Sleep apnea is a serious health condition characterized by impaired breathing as the body relaxes during sleep. While there are different types of sleep apnea, the common element is the fact that sleep is repeatedly disrupted due to impaired breathing. The typical cycle goes like this:
- A person afflicted with sleep apnea drifts off to sleep
- Breathing stops (apnea) or is significantly reduced (hypopnea)
- The brain determines there is insufficient oxygen and excess carbon dioxide in the body and triggers an arousal
- The arousal causes the sleeper to resume breathing while remaining consciously unaware of the episode
Sleep apnea sufferers experience the above cycle numerous times throughout the night. In severe cases, it can happen hundreds of times each night. The quantity and cause of the apneas and hypopneas determine the type of sleep apnea one has (obstructive, central, or complex/mixed). For a definitive diagnosis, a sleep study is required.
The technical term for a pause or temporary cessation from normal breathing during sleep is apnea. The term for a significant reduction in breathing is hypopnea. Apneas and hypopneas are used to determine the severity of one’s sleep apnea through a measurement standard called the apnea-hypopnea index or AHI.
The term apnea was derived from the Greek word apnous meaning breathless.
Oxygen Deprivation and Sleep Fragmentation due to Sleep Apnea Wreak Havoc on the Human Body
As we breathe, our lungs take in oxygen and expel carbon dioxide. Without oxygen we cannot survive, of course. Thankfully, our brains are equipped with a fail-safe which instinctively arouses us if we stop breathing during sleep due to sleep apnea. Unfortunately, this cycle of breathing cessations (causing chronic intermittent hypoxia) and automatic-arousals (causing sleep fragmentation) can have significant negative effects on health.
Chronic Intermittent Hypoxia
Hypoxia is a decrease of oxygen in the blood within the arteries to an abnormally low level. Chronic, intermittent hypoxia is the periodic transitioning between normal blood oxygen levels and abnormally low blood oxygen levels. Sleep apnea can cause this.
While the automatic arousals resulting from apneas and some hypopneas are a good thing in that they keep us from suffocating, sleep sessions become fragmented which is bad for us. The all-important deeper, restorative stages of sleep (i.e., REM, deep sleep) get interrupted or never achieved. This only compounds the problems caused by intermittent hypoxia. Surprisingly, the sleeper typically does not remember these automatic arousals and, therefore, can awaken after 7-8 hours or more of sleep wondering why they feel completely unrested.
Long Term Consequences of Sleep Apnea
A 2016 study published on the National Institutes of Health website concluded, in part:
OSA (obstructive sleep apnea) causes persistent cardiovascular, metabolic, and cognitive consequences as well as increased cancer risk. Animal and clinical data support a specific role for intermittent hypoxia in promoting changes at molecular, cellular, and tissue levels that explain the OSA consequences. The association of OSA to vascular, metabolic, genetic, and cognitive consequences may be explained by the interplay of several pathways including sympathetic overactivity, oxidative stress, pro-inflammation processes, and sleep fragmentation.Source: Sforza, Emilia, and Fréderic Roche. “Chronic intermittent hypoxia and obstructive sleep apnea: an experimental and clinical approach.” Hypoxia (Auckland, N.Z.) vol. 4 99-108. 27 Apr. 2016, doi:10.2147/HP.S103091
If not treated, sleep apnea can lead to life threatening illnesses such as diabetes, heart failure and stroke.
In the short term, it can degrade the quality of life through fatigue, headaches, depression and impaired memory and cognition.
Most Cases of Moderate and Severe Obstructive Sleep Apnea are Undiagnosed
Since people afflicted with sleep apnea do not remember most, if not all, of the arousals their bodies experience during sleep, many carry on with their daily lives completely unaware that they have this debilitating disease.
Studies show that the global prevalence of obstructive sleep apnea is in the range of 1 billion people with an estimated 80 percent of the moderate and severe cases undiagnosed.