Obstructive Sleep Apnea and Heart conditions

Introduction:

Human beings spend approximately one-third of their lives sleeping. The last few decades witnessed a drastic growth in the clinical and basic aspects of sleep medicine. Sleep is no longer considered a passive and homogenous state. It consists of complex brain activity, behaviour, and physiology. Sleep breathing disorders such as sleep apnea are prevalent disorders in the adult population and are commonly associated with co-morbid conditions. Most common type of sleep breathing disorders includes obstructive sleep apnea, central sleep apnea and sleep-related hypoventilation.¹

What is obstructive sleep apnea?

Obstructive sleep apnea (OSA) is a sleep-related breathing disease that is becoming more prevalent. In OSA, during sleep, the pharyngeal airway periodically narrows and becomes obstructed. During sleep, the reduction in airflow often leads to acute derangements in gas exchange, recurrent arousals, activation of the sympathetic nervous system, and disruption in normal hormone secretion.²

There are several common sleep and daytime symptoms associated with OSA. During sleep, snoring is one of the most common symptom, and daytime symptoms include excessive sleepiness during day, fatigue, decreased cognitive performance, morning headache, irritability, and memory loss.^3,4

Despite the numerous advancements in the understanding and the pathogenesis and clinical consequences of OSA, great majority of patients (approximately 70%–80%) remain undiagnosed.⁵ The risk of OSA is greatly influenced by modifiable and non-modifiable factors. Unmodifiable factors include sex, race, genetic predisposition as well as cranio-facial anatomy. On the other hand, modifiable factors include obesity, medication, smoking, nasal congestion or endocrine disorders.³

Population-based studies have shown that symptomatic OSA affects approximately 3% to 7% of adult men and 2% to 5% of adult women.¹ It is found to be 1.5-2 times more common in men than in women and its prevalence increases with age and obesity. The screening for patients with suspected OSA starts with a thorough sleep history to identify symptoms, risk factors, and comorbid conditions, followed by physical examination for OSA-related features.³

Obstructive sleep apnea and heart diseases:

Studies have reported that heart disease is one of the leading causes of death in the United States and around the world. The risk of heart disease is increased by a number of factors, which include unhealthy dietary habits, lack of physical activity, excessive alcohol intake, and smoking. hypertension, unhealthy cholesterol levels, diabetes and obesity. Sleep breathing disorders, particularly OSA also significantly increases the risk of heart arrhythmias and cardiovascular disease. It has been reported that patients with sleep apnea are 2-4 four times more likely to develop heart arrhythmias (abnormal heart rhythms) than people without this condition. Sleep apnea increases the risk of heart failure by 140% and the risk of coronary heart disease by 30%.⁶ Several epidemiological and clinical studies have explored the association between OSA and heart disease as they share common risk factors such as age, gender, race and obesity.

OSA, obesity and heart conditions

Obesity is counted as one of the most common risk factor for the development of OSA as well as heart diseases. It is often associated with increased fat around the neck that narrows or block the upper airway while sleeping. It is crucial to remember that sleep apnea, whether alone or in combination with obesity, can raise the risk of heart disease. But an increase in 10% body weight accounts for increase in risk of OSA by six-fold. Sleep apnea alone or with obesity increases the risk of heart diseases like high blood pressure, increase in bad cholesterol levels, and diabetes.

Insufficient Sleep and heart health

Allowing the body to rest and reenergize is one of the most significant purposes of sleep. During sleep, your heart rate and blood pressure both decrease. Insufficient or fragmented sleep in conditions like OSA can negatively affect the heart health by not providing proper time for rest and recovery. Chronic sleep deprivation poses an increased risk for hypertension, heart attack and stroke.⁷

Effects of OSA on cardiovascular system

The recurrent pauses in breathing during an episode of sleep apnea can stress and damage not only heart but also the complete cardiovascular system. The negative impact of sleep apnea on heart is still an ongoing research, however several biological pathways have been suggested as linking sleep apnea to cardiovascular diseases. The pathways include:

Activation of sympathetic nervous system

In OSA, repetitive cessation of breathing during sleep cause decreased oxygen levels in blood, which leads to activation of specialized cells called chemoreceptors. These cells detect the changes, elevate the activity of sympathetic nervous system, the part of nervous system that responds to stress and anxiety. This triggers the body to gasp more air and wakefulness. Similarly, sympathetic nervous reacts to lower oxygen levels by constricting blood vessels, increase heart rate and blood pressure. Recurrent episodes of obstructive apnea throughout the sleep could cause repetitive changes in blood pressure and may lead to hypertension or can worsen the existing cardiovascular conditions. In patients, with moderate to severe OSA, it can lead to 25% rise in systolic and diastolic pressure.⁶

Intra-thoracic pressure changes

Inhalation occurs against a restricted or closed upper airway in people with OSA. These attempted forceful inhalations might result in significant changes in chest cavity pressure. The heart can be damaged by these repeated variations in intrathoracic pressure, which can lead to atrial fibrillation (an irregular, typically rapid heartbeat), blood flow difficulties, and even heart failure.

Oxidative stress

After each pause in breath, lack of oxygen causes formation of oxygen reactive species, during the phase of reoxygenation. This leads to an increase in oxidative stress, which promotes systemic inflammation along with neurochemical and physiological processes that raise the risk of heart disease.^6,8

Management of OSA to reduce risk of heart diseases

If a person is diagnosed with OSA, treatments are often effective and help in reducing the risk of heart diseases. Management of OSA includes:

Maintaining a healthy weight: Obesity is considered as one of the cause for OSA as well as cardiovascular diseases. Maintaining a healthy weight can help in management of OSA and in decreasing the risk of heart diseases.

Lifestyle modifications: Regular exercise can help in increasing the respiratory strength and helps in increasing the flow to lungs. Avoiding alcohol intake in the evenings can also help in reducing the symptoms of OSA during sleep and improve the daytime functions.

Positive pressure therapies: Continuous positive air pressure (CPAP) devices keep the upper airway from collapsing during sleep.
Surgery: In patients whose OSA is caused solely by anatomical compromise of the upper airway, surgical intervention may be considered, although it is rarely performed in adult patients.

Oral appliances: Customised dental or oral appliances are used to retain protruding jaw and to reposit or stabilize tongue while sleeping to prevent upper airway obstruction.

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