What is the body clock?
body's "biological clock," or 24-hour cycle (circadian rhythm), can be affected by light or darkness, which can make the body
think it is time to sleep or wake up. The 24-hour body clock controls functions
- Sleeping and waking.
- The balance of body fluids.
- Other body
functions, such as when you feel hungry.
How are body clock problems and sleep problems connected?
Body clock sleep problems have been
linked to a hormone called
melatonin, which helps your body fall and stay asleep. Light and dark affect how the body makes
melatonin. Most melatonin is made at night. During the day, light tells your
body to make less melatonin. If you work at night in artificial light, your
body may be making less melatonin than it needs.
as those who can't sleep until very late and those who go to bed very
early—have circadian (say "ser-KAY-dee-un") rhythms that are different from those of most people. Other people with sleep problems may have regular
circadian rhythms but have to adjust them to new situations, such as working a
What sleep problems are related to problems with your body clock?
Things that may affect
melatonin production and can cause sleep problems include:
- Jet lag. Crossing time
zones disrupts your body clock. You have sleep problems because your body clock
has not adjusted to the new time zone. Your body thinks that you're still in
your old time zone. For example, if you fly from Chicago to Rome, you cross
seven time zones. This means that Rome is 7 hours ahead of Chicago. When you
land in Rome at 6:00 in the morning, your body thinks it's still in Chicago at
11:00 the previous night. Your body wants to sleep, but in Rome the day is just
- Changing your sleep schedule. When
you work at night and sleep during the day, your body's internal clock needs to
reset to let you sleep during the day. Sometimes that's hard to do. People who
work the night shift or rotate shifts may have trouble sleeping during the day
and may feel tired at night when they need to be alert for
- Your sleep environment. Too much light
or noise can make your body feel like it is not time to sleep.
- Illness. Certain illnesses and health
problems can affect sleep patterns. These include dementia, a head injury,
recovering from a coma, and severe depression. Some medicines that affect the
central nervous system may also affect sleep patterns.
- Aftereffects of drugs and alcohol. Some drugs cause sleep problems. And you may fall
asleep with no problems after drinking alcohol late in the evening, but
drinking alcohol before bed can wake you up later in the night.
Other sleep problems related to the body clock
- Having a hard time falling asleep until very
late at night or very early in the morning and then feeling tired and needing
to sleep during the day. People who have this problem may be called "night
owls." This is a common problem, and it usually starts in the early teen or
young adult years. People who have a parent with this problem are more likely
to have it themselves.
- Falling asleep early—at 8 p.m. or
earlier—and waking up early—between 3 a.m. and 5 a.m. If you wake up early, you
may be called an "early bird." This problem is not as common as staying up late
and waking up late. Experts are not sure what causes it.
How can you treat sleep problems related to your body clock?
How you treat a sleep problem related to
your body clock depends on what is causing the problem. Here are some tips for
the most common problems.
Taking melatonin supplements may help reset your body clock. Studies
show that melatonin has reduced the symptoms of jet lag for people flying both
east and west.1
Suggestions about times
and dosages vary among researchers who have studied melatonin. Doctors
recommend that you:
- Take melatonin after dark on the day you travel
and after dark for a few days after you arrive at your destination.
- Take melatonin in the evening for a few days
before you fly if you will be flying east.
The safety and effectiveness of melatonin have not been
thoroughly tested. Taking large doses of it may disrupt your sleep and make you
very tired during the day. If you have epilepsy or are taking blood thinners
such as warfarin (Coumadin), talk to your doctor before you use melatonin.
The sleeping pills eszopiclone (Lunesta) and zolpidem (Ambien) have been studied for jet lag. They may help you sleep despite jet lag if you
take them before bedtime after you arrive at your destination. Side effects include headaches, dizziness, confusion, and
feeling sick to your stomach.
For more information on jet lag, see:
- Sleep Problems: Dealing With Jet Lag.
If you work
the night shift or rotate shifts, you can help yourself get good sleep by
keeping your bedroom dark and quiet and by taking good care of yourself
overall. In some cases, prescription medicine or over-the-counter supplements
may help. Here are some tips on sleeping well when you do this type of shift
- Make sure that the room where you sleep is
dark. Use blackout drapes, or wear a sleep eye mask.
- Wear earplugs
to block sounds.
- Don't have alcohol or caffeine in the hours
leading up to bedtime.
- Take a nap during a work break if you can.
- Ask your doctor if you should try a dietary supplement or
medicine. Doctors usually advise people to use a supplement or medicine only
for a short time.
For more information, see the topic
Shift Work Sleep Disorder.
Some people, no matter what
they do, have trouble falling asleep at night and being up early during the
day. This may or may not cause problems for them. It depends on their lifestyle
and work or school schedule. If you are one of those night owls, there are
things you can try so that you fall asleep earlier and sleep through the
- Getting up at the same time every day no matter what time you go to sleep. On the weekends (or on
days when you don't have to get up), don't let yourself sleep more than 1 hour
longer than you do when you have to get up for work or school. If that doesn't
work, you can try the treatments listed below.
- Light therapy. In this case, light therapy means exposing
yourself to bright light as soon as you wake up. You can use sunlight or a
bright (10,000 lux) light box for 30 to 45 minutes each day.
- Melatonin. Ask your doctor
about taking melatonin supplements in the evening to help you get to
- Chronotherapy. For night owls, this
method involves creating a 27-hour day. During each sleep-wake cycle, you go to
sleep 3 hours later until the time to go to sleep has cycled back around to the
time you actually want to go to sleep. After you complete the cycle once, then
you would keep going to bed at that desired time. This method can be hard to do
because of the way it can disrupt your daily schedule and because you have to
keep to a rigid schedule. Here is a sample schedule:
- Day 1: If you normally go to bed at
midnight, you would wait until 3 a.m. to go to sleep.
- Day 2 and
beyond: Go to sleep at 6 a.m., and then keep delaying sleep 3 hours each day
until you are going to bed at the time you desire. This will probably take 5 to
fall asleep very early and wake up before dawn may try the following to try to
stay up later at night and sleep later in the morning.
- Light therapy. In this
case, light therapy means exposing yourself to bright light in the evening. Use
a bright (10,000 lux) light box for 30 to 45 minutes each
- Antidepressant medicine. A doctor may
prescribe antidepressants along with having you try to stay up 15 minutes later
every few days. This treatment is usually for people who are depressed in
addition to having sleep problems.
- Chronotherapy. For early birds, this method involves creating
a 21-hour day. During each sleep-wake cycle, you go to bed 3 hours earlier
until the time to go to sleep has cycled back around to the time you actually
want to go to sleep. This method can be hard to do because of the way it can
disrupt your daily schedule and because you have to keep to a rigid schedule.
Here is a sample schedule:
- Day 1: If you normally go to bed at 8 p.m.,
you would go to bed at 5 p.m.
- Day 2 and beyond: Go to bed at 2
p.m., and then keep going to sleep 3 hours earlier each day until you are going
to bed at the time you desire. This will probably take about a week. Then you
would keep going to bed at that desired time.
After you get
treatment for the illness or health problem that is causing your sleep problem,
you will need to practice good sleep habits. This includes getting regular
exercise (but not within 3 or 4 hours of your bedtime), going to bed at the
same time each day, and using the bed only for sleep and sex.
For more tips on improving sleep habits, see:
- Insomnia: Improving Your Sleep.
Health Tools help you make wise health decisions or take action to improve your health.
Actionsets are designed to help people take an active role in managing a health condition.
- Insomnia: Improving Your Sleep
- Sleep Problems: Dealing With Jet Lag
- Insomnia: Improving Your Sleep
- Sleeping Better
Herxheimer A (2008). Jet lag, search date June 2008. Online version of BMJ Clinical Evidence: http://www.clinicalevidence.com.
Other Works Consulted