Understanding Obstructive Sleep Apnea (OSA): Causes, Symptoms and Diagnosis

Obstructive Sleep Apnea (OSA) is a prevalent and potentially serious sleep disorder that affects millions of individuals worldwide. This condition is characterized by repetitive episodes of partial or complete upper airway obstruction during sleep, leading to disrupted sleep and a host of potential health complications. 

In this blog post, we will explore the causes, symptoms, and diagnosis of OSA, referencing key studies and medical guidelines from reputable sources such as the American Academy of Sleep Medicine (AASM) and the National Institutes of Health (NIH). By better understanding OSA, individuals can take the necessary steps to seek appropriate treatment and improve their quality of life.

Definition and Prevalence

Obstructive Sleep Apnea (OSA) is a common sleep disorder affecting an estimated 22 million Americans, with many more cases likely undiagnosed (American Sleep Apnea Association, n.d.). OSA occurs when the muscles in the throat relax during sleep, causing the airway to narrow or become completely blocked, leading to interruptions in breathing. These pauses in breathing, known as apneas, can last from a few seconds to over a minute and can occur multiple times per hour, disrupting the normal sleep cycle and preventing restorative sleep.

Historical Background

OSA has likely affected humans throughout history, but it was not formally recognized as a distinct medical condition until the 20th century. In 1965, Dr. Charles K. Friedberg first described "obstructive sleep apnea syndrome" in a case report (Friedberg, 1965). However, it was not until the development of continuous positive airway pressure (CPAP) therapy by Dr. Colin Sullivan in 1981 that an effective treatment for OSA became widely available (Sullivan et al., 1981).

Types of Sleep Apnea

Although OSA is the most common form of sleep apnea, there are other types, including Central Sleep Apnea (CSA) and Complex Sleep Apnea Syndrome (CompSAS). CSA is characterized by a lack of respiratory effort due to a failure in the brain's signaling to the muscles that control breathing, while CompSAS is a combination of both OSA and CSA. This blog post will primarily focus on OSA, as it is the most prevalent and widely recognized form of sleep apnea.

Anatomy and Physiology

OSA occurs when the airway becomes partially or completely obstructed during sleep. The muscles in the throat, including the soft palate, uvula, and tongue, relax during sleep, which can cause the airway to narrow or collapse. In individuals with OSA, this relaxation is more pronounced, leading to repeated episodes of airway obstruction and disrupted breathing. The brain then senses the lack of oxygen and briefly rouses the person from sleep to reopen the airway, often resulting in a loud gasp or snort. These brief awakenings, known as arousals, disrupt the normal sleep cycle and can contribute to daytime sleepiness and other symptoms.

Risk Factors

Several factors can increase the likelihood of developing OSA. Some of the most common risk factors include:

Obesity:  Excess body weight, particularly around the neck, can put pressure on the airway and increase the likelihood of obstruction during sleep. According to the AASM, approximately 70% of people with OSA are overweight or obese (AASM, 2014).

Age:  OSA is more common in middle-aged and older adults, although it can occur at any age. The risk of OSA increases as people age due to a loss of muscle tone and an increased likelihood of obesity (Young et al., 2002).

Gender:  Men are more likely to develop OSA than women, with studies suggesting that men are two to three times more likely to be affected (Peppard et al., 2013). However, the risk for women increases after menopause, potentially due to hormonal changes that affect muscle tone and fat distribution (Young et al., 2003).

Family History:  Individuals with a family history of OSA have a higher risk of developing the condition, suggesting a potential genetic predisposition (Redline et al., 1995).

Alcohol and Sedative Use:  The use of alcohol and sedatives can relax the muscles in the throat, increasing the likelihood of airway obstruction during sleep (AASM, 2014).

Smoking:  Smoking can cause inflammation and fluid retention in the airway, increasing the risk of OSA. Studies have found that smokers are three times more likely to have OSA than nonsmokers (Wetter et al., 1994).

Medical Conditions:  Certain medical conditions, such as hypothyroidism, acromegaly, and polycystic ovary syndrome (PCOS), can increase the risk of OSA (AASM, 2014).

Common Symptoms

The symptoms of OSA can vary from person to person, but some of the most common signs and symptoms include:

Loud Snoring:  Snoring is a common symptom of OSA, although not everyone who snores has sleep apnea. Snoring associated with OSA is typically louder and accompanied by periods of silence followed by gasps or choking sounds.

Choking or Gasping during Sleep:  People with OSA may experience episodes of choking or gasping for air as their body briefly rouses from sleep to reopen the airway.

Daytime Sleepiness:  Individuals with OSA often experience excessive daytime sleepiness due to the repeated disruptions in their sleep cycle, which can lead to difficulty concentrating, irritability, and a decreased quality of life.

Morning Headaches:  OSA can cause morning headaches due to the repeated episodes of low oxygen levels during sleep, which can dilate blood vessels and cause headaches.

Cognitive and Mood Disturbances:  OSA can lead to cognitive difficulties such as memory problems and difficulty concentrating, as well as mood disturbances like depression and anxiety.

Health Consequences

If left untreated, OSA can have significant health consequences, including:

Cardiovascular Risks:  OSA is associated with an increased risk of high blood pressure, heart attack, stroke, and heart failure due to the repeated episodes of low oxygen levels and increased stress on the cardiovascular system (Somers et al., 2008).

Metabolic Syndrome and Type 2 Diabetes:  OSA has been linked to insulin resistance, glucose intolerance, and an increased risk of type 2 diabetes and metabolic syndrome (Pamidi et al., 2015).

Cognitive Impairment:  Chronic sleep disruption caused by OSA can lead to problems with attention, memory, and executive function, potentially affecting job performance and increasing the risk of accidents (Beebe et al., 2003).

Mental Health Issues:  OSA has been linked to an increased risk of depression and anxiety, potentially due to the effects of sleep deprivation and fragmented sleep on mood regulation (Peppard et al., 2006).

Workplace and Transportation Accidents:  Excessive daytime sleepiness and impaired cognitive function caused by OSA can increase the risk of workplace accidents, motor vehicle accidents, and other incidents related to poor alertness and attention (Tregear et al., 2009).

Medical Evaluation and History

Proper diagnosis is essential for effective treatment and management. Diagnosing OSA typically begins with a thorough medical evaluation and history. During this evaluation, a healthcare provider will ask about the patient's sleep habits, symptoms, and any potential risk factors for OSA. A bed partner or family member may be asked to provide information about the patient's snoring, breathing patterns, and any observed episodes of apnea during sleep.

Sleep Lab Testing

A sleep lab test, or polysomnography (PSG), is the gold standard for diagnosing OSA. This comprehensive test measures various physiological parameters during sleep, providing a detailed assessment of the individual's sleep patterns and disruptions.

In-Lab Polysomnography (PSG):  An in-lab PSG is conducted at a specialized sleep center under the supervision of a trained sleep technician. The test involves attaching sensors to the individual's head, face, chest, and limbs to monitor brain activity, eye movement, heart rate, blood oxygen levels, and muscle activity throughout the night. This data is used to identify sleep stages, arousals, and breathing abnormalities related to OSA.

Split-Night PSG:  In some cases, a split-night PSG may be recommended. This test combines diagnostic and therapeutic aspects of sleep apnea evaluation. The first half of the night is spent diagnosing OSA, and if significant apnea is detected, the second half of the night is spent adjusting and initiating continuous positive airway pressure (CPAP) therapy.

Home Sleep Testing 

(HST) offers a convenient alternative to in-lab PSG for individuals who prefer to undergo testing in the comfort of their own homes or have difficulty accessing a sleep center. HST may be less comprehensive than in-lab PSG, but it is still an effective method for diagnosing OSA.

Portable Polysomnography:  Portable PSG devices are compact and user-friendly, allowing individuals to self-administer the test at home. These devices typically measure fewer parameters than in-lab PSG, focusing on essentials such as airflow, respiratory effort, blood oxygen levels, and heart rate.

ApneaLink™ and WatchPAT™:  Devices like ApneaLink™ and WatchPAT™ offer simpler, more accessible options for OSA diagnosis. ApneaLink™ uses a nasal cannula and finger pulse oximeter to measure airflow, blood oxygen levels, and heart rate, while WatchPAT™ is a wrist-worn device that uses peripheral arterial tone (PAT) signals, snoring, and body position to assess sleep apnea events.

Additional Diagnostic Tools

Epworth Sleepiness Scale:  (ESS) The Epworth Sleepiness Scale is a subjective questionnaire that helps assess an individual's level of daytime sleepiness. While not a diagnostic tool on its own, it can provide valuable information to healthcare providers when evaluating a patient for OSA.

Physical Examination and Medical History:   A thorough physical examination and medical history can help identify risk factors and potential causes of OSA, such as obesity, family history, smoking, or craniofacial abnormalities.

Both sleep lab testing and home sleep testing offer viable options for diagnosing OSA, with varying levels of convenience and comprehensiveness. Individuals suspecting they have OSA should consult with a healthcare professional to determine the best diagnostic method suited to their needs.

OSA Severity Classification

Once OSA is diagnosed, its severity is typically classified based on the apnea-hypopnea index (AHI), which measures the number of apneas and hypopneas (partial blockages of the airway) per hour of sleep. The AASM classifies OSA severity as follows (AASM, 2014):

     - Mild: AHI of 5 to 14 events per hour

     - Moderate: AHI of 15 to 29 events per hour

     - Severe: AHI of 30 or more events per hour

Given the significant health consequences with untreated OSA, awareness and diagnosis is crucial for individuals experiencing symptoms. Proper evaluation and diagnosis is key to early detection and treatment of OSA, which can greatly improve a person's quality of life and reduce the risk of potentially severe health complications.

The Role of Treatment in Managing OSA

Once diagnosed, there are various treatment options available for managing OSA, including lifestyle changes, CPAP therapy, oral appliances, and in some cases, surgery. The appropriate treatment will depend on the severity of the condition and the individual's specific needs and preferences. By understanding the causes, symptoms, and diagnosis of OSA, individuals can take the necessary steps to seek appropriate treatment and improve their overall health and well-being.

References

American Academy of Sleep Medicine. (2014). International classification of sleep disorders, 3rd ed. Darien, IL: American Academy of Sleep Medicine.

American Sleep Apnea Association. (n.d.). Sleep apnea