What is Anxiety?
Anxiety is a state of fear, dread and uneasiness, typically elicited by life stressors such as health, money, work or relationship problems [1]. It’s a normal human experience, and under acute or long-lasting stress, it can be beneficial, mobilising your energy or helping you to focus on what’s important [2]. However, when these feelings of fear or nervousness become more persistent and distressing and interfere with day-to-day activities, they might be considered an anxiety disorder [1]. Roughly one in three adults will experience an anxiety disorder at some time in their life.
Causes of Anxiety
There is still no clear understanding of the cause of anxiety, but most commonly, there could be a coupled interaction between the following factors [2, 3]. Stress, other medical issues such as depression or diabetes, having first-degree relatives with generalised anxiety disorder, and mental health issues like child abuse, substance use, surgery and occupational hazards can trigger anxiety [2]. Recent research suggests that gut microbiome may affect anxiety.
Since anxiety is thought to originate in several parts of the brain, which include components of memory and the fear mechanism, this all could contribute to the feeling of anxiety [2]. We also know anxiety can be genetic or caused by environmental factors such as trauma, childhood stress and/or major negative or stressful life events [1].
Sometimes, it might be driven by a medical condition and could be the first manifestation of a physical rather than mental disease [4]. Either traumatic events or developmental factors, such as genetic ones, can increase the risk of anxiety [4].
What is Sleep Apnea?
Sleep apnea is an extremely common disorder in which breathing stops briefly numerous times during the night. Each apnea may last from a few seconds to several minutes, and the person can experience 30 or more of them in an hour. The result is poor-quality, frequently fragmented sleep and, possibly, heightened health risks [2, 1, 3]. The two main forms of sleep apnea are obstructive sleep apnea (OSA) and central sleep apnea (CSA). OSA results from the upper airway collapsing or becoming obstructed during sleep. In contrast, CSA originates when the brain fails to send the right signals to breathing muscles [5, 6, 7].
Causes of Sleep Apnea
Sleep apnea causes are multifaceted and can be attributed to various factors.
The muscle relaxations of sleep, for instance, lead to a narrowing or closure of the airway in cases of obstructive sleep apnea, either because the throat muscles are too relaxed or a relaxed tongue is unstable and ordinarily protective muscles fail to return it to the roof of the mouth, or the tongue enlarges to partly block the airway, or significant enlargements of the tonsils and adenoids occlude the passage of air. Likewise, obesity is a clear risk, perhaps by decreasing the cross-sectional size of the pharyngeal airway (where the muscles of the throat meet) near the top openings of the voice box. Other risk factors include irregular functioning of brain signals that control the throat muscles and the head and neck shape [8, 9, 10, 11, 12, 13, 14].
In contrast, the root cause of central sleep apnea is disruption of brain signaling that normally controls regular breathing, possibly due to brain and nervous system problems, including damage to the brainstem or prescription medication use, although congestive heart failure or stroke can also play a role [12, 7].
Lifestyle factors are also known to increase the risk of developing sleep apnea, including being overweight, male, having a family history of sleep apnea or small airways, and having bad habits such as smoking and drinking alcohol [5, 8, 15, 6].
Can Anxiety Cause Sleep Apnea?
The connection, it turns out, is complex and bidirectional. Although evidence points to the effects of sleep apnea on anxiety, it’s less clear that anxiety is indeed a cause of sleep apnea.
Repetitive episodes of oxygen-depleted breathing during sleep, a hallmark symptom of sleep apnea, have been connected to ongoing anxiety in more than one study. For example, in a study, increasing the Apnea-Hypopnea Index (AHI) by one unit was associated with an 18% increase in the likelihood of being allocated to the FOA group [16].
Yet, the evidence that anxiety causes sleep apnea is more circumstantial. Anxiety disturbs sleep by itself, causing symptoms such as insomnia and daytime sleepiness, both of which are prominent in sleep apnea [17]. These symptoms do not necessarily indicate sleep apnea.
In mice, models of sleep apnea, known as intermittent hypoxia, did not result in increased anxiety-like behaviour. When exposed to intermittent hypoxia for four hours a day for 14 days, the mice showed less anxiety-like behaviour than controls [18].
Conclusion
To conclude, there is a strong correlation between sleep apnea and anxiety, but there remains no evidence that anxiety can cause sleep apnea. More evidence is needed to determine whether causation can be inferred.