Sleep apnea syndrome is a disorder characterized by frequent, brief pauses in breathing during sleep, resulting in reduced oxygen flow to the brain. The disorder occurs in 4% of the general population, most commonly in middle-aged men, and is a common cause of daytime sleepiness and cognitive dysfunction in the areas of attention, concentration, complex problem solving, and short-term recall. Sleep apnea is a serious medical problem because it is associated with increased rates of Motor vehicle accidents, hypertension, Depression, and mortality.
Sleep apnea is significantly more common in persons with SCI, especially those with Tetraplegia, among whom an estimated 25% to 40% have the disorder. A number of factors may contribute to this high prevalence. Obesity is relatively common in this population, and individuals with SCI are predominantly males. Both of these are known risk factors for sleep apnea in the general population.
Weakness of respiratory muscles may contribute to the problem, especially in persons with tetraplegia, because the muscles cannot easily interrupt episodes of apnea. The use of sedating antispasticity medications such as baclofen is also considered a potential risk factor because these drugs are known to slow down the breathing apparatus.
Several additional factors may predispose the SCI population to sleep apnea. The supine (lying on one’s back) sleeping position is known to markedly increase the rate of obstructive breathing episodes in the non-SCI population. Many individuals with SCI are unable to change position while in bed, which may result in increased time spent in the supine position.
Persons with tetraplegia often rely on neck and upper chest muscles to help with breathing because the diaphragm muscle may not have normal strength. These muscles become inactive during the rapid eye movement stage of sleep, further compromising the individual’s ability to breathe. Nasal congestion is also common in SCI due to disruption of the autonomic (automatic) nervous system, and this further obstructs the airway.
Sleep apnea is often successfully treated in the general population through weight loss, avoidance of the supine sleeping position, and use of continuous positive airway pressure (CPAP) therapy, which uses a mask that fits over the nose and is attached to an air pumping device.
Unfortunately, treatment in the SCI population is more difficult. So far, CPAP has not been accepted well by many persons with SCI, possibly because limited upper limb function makes repositioning or adjusting the mask difficult. In previous studies, persons with SCI who were able to tolerate the CPAP showed decreased frequency of apnea episodes and reported increased daytime alertness.
Researchers at the UW are completing a study of patients with SCI who also have sleep apnea. This study is measuring sleepiness and other symptoms of sleep apnea, and evaluating the types of treatment currently being used by patients. This is expected to lead to another study investigating a new treatment and comparing it to conventional treatment. (Patients will be recruited for this study at a future date. Watch for notices in the SCI Forum Bulletins.
Sleep apnea may be even more common in the newly injured SCI population since respiratory muscle weakness is more severe in the first several weeks following injury. A study is currently underway at the UW (see front-page article) to investigate the prevalence of sleep apnea in newly injured patients (within three to five weeks after injury) and the extent to which the resulting cognitive dysfunction interferes with Rehabilitation.
It is possible that adjusting to the CPAP early on in the rehabilitation process may improve tolerance of the device over the long run and help people avoid sleep apnea and its associated problems in the future. It also may help patients to participate fully in therapies and learn the information and skills needed to take care of themselves after leaving the hospital.
Stephen P. Burns, MD
For more information about sleep apnea, contact:
* American Academy of Sleep Medicine
6301 Bandel Rd. Suite 101
Rochester, MN 55901
Web site: www.aasmnet.org
* American Sleep Apnea Association
1424 K St NW, Suite 302
Washington, DC 20005
Web site: www.sleepapnea.org