Sleep Apnea Demystified – All you need to know

A range of conditions described by abnormal breathing during sleep is grouped in sleep-disordered breathing. In Sleep apnea most cases, it is associated with narrowing or obstruction of the upper respiratory airway and is usually presented either as abnormal respiratory patterns (episodic occurrence of apneas and hypoapneas) or insufficient ventilation of the airway during sleep. The Greek word apnea literally means ‘without breath.’ It is usually described as the cessation of airflow for at least 10 seconds or longer and the patient wakes up to take a breath. On the other hand, hypoapnea is defined as the partial obstruction of the upper airway characterized by at least 30% decrease in airflow for 10 seconds or more associated with reduced oxygen saturation and disrupted sleep.1 Sleep-disordered breathing includes a spectrum of diseases, including isolated primary snoring, sleep apnea, and sleep-related hypoventilation.2 This article mainly focuses on understanding sleep apnea, types, prevalence, causes, risk factors, signs and symptoms, diagnosis, treatment modalities and complications.

Sleep Apnea and its types:

Sleep apnea is an involuntary cessation of breathing that happens during sleep. These episodes of momentary, often cyclical, halting in breathing rhythm are sufficient to cause significant disturbances in sleep cycles and several health complications. Sleep Apnea is divided into three types depending upon the underlying causes and characterized by distinct symptoms and treatment.3 Sleep apnea

  • Obstructive sleep apnea (OSA):  OSA is a sleep breathing disorder characterized by recurrent episodes of partial or complete intermittent physical obstruction of the upper airway during sleep. The episodes of apnea during sleep are terminated by brief arousal or awakenings enabling the return of breathing.4
  • Central sleep apnea (CSA): CSA is presented by recurrent episodes of shallow or decreased breathing during sleep resulting from altered brain control of respiratory muscles leading to a decline in ventilatory effort.5
  • Mixed sleep apnea, a combination of Obstructive & central: mixed sleep apnea also called complex sleep apnea. In this type, a person presents with features of both OSA and CSA at the same time. by convention in most of the mixed apnea cases, if more than 50% of the breathing events are central in nature it is considered primarily as a CSA.6

How common is it?

OSA is found to be highly prevalent among the general population. Several population-based studies have reported that in working people aged between 30 to 60, the prevalence of symptomatic OSA is estimated to be approximately 3 to 7% in men and 2 to 5% in adult women. OSA is found to be 1.5 to 2 times more common in men than in women and its prevalence also increases with age.2,5

Central sleep apnea has been found to affect approximately 0.9% of adults and it is found to be more prevalent in Sleep apnea men than women.7

As the data suggests, the occurrence of OSA is more common in the general population than CSA. For this reason, when people talk about sleep apnea, they are usually referring to OSA.

Signs and symptoms of sleep apnea

OSA is relatively common in the general population, it can either be asymptomatic or present with snoring or pauses in breathing while sleeping, or excessive day-time sleepiness due to disturbed sleep at night.8 The clinical signs and symptoms of OSA ranging from common to rare are described as following:

Common (in >60%): 

  • Loud snoring
  • Excessive daytime sleepiness
  • Feeling of choking or shortness of breath at night
  • Restless sleep
  • Unrefreshing or disturbed sleep
  • Changes in mood
  • Decreased cognitive performance
  • Nocturia

Less common (10-60%): Sleep apnea

  • Morning headaches
  • Bed wetting
  • Reduced sexual drive
  • Sweating while sleeping
  • Symptomatic oesophageal reflux

Rare (>10%)

  • Recurrent arousals or insomnia
  • Coughing while sleeping

Causes and Risk factors:

Despite the advancements and rising awareness about sleep apneas as a common finding in clinical conditions, even today, 70% to 80% of those suffering from OSA remain undiagnosed.6 Here, we discuss key risk factors for OSA:

Age: literature has reported sleep apneas to vary considerably with age, with one peak happening in childhood around the age of tonsillar hypertrophy after which the rate of occurrence declines and until the rates progressively increase with older age, where the prevalence is reported to be 30% or greater.4

Gender: Studies have reported that men are at higher risk for the development of sleep apnea as compared to women. It has been suggested that there is 2 to 3 fold increased prevalence among men as compared to women.9 In addition to the difference in prevalence, the breathing pattern of men and women also differs. Women tend to have lower AHI in non-rapid eye movement sleep. The disordered breathing events in women have a shorter duration and are associated with less deoxygenation of blood than in men. The increased predisposition of men towards the disease is attributable to the difference in anatomy and properties of the upper airway.10

Obesity: Studies have reported that approximately 40 to 60% of cases of OSA are attributable to being Sleep apnea overweight. An increase in weight raises the susceptibility of upper airways to collapse due to increased mechanical loading and reduces the resting lung volume.9

Craniofacial anatomy: Several structural variations related to soft and hard tissues can alter the mechanical properties and functioning of the upper airway. Literature has reported that individuals with features such as retrognathia (backward positioning of the lower jaw), tonsillar hypertrophy, an enlarged tongue or soft palate, mispositioning of the upper or lower jaw, and decreased posterior airway space can narrow the upper airway dimensions and increases the risk of apneas and hypopneas during sleep.10

Habits (Smoking and alcohol use): smoking and alcohol consumption before bedtime has been considered as the possible risk factors for obstructive sleep apnea. Studies have reported an increase in the prevalence of snoring and OSA with smoking. Alcohol consumption has been shown to increase the collapsibility of upper airways and precipitate the episodes of apnea and hypoapnea while sleeping. Alcohol consumption before bed also prolongs the duration and severity of episodes of obstructive events.10

Sleeping position: Studies have reported sleeping in a supine position increases the risk of tongue falling back and can cause airway blockage.10

In central sleep apnea, breathing is affected differently than in OSA. Instead of obstruction of airway and cessation of breathing, in CSA the apnoeic event arises in the absence of the respiratory efforts. It involves the loss of signal from the brain to muscles of respiration leading to hyper and hypo ventilated states causing obstructed and shallow breathing. This further is associated with health disorders of the heart and brain.11

According to the American Association of Sleep Medicine (AASM): Criteria for patients at high risk for OSA and evaluated for OSA symptoms4 Sleep apnea

  • Obesity (BMI > 35)
  • Congestive heart failure
  • Atrial fibrillation
  • Treatment refractory hypertension
  • Type 2 diabetes
  • Nocturnal dysrhythmias
  • Stroke
  • Pulmonary hypertension
  • High-risk driving population
  • Preoperative evaluation for bariatric surgery


Polysomnography (PSG) is considered a Gold standard for the diagnosis of sleep apnea (for both Obstructive and central) in a laboratory setting. According to the International Classification of Sleep Disorders-3 (ICSD-3) and American Association of Sleep Medicine (AASM), the diagnosis of obstructive apnea requires either the signs or symptoms such as fatigue, insomnia, associated daytime sleepiness, respiratory disturbance, episodic apnea or the associated medical or psychiatric disorder such as hypertension, cardiovascular diseases, diabetes, cognitive dysfunction, mood disorder associated with five or more predominately obstructive breathing events per hour of sleep during the PSG. Alternatively, a frequency of obstructive breathing events ≥15/hour without or with associated symptoms or disorders also confirms the diagnosis of OSA.12

With the clinical diagnosis, overnight oximetry can be undertaken at home. In patients with OSA, a typical oximetry pattern shows a normal baseline oxygen saturation with intermittent dips and 4% oxygen desaturation index of more than 10 per hour, with fluctuations in heart rate. Oximetry is a relatively specific, but an insensitive measure of sleep apnea. This can be used as a home diagnostic tool in patients diagnosed with one or the other sleep related breathing disorders.8

Though there have been many developments in the pathogenesis and clinical complications of OSA, but around 70%–80% of cases still continue to remain undetected. The diagnosis of sleep apnea is generally confounded by Sleep apnea the fact that patients are often unaware of the importance of associated symptoms. Even if they can it is frequently reported by a bed partner or family member.1

Management of sleep apnea

Management of sleep apnea continues to evolve as no therapy has yet matched the ideals of optimal efficacy and universal acceptance. Management goals for sleep apnea include improvement in common symptoms like daytime sleepiness, quality of life, sleep quality, and reduced risk of cardio and metabolic risk as well as normalizing apnea hypoapnea Index (AHI) and oxygen desaturation values. Various treatment modalities for sleep apnea include:

Lifestyle modifications:

Maintain healthy weight: Obesity is listed as the most common risk factor for the development of sleep apnea. Controlling weight and maintaining a healthy body mass index is well demonstrated to reduce parameters of OSA such as AHI in uncomplicated cases of sleep apnea.11

Exercise and yoga: Regular exercise and yoga can help with the improvement of symptoms of sleep apnea, as it helps in increasing the energy level, strengthen the body and heart, improves respiratory strength, and increase the oxygen flow to the lungs.

Get rid of bad habits: Smoking tends to cause more difficulty in initiating and maintaining sleep. it has been reported to contribute to upper airway dysfunction during sleep due to the production of mucosal edema, inflammation, and an increase in resistance in the airway. Smoking cessation can help with the improvement of symptoms of airway obstruction and the severity of the episodic obstructive events. Similarly, studies have reported reducing the consumption of alcohol near bedtime can help with the reduction in sleep apnea Sleep apnea complications and improves daytime performance in patients with sleep apnea.6

Sleep position alteration: Obstructive events while sleeping in a supine position are commonly associated with position-dependent OSA. Alteration in sleeping position from supine to lateral is considered as an effective treatment in controlling the episodic events of OSA. Positional change therapy with other healthy modifications can be used in conjunction to achieve better results.11

Positive pressure therapies: Continuous positive air pressure (CPAP) applied through the nose was first adopted as an effective therapy for OSA. Positive air pressure technique has evolved a lot over the years, various types of machines and masks are available these days. This technique still stands as an effective method for lowering the parameters of OSA severity, including AHI, oxygenation desaturation index (ODI), and oxygen saturation (SaO2). CPAP is the treatment of choice for moderate to severe cases of OSA. In an appropriate setting, it’s an effective treatment and helps in improving daytime sleepiness and fatigue.6

Oral appliances: customized dental or oral appliances are also used to maintain a patent airway during sleep. They are generally used either on the protruding lower jaw or as tongue retaining devices increasing the airway space during sleep. These devices help in keeping the tongue in place and preventing it from occluding the upper airways at oropharyngeal and laryngopharyngeal levels.6

Surgery: In patients with OSA due to anatomic and obstructing lesions such as tonsillar hypertrophy, surgical intervention is considered as the most likely and effective management modality. In the absence of an identified anatomic cause as obstruction, there is no consensus for the role of surgical treatment in OSA.6

In CSA, treatment therapy is generally designed according to the type and severity of severity. This includes the treatment of the underlying disorder, pharmacotherapy for respiratory centre stimulation, and supplementation therapy with oxygen or CPAP.6


The complications of sleep apnea are sleep deprivation and shallow sleep with continual sleep interruptions. Sleep apnea Reduced quality and quantity of sleep are associated with a wide range of serious health consequences that affect a person physically, mentally, and emotionally, and thus, it is no wonder that sleep apnea is connected with various health issues. Due to the low oxygen levels in the body, untreated cases of sleep apnea can lead to various types of cardio and metabolic disorders including high blood pressure, heart attack, coronary artery disease, stroke, diabetes, and mood disorders.6


Sleep apnoea and other sleep breathing disorders are common causes of morbidity and mortality affecting a vast population. The symptoms of sleep apnea vary with age and level of severity. Continuous positive airways pressure is a relatively simple and cost-effective treatment for obstructive sleep apnoea with healthy lifestyle modifications. Sleep apnea can generally lead to disrupted sleep and is associated with a wide range of serious health consequences that affect a person physically, mentally, and emotionally.


Q1. What is sleep apnea?

A1. Sleep apnea is a sleep disorder characterized by abnormal breathing during sleep. people with sleep apnea have multiple episodes of pauses in breathing while sleeping. These temporary obstructive and shallow episodes of breathing can cause reduced quality of sleep and affect the body’s supply of oxygen, consequently leading to serious health complications.

Q2. Who are at risk for sleep apnea?

A2. Individuals with a family history of snoring, obese with BMI of 25 or more are at higher risk for the Sleep apnea development of OSA. Males have a higher predisposition for sleep apnea as compared to women and it increases progressively with age.

Q3. What are the main symptoms of sleep apnea?

A3. Sleep apnea is clinically presented by snoring, daytime sleepiness, restless and disturbed sleep, episodic awakenings, and insomnia. Since people with sleep apnea have disrupted sleep, they often have excessive daytime sleepiness and morning headaches.

Q4. What does AHI represent?

A4. AHI stands for Apnea-hypoapnea Index that measures sleep apnea severity. The AHI is the sum of the number of apneas (pauses in breathing) plus the number of hypoapneas (periods of shallow breathing) that takes place in each hour.

Apneas and hypopneas, mutually referred to as events, should last for a duration of minimum 10 seconds to be called as events.

The AHI is calculated by dividing the number of events by the number of hours of sleep.

<5 Normal (no Sleep Apnea)
5-15 Mild Sleep Apnea
15-30 Moderate Sleep Apnea
>30 Severe Sleep Apnea

Q5. I snore at night. Should I be worried?

A5. Snoring is one of the main risk factor or warning signs for developing obstructive sleep apnea (OSA). As snoring is related to multiple health problems, it is important to consult your doctor before ruining the sleep and health of your partner or roommates.

Q6. What aggravates sleep apnea?

A6. Obesity greatly increases the risk of sleep apnea. People with thicker necks might have narrower airways. Males in older ages have increased risk of sleep apnea. Consumption of alcohol and smoking also triggers incidents of sleep apnea.

Q7. What are the lifestyle modifications for sleep apnea?

A7. With the early diagnosis in acute stages of sleep apnea, healthy lifestyle modifications can help with the management:

  • Maintain a healthy weight. Sleep apnea
  • Regular exercise and yoga can strengthen your heart helping to improve sleep apnea.
  • Change your sleeping positing. Sleeping on the side can help with sleep apnea
  • Avoid smoking and alcohol
  • Use a humidifier

Q8. What is the best sleeping position for sleep apnea?

A8. Several studies have suggested sleeping on the side is potentially the best position to sleep in patients with sleep apnea. Sleeping on the side reduces the risk of obstruction of the airway by the tongue, makes airways more stable, less likely to collapse or restrict airways.

Q9. What are the treatment options for sleep apnea?

A9. Sleep apnea is usually treated with proper diagnosis and medical attention. The most common treatment option for sleep apnea is continuous positive airway pressure (CPAP). CPAP is delivered through a mask attached to a small CPAP machine that maintains continuous air pressure. The pressure keeps the airway open and prevents the cessation of breathing during sleep. Although CPAP is very effective at treating sleep apnea, other alternatives include apnea dental devices and surgery in severe cases.

Q10. What are the complications related to untreated sleep apnea?

Q10. Untreated cases of sleep apnea can lead to various types of cardio and metabolic disorders including high blood pressure, heart attack, coronary artery disease, stroke, diabetes, and mood disorders.


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