Sleep Cycles and Stages, Lack of Sleep, and
How to Get the Hours You Need
When you’re
scrambling to meet the countless demands of your day, cutting back on sleep
might seem like the only answer. Who can afford to spend so much time sleeping,
anyway? The truth is you can’t afford not to. Even minimal sleep loss takes a
toll on your mood, energy, and ability to handle stress. By understanding your
nightly sleep needs and what you can do to bounce back from chronic sleep loss,
you can finally get on a healthy sleep schedule.
The power of sleep
Many of us try to sleep as little as possible. There are
so many things that seem more interesting or important than getting a few more
hours of sleep, but just as exercise and nutrition are essential for optimal
health and happiness, so is sleep. The quality of your sleep directly affects the
quality of your waking life, including your mental sharpness, productivity,
emotional balance, creativity, physical vitality, and even your weight. No
other activity delivers so many benefits with so little effort!
Understanding sleep
Sleep isn’t exactly a time when your body and brain shut
off. While you rest, your brain stays busy, overseeing a wide variety of
biological maintenance that keeps your body running in top condition, preparing
you for the day ahead. Without enough hours of restorative sleep, you won’t be
able to work, learn, create, and communicate at a level even close to your true
potential. Regularly skimp on “service” and you’re headed for a major mental
and physical breakdown.
The good news is that you don't have to choose between
health and productivity. As you start getting the sleep you need, your energy
and efficiency will go up. In fact, you're likely to find that you actually get
more done during the day than when you were skimping on shuteye.
Myths and Facts about Sleep
Myth 1: Getting just one hour less sleep per night won’t affect
your daytime functioning.You may
not be noticeably sleepy during the day, but losing even one hour of sleep can
affect your ability to think properly and respond quickly. It also compromises
your cardiovascular health, energy balance, and ability to fight infections.
Myth 2: Your body adjusts quickly to different sleep schedules. Most people can reset their biological clock, but only by
appropriately timed cues—and even then, by one or two hours per day at best.
Consequently, it can take more than a week to adjust after traveling across
several time zones or switching to the night shift.
Myth 3: Extra sleep at night can cure you of problems with
excessive daytime fatigue. The
quantity of sleep you get is important, sure, but it's the quality of your sleep that you really have to
pay attention to. Some people sleep eight or nine hours a night but don’t feel
well rested when they wake up because the quality of their sleep is poor.
Myth 4: You can make up for lost sleep during the week by sleeping
more on the weekends. Although
this sleeping pattern will help relieve part of a sleep debt, it will not
completely make up for the lack of sleep. Furthermore, sleeping later on the
weekends can affect your sleep-wake cycle so that it is much harder to go to
sleep at the right time on Sunday nights and get up early on Monday mornings.
Adapted from: Your Guide to Healthy Sleep (PDF) The National Institutes of
Health
According to the National Institutes of Health, the
average adult sleeps less than seven hours per night. In today’s fast-paced
society, six or seven hours of sleep may sound pretty good. In reality, though,
it’s a recipe for chronic sleep deprivation.
There is a big difference between the amount of sleep you
can get by on and the amount you need to function optimally. Just because
you're able to operate on seven hours of sleep doesn't mean you wouldn't feel a
lot better and get more done if you spent an extra hour or two in bed.
While sleep requirements vary slightly from person to
person, most healthy adults need between seven and a half to nine hours of
sleep per night to function at their best. Children and
teens need even more (see Average Sleep Needs table below). And despite the
notion that our sleep needs decrease with age, older people still need at least
seven and a half to eight hours of sleep. Since older adults
often have trouble sleeping this
long at night, daytime naps can help fill in the gap.
The best way to figure out if you're meeting your sleep
needs is to evaluate how you feel as you go about your day. If you're logging
enough hours, you'll feel energetic and alert all day long, from the moment you
wake up until your regular bedtime.
Sleep needs and peak performance
There is a big difference between the amount of sleep you
can get by on and the amount you need to function optimally. Just because
you’re able to operate on seven hours of sleep doesn’t mean you wouldn’t feel a
lot better and get more done if you spent an extra hour or two in bed. The best
way to figure out if you’re meeting your sleep needs is to evaluate how you
feel as you go about your day. If you’re logging enough hours, you’ll feel
energetic and alert all day long, from the moment you wake up until your
regular bedtime.
Think six hours of sleep is enough?
Think again. Researchers at the University of California,
San Francisco, discovered that some people have a gene that enables them to do
well on six hours of sleep a night. This gene, however, is very rare, appearing
in less than 3% of the population. For the other 97% of us, six hours doesn’t
come close to cutting it.
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Average Sleep Needs by Age
|
|
|
Newborn
to 2 months old
|
12
- 18 hrs
|
|
3
months to 1 year old
|
14
- 15 hrs
|
|
1
to 3 years old
|
12
- 14 hrs
|
|
3
to 5 years old
|
11
- 13 hrs
|
|
5
to 12 years old
|
10
- 11 hrs
|
|
12
to 18 years old
|
8.5
- 10 hrs
|
|
Adults
(18+)
|
7.5
- 9 hrs
|
If you’re getting less than eight hours of sleep each
night, chances are you’re sleep deprived. What’s more, you probably have no
idea just how much lack of sleep is affecting you.
How is it possible to be sleep deprived without knowing
it? Most of the signs of sleep deprivation are much more subtle than falling
face first into your dinner plate. Furthermore, if you’ve made a habit of
skimping on sleep, you may not even remember what it feels like to be
wide-awake, fully alert, and firing on all cylinders. Maybe it feels normal to
get sleepy when you’re in a boring meeting, struggling through the afternoon
slump, or dozing off after dinner, but the truth is that it’s only “normal” if
you’re sleep deprived.
You may be sleep deprived if you...
- Need
an alarm clock in order to wake up on time
- Rely
on the snooze button
- Have
a hard time getting out of bed in the morning
- Feel
sluggish in the afternoon
- Get
sleepy in meetings, lectures, or warm rooms
- Get
drowsy after heavy meals or when driving
- Need
to nap to get through the day
- Fall
asleep while watching TV or relaxing in the evening
- Feel
the need to sleep in on weekends
- Fall
asleep within five minutes of going to bed
The effects of sleep deprivation and chronic lack of sleep
While it may seem like losing sleep isn't such a big
deal, sleep deprivation has a wide range of negative effects that go way beyond
daytime drowsiness. Lack of sleep affects your judgment, coordination, and
reaction times. In fact, sleep deprivation can affect you just as much as being
drunk.
The effects include:
- Fatigue,
lethargy, and lack of motivation
- Moodiness
and irritability
- Reduced
creativity and problem-solving skills
- Inability
to cope with stress
- Reduced
immunity; frequent colds and infections
- Concentration
and memory problems
- Weight
gain
- Impaired
motor skills and increased risk of accidents
- Difficulty
making decisions
- Increased
risk of diabetes, heart disease, and other health problems
How sleep deprivation can add to your waistline
Ever noticed how when you’re short on sleep you crave
sugary foods that give you a quick energy boost? There’s a good reason for
that. Sleep deprivation has a direct link to overeating and weight gain.
There are two hormones in your body that regulate normal
feelings of hunger and fullness. Ghrelin stimulates appetite, while leptin
sends signals to the brain when you are full. However, when don’t get the sleep
you need, your ghrelin levels go up, stimulating your appetite so you want more
food than normal, and your leptin levels go down, meaning you don’t feel
satisfied and want to keep eating. So, the more sleep you lose, the more food
your body will crave.
All sleep is not created equal. Sleep unfolds in a series
of recurring sleep stages that are very different from one another in terms of
what’s happening beneath the surface. From deep sleep to dreaming sleep, they
are all vital for your body and mind. Each stage of sleep plays a different
part in preparing you for the day ahead.
There are two main types of sleep:
- Non-REM (NREM) sleep consists of three stages of
sleep, each deeper than the last.
- REM (Rapid Eye Movement)
sleep is when you
do most active dreaming. Your eyes actually move back and forth during
this stage, which is why it is called Rapid Eye Movement sleep.
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The Stages of Sleep
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Non-REM
sleep
|
|
Stage N1 (Transition to sleep) – This stage lasts about five minutes. Your eyes move
slowly under the eyelids, muscle activity slows down, and you are easily
awakened.
|
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Stage N2 (Light sleep) – This is the first stage of true sleep, lasting from
10 to 25 minutes. Your eye movement stops, heart rate slows, and body
temperature decreases.
|
|
Stage N3 (Deep sleep) – You’re difficult to awaken, and if you are awakened,
you do not adjust immediately and often feel groggy and disoriented for
several minutes. In this deepest stage of sleep, your brain waves are
extremely slow. Blood flow is directed away from your brain and towards your
muscles, restoring physical energy.
|
|
REM
sleep
|
|
REM sleep (Dream sleep) – About 70 to 90 minutes after falling asleep, you
enter REM sleep, where dreaming occurs. Your eyes move rapidly, your
breathing shallows, and your heart rate and blood pressure increase. Also
during this stage, your arm and leg muscles are paralyzed.
|
Quality sleep and your internal clock
Your internal 24-hour sleep-wake cycle, otherwise known
as your biological clock or circadian rhythm, is regulated by processes in the
brain that respond to how long you’ve been awake and the changes between light
and dark. At night, your body responds to the loss of daylight by producing
melatonin, a hormone that makes you sleepy. During the day, sunlight triggers
the brain to inhibit melatonin production so you feel awake and alert.
Your internal clock can be disrupted by factors such as
nightshift work, traveling across time zones, or irregular sleeping
patterns—leaving you feeling groggy, disoriented, and sleepy at inconvenient
times. The production of melatonin can also be thrown off when you're deprived
of sunlight during the day or exposed to too much artificial light at
night—especially the light from electronic devices, including TVs, computers,
tables, and mobile phones.
The architecture of sleep
You may think that once you go to bed, you soon fall into
a deep sleep that lasts for most of the night, progressing back into light
sleep in the morning when it’s time to wake up. In reality, the sleep cycle is
a lot more complicated.
During
the night, your sleep follows a predictable pattern, moving back and forth
between deep restorative sleep (deep sleep) and more alert stages and dreaming
(REM sleep). Together, the stages of REM and non-REM sleep form a complete
sleep cycle. Each cycle typically lasts about 90 minutes and repeats four to
six times over the course of a night.
The amount of time you spend in each stage of sleep
changes as the night progresses. For example, most deep sleep occurs in the
first half of the night. Later in the night, your REM sleep stages become
longer, alternating with light Stage N2 sleep. This is why if you are sensitive
to waking up in the middle of the night, it is probably in the early morning
hours, not immediately after going to bed.
N.B: When you chart the sleep stages over the course of the night, the result looks like a city skyline—which is why it is called "sleep architecture"
Having a hard time getting up when your alarm goes off?
Even if you’ve enjoyed a full night’s sleep, getting out
of bed can be difficult if your alarm goes off when you’re in the middle of
deep sleep (Stage N3). If you want to make mornings less painful—or if you know
you only have a limited time for sleep—try setting a wake-up time that’s a
multiple of 90 minutes, the length of the average sleep cycle. For example, if
you go to bed at 10 p.m., set your alarm for 5:30 (a total of 7 ½ hours of
sleep) instead of 6:00 or 6:30. You may feel more refreshed at 5:30 than with
another 30 to 60 minutes of sleep because you’re getting up at the end of a
sleep cycle when your body and brain are already close to wakefulness.
It's not just the number of hours in bed that's
important—it's the quality of those hours of sleep. If you're giving yourself
plenty of time for sleep, but you're still having trouble waking up in the
morning or staying alert all day, you may not be spending enough time in the
different stages of sleep.
Each stage of sleep in the sleep cycle offers benefits to
the sleeper. However, deep sleep (Stage N3) and REM sleep are particularly
important. A normal adult spends approximately 50% of total sleep time in Stage
2 sleep, 20% in REM sleep, and 30% in the remaining stages, including deep
sleep.
Deep sleep
The most damaging effects of sleep deprivation are from
inadequate deep sleep. Deep sleep is a time when the body repairs itself and
builds up energy for the day ahead. It plays a major role in maintaining your
health, stimulating growth and development, repairing muscles and tissues, and
boosting your immune system. In order to wake up energized and refreshed,
getting quality deep sleep is essential. Factors that can lead to poor or
inadequate deep sleep include:
- Being woken during the
night by outside
noise, for example, or in order to care for a crying baby.
- Working night shifts or
swing shifts. Getting
quality deep sleep during the day can be difficult, due to light and
excess noise.
- Smoking or drinking in the
evening. Substances
like alcohol and nicotine can disrupt deep sleep. It’s best to limit them
before bed.
REM sleep
Just as deep sleep renews the body, REM sleep renews the
mind by playing a key role in learning and memory. During REM sleep, your brain
consolidates and processes the information you’ve learned during the day, forms
neural connections that strengthen memory, and replenishes its supply of
neurotransmitters, including feel-good chemicals like serotonin and dopamine
that boost your mood during the day.
To get more mind and mood-boosting REM sleep, try
sleeping an extra 30 minutes to an hour in the morning, when REM sleep stages
are longer. Improving your overall sleep will also increase your REM sleep. If
you aren’t getting enough deep sleep, your body will try to make that up first,
at the expense of REM sleep.
Sleep debt is the difference between the amount of sleep
you need and the hours you actually get. Every time you sacrifice on sleep, you
add to the debt. Eventually, the debt will have to be repaid; it won’t go away
on its own. If you lose an hour of sleep, you must make up that extra hour
somewhere down the line in order to bring your “account” back into balance.
Sleeping in on the weekends isn’t enough!
Many of us try to repay our sleep debt by sleeping in on
the weekends, but as it turns out, bouncing back from chronic lack of sleep
isn’t that easy. One or two solid nights of sleep aren’t enough to pay off a
long-term debt. While extra sleep can give you a temporary boost (for example,
you may feel great on Monday morning after a relaxing weekend), your
performance and energy will drop back down as the day wears on.
Tips for getting and staying out of sleep debt
While you can’t pay off sleep debt in a night or even a
weekend, with a little effort and planning, you can get back on track.
- Aim for at least seven and
a half hours of sleep every night. Make sure you don’t fall
farther in debt by blocking off enough time for sleep each night.
Consistency is the key.
- Settle short-term sleep
debt with an extra hour or two per night. If you lost 10 hours of
sleep, pay the debt back in nightly one or two-hour installments.
- Keep a sleep diary. Record when
you go to bed, when you get up, your total hours of sleep, and how you
feel during the day. As you keep track of your sleep, you’ll discover your
natural patterns and get to know your sleep needs.
- Take a sleep vacation to
pay off a long-term sleep debt. Pick a two-week period when
you have a flexible schedule. Go to bed at the same time every night and
allow yourself to sleep until you wake up naturally. No alarm clocks! If
you continue to keep the same bedtime and wake up naturally, you’ll
eventually dig your way out of debt and arrive at the sleep schedule
that’s ideal for you.
- Make sleep a priority. Just as you schedule time
for work and other commitments, you should schedule enough time for sleep.
Instead of cutting back on sleep in order to tackle the rest of your daily
tasks, put sleep at the top of your to-do list.
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