By Gerard Meskill, M.D.
A 29-year-old woman presents to the sleep clinic complaining of a chronic history of insomnia. She reports that while she has difficulty going to sleep due to racing thoughts going through her mind, the bigger problem is that she wakes up several times during the night, often occurring at the same times each night. Some of these awakenings involve going to the bathroom. It is increasingly harder to go back to sleep each time. She has tried multiple different sleeping pills, but none seem to solve her problem. She doesn't snore, but frequently when she wakes up, she has a dry mouth, is sweating, and sometimes her heart is racing. Occasionally, she notes that she has been clenching her teeth during sleep. Her husband says that occasionally she talks in her sleep. She also frequently wakes up in the morning with heartburn.
On physical exam, she has unremarkable vital signs and normal body weight. She has normal heart rate and breath sounds, an overbite, mild enamel wear on her front teeth, horizontal mid-level scars on each of her cheeks, teeth indentations on her tongue ("scalloping"), and modestly enlarged (2+) tonsils. It is difficult to see the back of her throat because of the position of her tongue.
She had two prior sleep studies performed. Both noted that it took a long time for her to fall asleep and that she had frequent arousals out of sleep, but it did not show any abnormalities in her breathing. However, each demonstrated intermittent leg movements during the night. She was told that she had chronic insomnia and was coached in behavioral techniques to improve her condition, such as going to bed and getting up at the same time each day, winding down at night before bed, turning off the television in the bedroom, and avoiding stimulating activities and electronic devices before bed. Additionally, she was given a prescription to use for her "Periodic Limb Movement Disorder." None of this worked, and her insomnia just kept getting worse.
A third sleep study using more sensitive diagnostic tools demonstrated that the patient has Upper Airway Resistance Syndrome (UARS). Conventional sleep studies frequently miss the nuances of this disorder because patients with UARS do not always snore, do not have significant changes in their airflow during the night, and do not have significant drops in their oxygen saturation. These three are the classic signs screened for in Obstructive Sleep Apnea (OSA), but they are not always found in UARS (1).
Patients with UARS may suffer from a variety of symptoms, including excessive daytime sleepiness and/or fatigue, snoring, chronic insomnia (both going to sleep and going back to sleep after waking), frequent arousals out of sleep, nocturia (i.e., frequent episodes of getting up to urinate), bruxism (teeth clenching or grinding during sleep), TMJ pain, morning headaches, night sweats, parasomnias (sleepwalking, sleep talking, sleep paralysis, etc.), anxiety about sleep, depression, poor memory and/or concentration (including ADHD-like symptoms and "brain fog"), morning nasal congestion, and acid reflux/heartburn (2, 3).
Each of these symptoms can be explained by changes in human physiology during sleep. When a person goes to sleep, the body's muscles become more relaxed, including those of the jaw, the tongue, and the throat. This leads to the jaw and tongue sliding back, and the throat becoming less rigid. These changes make the diameter of the top of the airway narrower, requiring more effort to pull air into the lungs. This can lead to airflow turbulence, creating vibration of the soft tissue in the airway. This sometimes produces sound (i.e., snoring) and can lead to mucosal irritation and mucous production during the night. The body compensates for this airway narrowing by increasing chest expansion, which generates a stronger vacuum force in the chest to pull the air into the lungs. In OSA, the soft tissue at the top of the throat may collapse due to this vacuum, closing the airway. In UARS, this does not happen, and the airway stays open. However, the relatively narrow opening leads to sustained increased effort to breathe during the night. The body sometimes thrusts the jaw forward and clenches it in place in order to keep the tongue forward to widen the diameter of the top of the airway. This thrusting is the source of teeth grinding, while the clenching can lead to significant muscle soreness and headaches.
Meanwhile, the sustained increased respiratory effort to pull air through a narrower opening is interpreted as abnormal by the peripheral nervous system, leading to strong signals being sent to the brain that cause brief disruptions in sleep. These disruptions interrupt the normal sleep cycle, reducing the efficiency of the brain's restorative process and therefore can lead to daytime sleepiness and fatigue, as well as impaired concentration and memory.
The vacuum pressure generated in the chest also increases the work needed for the heart to contract, which can lead to a reduction in the amount of blood ejected from the heart. Over time, this can lead to mild swelling of the right side of the heart, which influences the heart to release factors into the bloodstream that signal the kidneys to waste fluid to reduce the volume entering the heart. This can lead to more frequent trips to the bathroom due to increased urine production (4).
This vacuum pressure also can lead to acid being pulled up from the stomach and into the esophagus, leading to heartburn at night. Certain stages of sleep (especially Rapid Eye Movement, or REM sleep) are more prone to airway restriction than others, and thus there may be predictable timing of awakenings during the night. The increased effort may lead to elevated heart rate and sweating, as well.
Unfortunately, not all sleep centers screen for more subtle signs and symptoms of obstructive respirations during sleep. Since the airflow may not change due to compensatory mechanisms to maintain the patency of the airway, conventional measurement of airflow pressure isn't always enough. The gold standard for measuring increased respiratory effort is esophageal manometry (Pes), a catheter used to observe the changes in chest pressure to detect periods of increased respiratory effort that lead to disruptions in sleep continuity (5).
Once diagnosed, a patient like the one in the vignette above would be given options for treating her condition, such as CPAP therapy, oral appliance therapy, and surgical interventions. Each of these options works in a different way to improve airway resistance to normalize nocturnal breathing, which then leads to more continuous and restorative sleep. So if you or someone you know has some of these symptoms described above, a sleep evaluation may be your ticket to a better night's sleep!
Sources:
1. Guilleminault C, Eldridge F, Dement WC. "Insomnia with sleep apnea: a new syndrome." Science 1973,181(4102):856-858.
2. Guilleminault C, Stoohs R, Clerk A, Cetel M, Maistros P. "A cause of excessive daytime sleepiness. The upper airway resistance syndrome." Chest 1993;104(3):781-787.
3. Kryger MH, Roth T, Dement WC. Principles and Practice of Sleep Medicine 5th Edition.
4. Umlauf MG, Chasens ER, Greevy RA, Arnold J, Burgio KL, Pillion DJ. "Obstructive sleep apnea, nocturia, and polyuria in older adults." Sleep 2004,27(1):139-144.
5. Shepard JW Jr, Gefter WB, Guilleminault C, Hoffman EA, Hoffstein V, Hudgel DW, Suratt PM, White DP. "Evaluation of the upper airway in patients with obstructive sleep apnea." Sleep 1991,14(4):361-371.
Gerard Meskill, M.D. is a board-certified neurologist who specializes in the treatment of sleep disorders. He completed his sleep fellowship training at the Stanford Center for Sleep Sciences and Medicine. He now practices sleep disorders medicine and neurology in the Greater Houston area at Comprehensive Sleep Medicine Associates, with offices in the Woodlands, the Houston Medical Center, and Sugar Land, Texas. For more information, visit http://www.houstonsleep.net.