To fully understand sleep-related breathing disorders, their cause and their consequences, it is helpful to place them in proper context - sleep. Because sleep medicine is a young field, little is known about this mysterious one third of our life. However, much research is emerging about the critical importance of sleep for good health.

Analyzing human sleep stages shows how sleep and sleep-related breathing disorders may be related:

• Stage 1 sleep is called the "introduction into sleep". This stage is frequently observed by watching someone's head nod when they are listening to a dull lecture. This stage is marked by a slowing down of brain activity and a beginning of muscle relaxation.

• Stage 2 sleep is the official "beginning of sleep". In this stage of sleep, there is a further slowing down of brain and muscle activity. This stage is best described in the following manner: You have been asleep in bed for 15-30 minutes and the phone rings. While you may regret being bothered in your sleep, you are easily able to answer the phone and, unless you tell the person who called you that you were asleep, they would never know. You become quickly alert and are able to easily engage in conversation. Some people will have enough relaxation of muscles in the throat area in this sleep stage that the upper airway may start collapsing and snoring begins.

• Stage 3 and 4 sleep are collectively called "slow wave sleep". In slow wave sleep, brain and muscle activity decrease significantly. In fact, there is so much relaxation of the muscles in the throat that people who are susceptible to sleep-related breathing disorders start having real problems. In our example, you are now asleep in bed for 45 minutes and the phone rings. You fumble for the phone and finally answer it. Anyone calling you would immediately know that they have awakened you. You are groggy and find it difficult to engage in conversation.

• "REM sleep" or rapid eye movement sleep is the time of sleep when dreaming occurs. During REM sleep the brain is very active, and yet, with the exception of the heart and lungs, the muscles of the body are paralyzed. This muscle paralysis has significant implications for sleep apnea or sleep suffocation sufferers. Since they experience complete muscle relaxation or paralysis in REM sleep, their airways can easily completely collapse. Most importantly, these people have far more difficulty resuming normal breathing after the airway has collapsed.

Healthy Sleep versus Sleep Fragmentation

Those people who experience healthy sleep will cycle through the various sleep stages throughout the night. The average person will have four or five "cycles" of sleep with a vast amount of this time spent in slow wave and REM sleep. This very critical time allows the body to work to perform activities that don't happen efficiently or not at all during other times. Medical science is only beginning to understand the importance of sleep.

People with sleep-related breathing disorders suffer from sleep fragmentation. As their bodies attempt to go deeper into sleep, the upper airway collapse interferes with breathing, forcing the body to revert to lighter sleep stages to get air. This sleep fragmentation interferes with the replenishment of the immune system, the production of growth hormone and the regulation of glucose metabolism, among other things.

Not only is it important to get adequate hours of sleep, those hours must be "efficient" sleep for optimal health. Many people who sleep very poorly sleep for long periods of time in a futile attempt to access deeper sleep stages. Many people with sleep-related breathing disorders rarely dream since they spend little time in REM sleep.

Please continue with the snoring section.