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Sleep apnea is a condition in which breathing stops during sleep. If you have sleep apnea, your breathing will stop and then start again repeatedly throughout the night.

There are three forms of sleep apnea:  obstructive sleep apnea, central sleep apnea and complex sleep apnea.

People with sleep apnea are said to suffer from a form of Sleep Disordered Breathing (SBD).

Sleep hypopnea is a type of SBD that occurs when breathing becomes severely restricted at times during sleep, but it does not stop completely.  Often, people with sleep hypopnea are said to have sleep apnea.

Obstructive Sleep Apnea

More than 95% of people with sleep apnea suffer from obstructive sleep apnea, or OSA.

Obstructive sleep apnea is caused by the throat muscles becoming too relaxed, which causes the airway to become too narrow for air to get through.

If you suffer from obstructive sleep apnea, you will stop breathing when your airway becomes blocked. As soon as your brain senses that you aren't getting enough oxygen, it will wake you up so you start breathing again.

This happens so quickly that you don't even realize that you have been awake.

However, these awakenings can occur hundreds of times a night - as often as every 30 seconds if your sleep apnea is very severe.  All of those brief awakenings add up, so that during the day you feel like you have had hardly any sleep at all.

Obstructive sleep apnea is most likely to occur during REM sleep, when your muscle tone becomes more relaxed. During REM sleep, the muscles in your throat relax, and it is normal for your airways to become partially blocked. This can cause sufferers of sleep paralysis to imagine that they are suffocating, or to hallucinate that someone or something is trying to choke them or to suffocate them.

With sleep apnea, the airway becomes so blocked during REM sleep that there is a dangerous drop in oxygen levels.

Snoring and Obstructive Sleep Apnea

People with obstructive sleep apnea often snore very loudly because air is trying to get through a very constricted airway.

The type of snoring that is exhibited by people with obstructive sleep apnea does not sound like normal snoring.

Normal snoring has a rhythmic quality, as it follows natural, healthy breathing rhythms.

In sleep apnea, there is a pattern of loud snoring followed by a moment of silence when breathing stops entirely. This is then followed by a loud snorting noise, which occurs when the sufferer awakens briefly and the airway opens.

Normally, snoring is least likely to occur during REM sleep, because breathing is shallowest during REM sleep.  People who do not suffer from sleep apnea are most likely to snore during NREM sleep, particularly during Stage 3 and Stage 3 sleep (deep sleep).

People with obstructive sleep apnea are most likely to snore during REM sleep, because that is when the throat muscles are most relaxed and when the airways are most likely to be blocked.

Risks of Developing Obstructive Sleep Apnea

Obstructive sleep apnea runs in families.

Men are more likely to have obstructive sleep apnea than women, and people over the age of 65 are more likely to have obstructive sleep apnea than younger people

Children may develop obstructive sleep apnea if their tonsils or their adenoids are enlarged.

Being overweight or having a thick neck can increase your risk of obstructive sleep apnea.  This is because excess fat around your airway may make your airway too narrow for air to pass through when you are sleeping.

Smoking increases your chances of developing obstructive sleep apnea, as does drinking alcohol before bed, because alcohol relaxes the muscles in your throat.

Treating Obstructive Sleep Apnea

If you have obstructive sleep apnea and you are overweight, it is important that you try to lose weight.  If you smoke, you should try to quit smoking.

Avoid sleeping on your back if you have obstructive sleep apnea, because that can restrict your airway even more.

Some people with obstructive sleep apnea wear a mouthpiece that pushes the jaw forward or holds the tongue out of the way, in order to make the airway wider.

If your obstructive sleep apnea is severe, you may have to sleep with a Continuous Positive Airway Pressure (CPAP) machine.  A CPAP machine provides continuous air pressure through a mask that you wear over your nose. This helps to keep your airway open.

People with obstructive sleep apnea sometimes have surgery to remove enlarged adenoids or tonsils or surgery to remove extra tissue in their noses and throats.

Central Sleep Apnea

Central sleep apnea is an uncommon form of sleep apnea.

It is caused by a problem with the brain.

If you have central sleep apnea, when you are asleep, your brain doesn't send the right signals to your breathing muscles to make sure you keep breathing.

As with obstructive sleep apnea, central sleep apnea is likely to cause frequent awakenings at night and extreme sleepiness during the day.

People with central sleep apnea are more likely to remember waking up in the middle of the night than people with obstructive sleep apnea.  If you have central sleep apnea, you may wake up suddenly, in the middle of the night, and feel out of breath.

Risks of Developing Central Sleep Apnea

Having heart disease or having had a stroke increases your risk of developing central sleep apnea.

Men are more likely to have central sleep apnea than women.  People over 65 are more likely to have central sleep apnea than people who are younger.

Using opiates, such as morphine or codeine can cause central sleep apnea.

If you sleep at a higher altitude than you are used to, where the level of oxygen in the air is thinner, you may suffer from central sleep apnea temporarily. Your sleep apnea will stop as soon as you return to a lower altitude.

Treating Central Sleep Apnea

A doctor may try to treat central sleep apnea by treating the condition that is causing it, for example, by providing therapy for a heart condition.

If you have central sleep apnea and are taking opiates, the doctor may wean you off them.

A CPAP machine can sometimes be used to treat central sleep apnea.

Complex Sleep Apnea

Complex Sleep Apnea, sometimes known as Mixed Sleep Apnea, is a combination of obstructive sleep apnea and central sleep apnea.

People with complex sleep apnea have airways that become blocked when they are asleep as well as problems with the way that their brains regulate their breathing when they are asleep.

Sometimes, using a CPAP machine can cause someone with obstructive sleep apnea to develop central sleep apnea as well.  .

Symptoms of Sleep Apnea

Signs that you may suffer from sleep apnea include:

  • Extremely loud snoring. If you share a bedroom with someone, they may complain that your snoring is unusually loud. They may also notice that sometimes you stop breathing while you are asleep. Loud snoring is usually a symptom of obstructive sleep apnea. People with central sleep apnea do not usually snore very loudly
  • Waking up with a headache or sore throat
  • Feeling very sleep during the day, even when you think you have had a full night's sleep. You may develop the same symptoms as people who have severe insomnia, such as not being able to remember things very well or not being able to concentrate.
  • Because people with obstructive sleep apnea often stop breathing and then wake up during REM sleep, they can develop symptoms of REM sleep deprivation, including irritability, increased sensitivity to pain and difficulty forming long term memories, which can make it hard for them to learn things.
  • In some cases of obstructive sleep apnea, sufferers physically act out their dreams. Because their REM sleep is severely disturbed, their voluntary muscles never become paralyzed during REM sleep. This behavior mimics that of REM sleep behavior disorder.
  • Not being able to sleep through the night. If you have central sleep apnea, you may often wake up out of breath in the middle of the night.

Diagnosis of Sleep Apnea

  • If you exhibit symptoms of sleep apnea, you may be sent to a sleep lab to have a sleep study, or polysomnogram (PSG).When you have a polysomnogram, you sleep with sensors attached to you. These sensors are used to record your brain activity, your muscle activity, your heart rate, your blood pressure, your breathing and your blood oxygen levels throughout the night.
  • A doctor should check your throat, nose and mouth to see if you have any enlarged tissues that are blocking your air passage.
  • It may not be necessary to perform a sleep study on a child with symptoms of sleep apnea, as sleep apnea in children is usually caused by enlarged tonsils or enlarged adenoids.

Dangers of Sleep Apnea

Sleep apnea increases your risk of developing high blood pressure, developing abnormal heart rhythms, having a heart attack or having stroke because the constant drops in oxygen levels throughout the night are very hard on your cardiovascular system.

People with obstructive sleep apnea are more likely to suffer from insulin resistance or type 2 diabetes, than people who do not have obstructive sleep apnea, even if they are not overweight.  Scientists have been able to cause insulin resistance in mice by lowering their oxygen levels. This indicates that the lowered oxygen levels in people with sleep apnea can cause metabolic changes that lead to the development of insulin resistance or type 2 diabetes.

The sleep deprivation that is caused by sleep apnea can be extremely dangerous.  If you have sleep apnea, you may have difficulty concentrating when you are awake, and you may find yourself falling asleep when you should be alert. This can cause you to have accidents, endangering both yourself and the people around you.

For more information about the stages of sleep, see What Happens When We Sleep and Dream?