Obstructive sleep apnea (OSA) is a common disorder where the upper airway becomes blocked during sleep, leading to breathing pauses known as apneas or reduced breathing known as hypopneas. These interruptions can lower blood oxygen levels and disrupt sleep, causing daytime symptoms like sleepiness and decreased cognitive function. Many individuals are unaware of their condition, with symptoms often noticed by a bed partner. OSA can have long-term effects on health and quality of life, including neurocognitive issues and a link to snoring and related disorders.

Signs and symptoms

Common symptoms of obstructive sleep apnea (OSA) include daytime sleepiness, restless sleep, and loud snoring with periods of silence followed by gasps. Less common symptoms encompass morning headaches, insomnia, trouble concentrating, mood changes like irritability and anxiety, forgetfulness, increased heart rate or blood pressure, decreased sex drive, unexplained weight gain, increased urinary frequency or nocturia, frequent heartburn or gastroesophageal reflux, and heavy night sweats.

OSA can occur transiently due to factors like upper respiratory infections causing nasal congestion and throat swelling, tonsillitis leading to enlarged tonsils, or acute infections such as severe infectious mononucleosis caused by the Epstein-Barr virus. Temporary OSA spells can also result from drug use, such as alcohol, which excessively relaxes the body tone and interferes with normal sleep arousal mechanisms.


Extreme daytime sleepiness stands out as the key symptom of obstructive sleep apnea (OSA) in adults. Typically, individuals with severe and long-standing OSA may experience brief episodes of falling asleep during routine daytime activities if given a chance to sit or rest, sometimes even during social interactions. Hypoxia linked to OSA can induce changes in neuronal structures like the hippocampus and the right frontal cortex, potentially affecting cognitive functions and contributing to conditions like Alzheimer’s disease. Diagnosis of OSA is often more prevalent among individuals in relationships, as partners may notice symptoms like loud snoring. However, there’s a stigma surrounding snoring, particularly in women, which may lead to underreporting or reluctance to seek treatment, such as Continuous Positive Airway Pressure (CPAP) therapy.


While excessive sleepiness, known as hypersomnolence, can occur in children with OSA, it’s less typical than in adults. Instead, young children with severe OSA often display behaviors resembling being over-tired or hyperactive, along with issues like irritability and attention deficits. Body characteristics differ between adults and children with severe OSA, with adults typically being heavier and having short, heavy necks, while children may exhibit failure to thrive due to breathing difficulties and obstructed eating. Obesity plays a significant role in pediatric OSA, leading to upper airway obstruction during sleep and contributing to its severity. Weight loss interventions have shown promise in reducing OSA symptoms in obese adolescents.

Risk factors.

Risk factors for obstructive sleep apnea (OSA) encompass obesity, age, muscle tone, medication and lifestyle choices, and genetic predispositions. Obesity contributes to OSA by increasing neck fat tissue, which can obstruct the airway during sleep. However, even individuals with normal body mass indices (BMIs) can develop OSA, possibly due to factors like decreased muscle tone or structural airway abnormalities. Sleeping in a supine position can exacerbate OSA due to gravitational effects and loss of throat and tongue tone during deep sleep. Treatment with continuous positive airway pressure (CPAP) can confirm airway collapse as the cause of OSA.

Throat lesions, such as enlarged tonsils, are recognized as aggravating factors for OSA, and their removal can provide relief. Aging often leads to loss of muscle tone in the upper airway, while lifestyle factors like smoking and alcohol consumption can increase OSA risk by inflaming upper airway tissues or relaxing muscles. Medications that induce sleepiness or muscle relaxation also contribute to OSA development or worsening.

Genetic factors play a role in OSA susceptibility, with individuals having a family history of OSA being more likely to develop the condition themselves. Additionally, conditions like allergic rhinitis and asthma can increase the frequency of OSA.


Obstructive sleep apnea (OSA) syndrome occurs when a patient exhibits recurrent instances of upper airway collapse during sleep, resulting in apneas or hypopneas. The criteria for defining these events can vary. Hypopnea is characterized by a reduction in airflow of at least 30% lasting a minimum of 10 seconds and associated with a decrease in pulse oxygenation of at least 4%, or a reduction in airflow of at least 30% lasting at least 10 seconds, associated either with a decrease in pulse oxygenation of at least 3% or with arousal.

OSA syndrome is diagnosed if the Apnea-Hypopnea Index (AHI) exceeds 5 episodes per hour and leads to daytime sleepiness and fatigue, or if the Respiratory Disturbance Index (RDI) is 15 or higher, regardless of symptoms.

AHI Rating
< 5 Normal
5–15 Mild
15–30 Moderate
> 30 Severe

Polysomnography (PSG, sleep study)

Night-time in-laboratory Level 1 polysomnography (PSG) serves as the primary diagnostic test for obstructive sleep apnea (OSA). During PSG, patients undergo monitoring using various sensors including EEG leads, pulse oximetry, temperature and pressure sensors to detect airflow, respiratory impedance plethysmography, ECG leads, and EMG sensors to detect muscle contractions in different areas. A hypopnea can be defined by two criteria: a reduction in airflow of at least 30% for over 10 seconds associated with a 4% oxygen desaturation, or a reduction in airflow of at least 30% for over 10 seconds associated with a 3% oxygen desaturation or an arousal from sleep on EEG.

An “event” during PSG can be either an apnea, characterized by complete cessation of airflow for at least 10 seconds, or a hypopnea, where airflow decreases by 50% for 10 seconds or by 30% if accompanied by a decrease in oxygen saturation or an arousal from sleep. The severity of sleep apnea is graded based on the number of events per hour, known as the apnea-hypopnea index (AHI). An AHI of less than 5 is considered normal, 5–15 is mild, 15–30 is moderate, and more than 30 events per hour indicate severe sleep apnea.


regulates airflow and airway pressure:

  • CPAP
  • BiPAP

Modern devices also have a CSA detection sensor that can automatically by learning the patient adjust the airflow and the pressure.