What are the symptoms of obstructive sleep apnea (OSA)?
One of the most common Google Internet searches regarding sleep apnea is, "What are the symptoms of obstructive sleep apnea?" The symptoms of obstructive sleep apnea in adults are numerous and diverse. They can be roughly divided into "cardinal" (classical symptoms of the disorder), sleep quality-related, and daytime symptoms. Sleep apnea can present differently in certain populations, and symptoms can be alternatively characterized by the distinct manifestations in men, women, children, and elderly patients. In the first article in this series, the cardinal symptoms of obstructive sleep apnea (OSA) will be reviewed. Answer the following questions to assess your current knowledge of the topic:
- Which of these are considered cardinal symptoms of OSA? Select all that apply: a. chronic snoring b. trouble falling asleep c. night sweats d. gasp arousals (when you wake up gasping for air) e. witnessed apneas (someone witnesses you stop breathing in your sleep) f. restless sleep
- Which of these symptoms is the least common in sleep apnea sufferers a. chronic snoring b. witnessed apneas c. gasp arousals
- Which of these symptoms is most specific for sleep apnea? a. chronic snoring b. witnessed apneas c. gasp arousals
- Which of these symptoms is the most common in sleep apnea sufferers? a. chronic snoring b. witnessed apneas c. gasp arousals
Read on to find out the answers.
Sleep medicine doctors refer to chronic snoring, witnessed apneas and gasp arousals as the cardinal symptoms of sleep apnea. Let's get granular with what is meant by these terms.
What is snoring? Snoring refers to the audible, "rhonchorous" (coarse, rattling) breathing sounds that result from sleep-related anatomical restriction. Snoring is caused by the physics of fast-moving, turbulent air passing through a narrow tube, much like the vibratory effect that is heard when one blows through a plastic straw. In the case of snoring, the upper airway becomes a narrow tube and the tissues that form the tube, i.e. the soft palate and uvula, vibrate to produce the characteristic sound. Snoring can be disruptive to bed-partners' sleep (what's called "socially disruptive snoring") and sometimes people can wake themselves up with "snore arousals" (also called "snort arousals"). Scientific research has documented some loud snoring at over 100 decibels (dB), a level associated with hearing impairment. Chronic snoring can lead to mechanical irritation of the uvula and soft palate, causing these tissues to become edematous (swollen). This edema or swelling, in turn, results in greater airway obstruction, creating a vicious circle. In order to overcome the partially obstructed upper airway, the "bellows" of the lungs in the chest must work harder to maintain respirations. This force leads to traction on the uvula and soft palate and subsequent elongation, also contributing to greater obstruction. Some sleep apnea patients may experience waking up with the uvula having elongated greatly during the night, to the extent that it rests on the tongue. Sleep apnea treatment, such as CPAP, typically leads to improvement in the abnormal size and elongation of the uvula.
Certainly, not everyone who snores has obstructive sleep apnea. When snoring is observed on a sleep apnea test but the patient does not meet criteria for obstructive sleep apnea, the diagnosis is usually referred to as "primary snoring." By the same token, not everyone who has sleep apnea will present with a history of snoring. Often this is because patients do not have a consistent bed-partner, the bed-partner is hard of hearing, or the partner is a very "deep" sleeper. In certain populations, like overweight or obese pre-menopausal women, snoring may only occur minimally and later in the night, which often leads to sound-sleeping bed-partners being unaware of it.
Can snoring occur while awake? No, although people can have rhoncorous breathing sounds while awake that can be difficult to distinguish from snoring. Also, snoring can start immediately when someone enters stage N1 (light) sleep; the snorer may not even be aware that he or she had fallen asleep in this stage of sleep. One might wonder why sleep is essential for snoring: sleep onset is associated with decreased muscle and hypoglossal (tongue) tone, which promotes narrowing of the upper airway.
How is snoring defined as "chronic?" To be considered chronic, the snoring should occur during the majority of the nights of the week. Snoring does not have to occur every night and it does not have to be particularly loud to be associated with sleep apnea. Also, snoring does not have to be continuous and last all night to be a risk factor. In fact, most people with sleep apnea do not snore constantly.
Other Sleep-related Sounds
Snoring is not to be confused with stridor. Stridor is an abnormal breath sound that is high-pitched and musical. It is caused by obstruction of the upper airway at the level of the trachea, supraglottis, glottis or subglottis. Stridor can be characterized as inspiratory, expiratory, or biphasic. It is more common in the pediatric population and is associated with a number of medical problems, some of which are dangerous, such as epiglottitis (inflammation of the epiglottis). When detected, stridor should be evaluated by an otolaryngologist (ENT doctor) with direct visualization of the larynx via laryngoscopy.
Catathrenia is sometimes be confused with snoring. Catathrenia, also known as "sleep moaning" or "sleep groaning," is much less common than snoring. This is essentially a high-pitched, stereotyped vocalization that occurs during expiration. This is different from snoring, which is more prominent during the inspiratory phase of breathing. Catathrenia is categorized as a "parasomnia," or sleep-related movement disorder.
The Merriam-Webster Dictionary lists the etymology of the word apnea as from the Greek "a-" ("not") and "pnein" ("to breathe"). People often ask, "What defines a witnessed apnea?" A good rule of thumb is that a pause in breathing of more than 5 seconds is abnormal. On sleep studies, an apnea must last at least 10 seconds to be "scored" as an apnea. However, it is difficult, if not impossible, for one to accurately estimate with the naked ear and no stopwatch just how long the pauses are. Scientific research indicates that a history of witnessed apneas is associated with a positive predictive value, or the likelihood of having a disease prior to testing, of about 80%.
Usually, bed-partners find the pauses so alarming that they overestimate their length, often by two- to threefold or more. It is quite common for bed-partners and patients to present to sleep clinic highly anxious about the possibility that the patient will have an apnea and "not start breathing again." Reassurance is needed in this situation. While obstructive sleep apnea is associated with an increased risk of sudden death (with one large study showing OSA being associated with double the risk of sudden death) the overall rate of sudden death in this population is extremely low. It should be explained to patients that sleep apnea is a chronic medical problem, much like hypertension (high blood pressure) and diabetes that will lead to other medical problems, worse health outcomes, and decreased quality of life if not treated on a long-term basis. Technically, witnessed apneas are a "sign" as opposed to a symptom; signs are objectively observed by others while symptoms are subjective complaints. This distinction is generally made by medical professionals, not the lay public.
"Gasp arousal" refers to an episode of waking up gasping for air. A bed-partner observing such an episode, even if the sufferer doesn't recall it the next morning, also would count as a gasp arousal. This is the least common of the cardinal symptoms of obstructive sleep apnea. Often, arousals due to coughing, choking, and shortness of breath represent variations of gasp arousals and are attributable to underlying sleep apnea. However, these symptoms may have alternative medical disorder explanations, such as acid reflux (GERD), and certain heart diseases as well as pulmonary disorders. It is important to have a sleep doctor consultation to help distinguish among the potential causes of the symptoms and determine the need for further medical workup.
Gasp arousals are the rarest of the cardinal symptoms of obstructive sleep apnea and typically manifest as the disorder progresses and becomes more severe. People occasionally describe awakening from dreams of drowning or being suffocated, which likely represent another permutation of this symptom.
Remember, you can't diagnose sleep apnea from symptoms alone; if you think you might be at risk, a sleep apnea test is essential to rule obstructive sleep apnea in or out, determine the degree of sleep apnea, which dictates treatment options, and evaluate for other forms of sleep apnea (such as central sleep apnea).