For this we turned to Meir Kryger, M.D., professor of pulmonary and critical care at Yale School of Medicine, and sleep medicine specialist. He writes:
“Our nervous system is continuously bombarded with information that it uses to control the many processes that keep us alive and healthy and out of danger. For example it receives information from sensors that measure oxygen and carbon dioxide to regulate breathing.
“The brain also handles sensory information so that we can see, hear, feel, taste, and smell and are able to respond to these sensations. When we sleep, the brain continues to process vital information (for example, breathing is still controlled) but it ignores the information from the sensory organs. We are disengaged from our sensations. The information is still bombarding the nervous system, but brain centers actively filter the information.
“Thus a sleeper will not hear their own snoring even when it is loud, because the brain has decided that it will not react to the snoring noise. The noise is actively filtered so that the brain will respond to a new noise or an important noise (for example a baby crying).
“If the snoring turns to apnea (breathing stops) the information from sensors that include those that measure oxygen and carbon dioxide bombard the brain and the brain will awaken the sleeper, resulting in the resumption of breathing. If this ability to awaken to danger were not present, many people would die in their sleep.”