Sleep apnea (also spelled "apnoea") occurs when breathing stops while sleeping. These breathing interruptions are known as "apneas" and usually last for 10 seconds or more, many time over the course of the night. People who suffer with sleep apnea may wake up many times throughout the night, struggling to catch their breath.

There are 3 types of sleep apnea - obstructive sleep apnea (OSA), central sleep apnea (CSA) and mixed sleep apnea. OSA is by far the most common of these.

With OSA, the soft tissue at the back of the throat relaxes more than normal and blocks the airway. Breathing then requires considerable effort, and it is difficult to get air to the lungs. This leads to a decrease in oxygen levels in the blood.

Central sleep apnea is not that common. It occurs because the brain is not able to send the proper signals to body to regulate its breathing. Mixed sleep apnea is a combination of OSA and CSA but has more in common with OSA, including treatment methods.

People who suffer with sleep apnea are often tired during the day. They don't get enough rest over the course of the night because of a combination of the drop in blood oxygen levels, pauses in breathing and the struggle to get air to the lungs.

When they fall into a deep sleep, they will be pulled out of it when they have an apnea episode. This can happen many times over the course of a single night, resulting in a lack of quality rest.

People who suffer from sleep apnea are often loud snorers, but that's not to say one is a symptom of the other. Not all snorers are suffering from sleep apnea, and not all sleep apnea sufferes snore.

In most cases, people are not aware of their sleeping problem until it's brought to their attention by someone else. Their sleeping partner's rest often suffers as well, and they are usually the person who notices it first.