Sleep
Cycles & 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. Learn how to determine your nightly sleep needs
and what you can do to bounce back from chronic sleep loss and get on a healthy
sleep schedule.
You
can improve your sleep!
Many of us try to sleep as little as
possible—or feel like we have should. 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–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
How many hours of sleep do you need?
|
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
|
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 box at right). 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.
Signs and symptoms of sleep deprivation and lack of sleep
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
Stages of sleep: REM sleep and non-REM sleep stages
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 four 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.
|
The Stages of Sleep
|
|
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.
|
|
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.
|
Understanding the Sleep Cycle
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 2 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.
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.
The importance of deep sleep and REM sleep
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 (Stages 3 and 4) 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.
Paying off your sleep debt
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.
