.

This won’t turn you into a morning person, but it can make prying
the covers loose just a little less painful.

Your sleep needs are personal; try to figure out what works for
you

Sometimes new research will come out, and
people will claim something like “studies have found that
seven hours is the optimal amount of sleep — not eight.”

But as interesting as any sleep research is, different people
simply have different needs. The findings of one study don’t
translate into recommendations for everyone. In the case of sleep, experts recommend
figuring out what works best for you.

If you can let yourself sleep naturally for a few days to a week
— going to bed when you are tired and waking up whenever is
natural, preferably while limiting alcohol and caffeine — you’ll
have a better idea of your individual needs. During those days,
try to get some sun and some exercise.

If you do all that and still have trouble sleeping, it might be
time to talk to a doctor. You could be
one of the large percentage of the population with
undiagnosed sleep apnea, especially if you snore. Or you could
have
some other disorder that can be addressed.

It’s worth taking the time to figure out what you can do to sleep
better, since deprivation
raises some serious health concerns.