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Obstructive sleep apnea (OSA), a sleep-related breathing disorder characterized by recurrent episodes of airway obstruction during sleep that result in repetitive apneas and hypopneas, is a growing concern because an estimated 4% of men and 2% of women are affected by the condition worldwide.1 In addition to its pervasiveness, OSA's connection with an increased risk of workplace and traffic accidents and its association with increased morbidity from type 2 diabetes,2 cardiovascular disease,3 depression,4 and other chronic life-threatening conditions reinforce the condition's status as a public health epidemic.
OSA is most frequently diagnosed in men older than 40, especially those who are overweight or obese (ie, body mass index of 30 or above),5 with the majority presenting with classic OSA symptoms, such as excessive daytime sleepiness, loud snoring, and repeated episodes of gasping and choking during sleep. The condition is not exclusive to men, however, and can affect people of any gender or age group, including women and children.
In addition to the aforementioned symptoms, there are a host of other symptoms-many of which are often overlooked or misattributed to another condition-that may suggest the presence of OSA. Dental professionals can help identify some of these less obvious and often misattributed symptoms of OSA in their patients, which may actually suggest the presence of an underlying sleep-related breathing disorder. Too often, many of these symptoms are treated without comprehensive exploration or testing to identify whether or not their root cause is OSA. It's important to note that the list of signs and symptoms included in this article is representative of those most likely to be uncovered in a dental operatory, but it is certainly not exhaustive.
Headache
A relationship between headaches and sleep apnea has been recognized for a long time. In fact, the International Classification of Headache Disorders recognizes sleep apnea headaches as frequent morning headaches that last less than 4 hours and occur in the presence of a score of greater than or equal to 5 on the Apnea-Hypopnea Index (AHI).6 An apnea-related headache may present in the form of a migraine, a tension-type or cluster headache, or a nonspecific headache.7
In a 2010 study, pain researchers from Missouri State University revealed that sleep deprivation causes the body to increase production of the proteins that cause chronic pain. The study also demonstrated that these proteins reduce the body's pain threshold and can trigger migraine headaches.8
Other studies point to hypoventilation during sleep as a possible cause for morning headaches.9 Hypoventilation is a state in which the amount of air entering the lungs is insufficient and results in decreased oxygen levels and increased carbon dioxide levels in the blood. When an OSA sufferer stops breathing repeatedly during the night, his or her brain receives less oxygen. This causes the blood vessels in the head to widen and can trigger vascular headaches.
Depression
Major depressive disorder (MDD), also known colloquially as clinical depression, or simply, depression, is a common but serious mood disorder that causes severe symptoms that affect a person's thoughts, feelings, and daily life.10 MDD is more prevalent among patients with OSA than the general population. According to the National Institute of Mental Health, an estimated 7% of the general population is affected by MDD11; however, nearly 18% of those with OSA are affected by MDD.12
Many symptoms of depression and OSA overlap because repeated awakenings associated with a sleep-related breathing disorder make restorative sleep impossible and cause related problems, including sleep disturbance, fatigue, irritability, trouble concentrating, and headache.
Gastroesophageal Reflux Disease
Gastroesophageal reflux disease (GERD) is a common problem caused by the retrograde flow of stomach contents into the esophagus. The condition, which is characterized by symptoms such as acid regurgitation and heartburn, is a particular problem for patients with OSA, especially those with comorbid obesity. When compared with individuals without OSA, those with the sleep disorder exhibit a greater number of nocturnal GERD symptoms and events.13
Fortunately, GERD is often easily identified in the dental chair through the presence of enamel erosion, providing dentists the perfect opportunity to discuss potential sleep issues with their patients.
Sleep Bruxism
Sleep bruxism, or nighttime tooth clenching and grinding, rarely occurs in isolation without another condition influencing its presence, and one of the most common coexisting conditions is OSA. Nearly 1 in 3 adults who are afflicted by OSA clench their jaws and grind their teeth at night.14 In contrast, approximately 1 in 8 adults in the general population suffer from sleep bruxism.15
When a coexisting relationship is present, the successful treatment of sleep-disordered breathing, such as with continuous positive airway pressure (CPAP) therapy or an oral appliance, may also greatly improve or eliminate sleep bruxism.
Morning Congestion
People with OSA often complain about experiencing an incessant "stuffy nose." Several conditions, such as a deviated septum or seasonal allergies, can lead to nasal obstruction, and those with persistent nasal congestion are twice as likely to have OSA.16 The reason for this is that people with an obstructed nasal airway compensate by breathing through their mouths, which is believed to weaken the upper airway and aggravate OSA.
Nocturia
Nocturia, a condition in which individuals wake up frequently during the night to urinate, can signify numerous health-related disorders, including OSA. As with other less obvious symptoms of OSA, the relationship between nocturia and sleep-disordered breathing is still being researched and not fully understood. One hypothesis is that apneic events throughout the night trigger the heart to secrete atrial natriuretic peptide, a hormone that plays an important role in regulating blood pressure. This release not only reduces intravascular circulatory volume and blood pressure, but also stimulates kidney function, leading to increased urinary output.17
Dry Mouth
Although many of us occasionally wake up with chapped lips or feeling like we swallowed a wad of cotton, the prevalence of dry mouth (ie, xerostomia) upon awakening is significantly higher among patients with OSA.18In one study that included more than 1,200 adults, approximately 16% of those who snored and approximately 31% of those diagnosed with OSA reported experiencing dry mouth. By comparison, of those who did not snore or who were not diagnosed with OSA, about 3% reported experiencing dry mouth. OSA sufferers are more likely to experience dry mouth because they tend to breathe with an open mouth during sleep, which dries out the salivary glands.
Memory Loss
Multiple studies have demonstrated the relationship between sleep and memory function, particularly memory processing and consolidation, and have established that a lack of quality sleep causes not only memory loss but also structural damage to the brain.19It's no surprise then that many of those with OSA who suffer fragmented sleep and intermittent hypoxia report memory loss among their symptoms (Figure 1).
Furthermore, the presence of sleep-related breathing disorders such as OSA has been associated with the onset of cognitive decline at an earlier age20 as well as the worsening of and possibly even the pathogenesis of cognitive disorders such as Alzheimer's disease and dementia.21 Fortunately, the effective treatment of sleep disordered breathing may delay the progression of cognitive impairment.
Atrial Fibrillation
Atrial fibrillation (AF), which is frequently referred to as "AFib," is characterized by an accelerated and irregular heartbeat and is the most common cardiac arrhythmia.22 For adults, a normal resting heart rate ranges from 60 to 100 beats per minute; however, for an adult with AF, the heart rate may range from 100 to 175 beats per minute.
Studies have demonstrated a strong link between OSA and AF,23 and although OSA hasn't been proven to cause AF, the conditions share many common risk factors, with the most significant being obesity. In addition, both OSA and AF are associated with other serious and life-threatening conditions such as stroke and cardiovascular disease. The good news is that treating OSA can improve AF by reversing the cardiac functional and structural changes that are caused by the repetitive forced inspiration against a closed airway.
Hypertension
Hypertension, or high blood pressure, is commonly associated with an underlying condition such as OSA.24When rising blood pressure occurs in conjunction with an underlying condition, physicians call this secondary hypertension, and there is a myriad of research that points to OSA as an accessory to hypertension.25 Reasons for this connection likely involve the sustained, increased activation of the body's fight or flight response that is associated with episodic hypoxia.
Ultimately, elevated blood pressure coupled with other less-understood conditions, such as changes in intrathoracic pressure, oxidative stress, and vascular inflammation, may explain the increase in heart problems and risk of death among OSA patients. Although there is promising evidence that adequate treatment of acute OSA in patients with hypertension improves blood pressure levels, additional research is needed to more clearly identify the response specific to OSA treatment.
In patients with OSA and high blood pressure, the best treatment strategy presumably involves combining OSA treatment with blood pressure medication. This solution is likely to be more effective in lowering both nighttime and daytime blood pressure levels than either treatment alone. The result may be a considerable reduction in cardiovascular risk.
Discussion
As healthcare professionals, dentists are acutely aware of the importance of detecting the risk and/or onset of conditions before they have life threatening consequences. With the increasing prevalence of OSA worldwide, dentists have a responsibility to be on high alert for all potential risk factors and symptoms exhibited by their patients. This article discusses several often overlooked or misattributed signs of OSA, but this list is just scratching the surface. Dentists and other healthcare providers should be mindful of the relationship between oral health, physical health, and sleep so that they can drive the proper diagnosis and treatment of the root cause or causes of conditions rather than just treating symptoms.
Queries regarding this course may be submitted to authorqueries@aegiscomm.com
About the Author
Kent Smith, DDS
Diplomate
American Board of Dental Sleep Medicine
President
American Sleep and Breathing Academy
Private Practice
Dallas, Texas
References
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