Introduction
Atrial fibrillation is the most common type of cardiac arrhythmia, whereas obstructive sleep apnea is a substantial breathing abnormality during sleep apnea. Both commodities are significant risk factors for stroke, and both diseases are linked with increased mortality. This article assembles the latest evidence on the role of sleep apnea on atrial fibrillation and vice versa.
What Is Atrial Fibrillation?
Atrial fibrillation is the most prevailing cardiac arrhythmia (the abnormal rhythm of the heartbeat) and carries significant mortality, morbidity, and healthcare costs. The occurrence of atrial fibrillation increases with age. Moreover, atrial fibrillation is associated with structural heart conditions and extra-cardiac factors, such as diabetes, hypertension, obesity, and sleep apnea. A person with atrial fibrillation has a fivefold higher risk of stroke and a twofold higher risk of cardiac-related death.
What Is Sleep Apnea?
Sleep apnea is described as intermittent cessation or weakening of breathing for at least ten seconds during sleep, resulting in oxygen desaturation. It is a breathing disorder during sleep where breathing becomes critically shallow or stops. There are two types of sleep apnea.
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Obstructive Sleep Apnea:
It is the most common type and is caused by a partial or complete collapse of the airway in the throat.
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Central Sleep Apnea:
It results from a reduction or absence of sufficient respiratory effort.
The estimated prevalence is about one in five adults having at least mild obstructive sleep apnea and one in 15 having moderate to severe obstructive sleep apnea.
What Are the Risk Factors of Sleep Apnea?
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Atrial fibrillation.
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Abnormalities of the upper airway soft tissue.
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Older age.
What Is the Link Between Sleep Apnea and Atrial Fibrillation?
Obstructive sleep apnea and atrial fibrillation share many common risk factors, and the prevalence of both is increasing, likely due to growth in cardiovascular disease and obesity. The close association between atrial fibrillation with cardiovascular disease and sleep apnea with cardiovascular disease may obscure a direct causal relationship between sleep apnea and atrial fibrillation.
Both chronic diseases are associated, and the interplay of their mechanism is complex and likely bidirectional. Sleep apnea may promote atrial fibrillation and vice versa. Nevertheless, there is extensive evidence that these entities are interlinked.
What Is the Mechanism by Which Sleep Apnea Causes Atrial Fibrillation?
Although the evidential support contributing to the association between sleep apnea and atrial fibrillation remains uncertain, numerous likely mechanisms are proposed, such as explained below;
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Sleep apnea can generate changes in cardiac function and structure. During sleep apnea episodes, repetitive forced inspiration against the closed airway results in negative pressure inside the chest cavity. That may result in increased cardiac afterload, atrial size, and stress on the heart's walls, which may result in atrial remodeling, making it prone to arrhythmia.
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Severe intermittent lower oxygen levels, high carbon dioxide levels, and higher acid levels in the blood result in some nervous system dysfunction leading to increased heart rate, blood pressure, and depression. This can persist in the daytime with normal oxygen levels; hence the effect may outlast the apneic episode. In addition, chemical substances released during lower oxygen levels in the blood may cause long-term damage to vessels and increase the tendency to develop hypertension. Lower blood oxygen levels may also trigger inflammation. All these circumstances lead to increased arrhythmia susceptibility.
What Is the Link Between Sleep Apnea and Atrial Fibrillation in Stroke?
Determining the cause of stroke is vital to reduce the risk of a subsequent event. Various studies identified atrial fibrillation as a likely cause of stroke in persons with sleep apnea. The results emphasize a high level of suspicion for atrial fibrillation in patients with sleep apnea and stroke.
What Is the Link Between Sleep Apnea and Atrial Fibrillation in Obesity?
Obesity is possibly one of the links between sleep apnea and atrial fibrillation. People who are obese have shorter sleep duration and have twice the subjective sleep problems compared to others. Obesity can result in cardiac remodeling.
What Is the Impact of Treatment of Sleep Apnea on Atrial Fibrillation?
Some studies have established that continuous positive airway pressure can reduce cardiovascular risk. Sleep apnea treatment with continuous positive airway pressure diminishes the risk of recurrent atrial fibrillation. The presence of untreated sleep apnea in individuals after cardioversion (a medical procedure that uses low-energy shocks quickly to restore regular heart rhythms) is associated with an 82 percent risk of recurrence of atrial fibrillation within one year, that risk is around half in individuals who is treated for sleep apnea. In these studies, the recurrence rate of atrial fibrillation among sleep apnea-treated individuals was similar to that of persons without sleep apnea. This demonstrates that sleep apnea plays a role in preserving atrial fibrillation, which can be mitigated by treatment.
Is It Beneficial to Screen Individuals With Sleep Apnea for Atrial Fibrillation?
Sleep apnea acts as an independent risk factor for causing stroke, and atrial fibrillation is likely to play a role in developing stroke in patients with sleep apnea. Therefore, early detection of asymptomatic atrial fibrillation in populations already at higher risk for stroke, such as individuals with sleep apnea, can reduce the chances of stroke as it aids in initiating stroke preventive therapies such as anticoagulation. Moreover, primary stroke prevention for susceptible individuals with atrial fibrillation with anticoagulation costs much less than post-stroke management and care.
Is It Beneficial to Screen Individuals With Atrial Fibrillation for Sleep Apnea?
Current recommendations for sleep apnea screening are limited as the sensitivity and particularity of screening scales need to be better established. However, excessive snoring or daytime sleepiness may lead to polysomnography (sleep study to diagnose sleep disorders). Therefore, the clinician may prescribe this sleep study if the person snores and have other clinical features of sleep apnea, including witnessed apnea, morning headaches, frequent awakening, cognitive deficits, and other clinical findings, such as cardiac dysrhythmia, hypertension, cardiovascular, obesity, or cerebrovascular disease.
Treatment of sleep apnea and risk factor modification may improve the treatment of atrial fibrillation, providing better control of stroke risk factors. Additionally, it is known that sleep apnea can influence the efficacy of treatments and the recurrence of atrial fibrillation. Thus, it seems appropriate to conduct sleep apnea screening in an individual with atrial fibrillation risk factors to optimize atrial fibrillation treatment strategies.
Conclusion
The common mechanisms linked to sleep apnea and atrial fibrillation are complex and mediated by many mechanisms. Sleep apnea causes structural and electrical changes that make it prone to arrhythmia, including atrial fibrillation. Prevention is the key. Physical activity and weight loss can decrease atrial fibrillation burden and severity of sleep apnea. Thus, taking control of this changeable risk factor will have a prominent effect on the prevalence of both disorders.
