They may not even mention head injuries to the doctors they visit regarding their sleep problems. And doctors may not take into account previous head injuries when interviewing them regarding their current sleep issues.
However, research continues to draw linkages between brain injuries and sleep disorders.
What is a concussion?
A concussion is a kind of injury to the head which is caused by force or trauma. It could be an external blow, or it could result from extreme shaking that jostles the brain from its place inside the skull. Common causes for concussions include sports injuries, falls, physical assaults, combat injuries, and car collisions.
Traumatic brain injury (TBI) describes the damage done to the brain as a result of a concussion, as well the damage caused by objects which have penetrated the skull.
Mild TBIs (also known as mTBIs) typically take the form of concussions. However, more acute TBIs occur when physical damages to the brain are far more severe: the tissue is torn or bruised, or the brain bleeds. Without prompt attention to these injuries, someone can suffer long-term damage or even die.
Still, calling a concussion a "mild" TBI does no service to the one suffering the condition, as concussions are still considered very serious and can still have long-lasting and negative results.
How can a concussion impact sleep?
A study published by Neurology last winter, and reported on by NPR last April, suggests that damage from head injuries can lead to sleep-wake disturbances that can last 18 months.
In severe concussions, the trauma may actually lead to torn circuits buried deep within the brain. Dr. Brian Edlow, a neurologist at Massachusetts General Hospital who wrote an editorial that accompanied the study, said "It's the disruption of these circuits that is believed to cause sleep-wake disturbances."
Other research has shown that the process of sleep and the processes associated with healing brain injuries seem to share overlapping brain circuitry.
Dr. Lukas Imbach, the author of the Neurology study, suggests his research points to "a quiet epidemic of sleep disorders among people with traumatic brain injuries." He warns that sleep disorders that linger after such an injury are likely to last at least 2 years, and maybe even longer.
What kinds of sleep disorders can result from head injury?
There are 4 main kinds of sleep problems that can occur at the result of TBI: hypersomnia disorders, sleep apnea, insomnia disorders, and circadian rhythm disorders.
While getting extra sleep following a recent head injury can be helpful for healing brain trauma, patients sometimes continue to be sleepy during the day long after their injury has healed.
When this happens, it is referred to as post-traumatic hypersomnia.
In some cases, however, TBIs can lead to narcolepsy with or without cataplexy, which is a disorder of hypersomnia in which the need to sleep is physically irresistible. It can lead to sudden collapses in muscle tone and sleep paralysis.
Hypersomnia disorders negatively impact activities of daily living, interfering with normal life for ordinarily functional people of all ages. Also, excessive sleepiness (by whatever cause) during the day figures prominently in on-the-job accidents and motor vehicle collisions, making it a significant public health problem.
A 2007 study published in the Archives of Physical Medicine and Rehabilitation showed associations between sleep apnea and increased impairment to both memory and sustained attentionin those suffering from TBIs.
Injury to the brain can damage to the mechanisms buried deep inside which regulate breathing while asleep. This can lead to the occurrence of apneas, or pauses in breathing, that result in critical drops in blood oxygen. Untreated sleep apnea is a dangerous, chronic health condition with avoidable consequences.
It's worth noting that these apneas could be central, caused by a miscommunication between the brain and the respiratory system that is the result of a TBI, or obstructive, caused by mechanical dysfunction of the upper airway while breathing during sleep, which could also be caused by physical damage from the TBI, such as whiplash.
Described as difficulty falling asleep, staying asleep, or maintaining sleep, insomnia disorder can develop following a head injury, and several studies over the last decade have shown that it is a prevalent post-TBI condition.
More recent research indicates that treating the insomnia can lead to improvements in other symptoms that might be related to the TBI, such as depression and post-traumatic stress disorder (PTSD) among military personnel suffering from head injuries.
Circadian rhythm disorders
Misaligned circadian rhythms can lead to unusual sleep-wake patterns that can make it difficult to live a normal life. Advanced sleep phase or delayed sleep phase syndrome describes sleep-wake schedules that are either too early or too late for typical day-night schedules.
A head injury can lead to chemical and mechanical dysfunctions that don't coordinate with our built-in circadian processes, which rely on things like light exposure, digestion, and other time-associated indicators to keep tuned into normal light-dark cycles.
The future of research for TBIs and sleep disorders
Scientists are working on ways to better screen for sleep-wake disturbances among patients with previous head injuries. While having every patient with a TBI undergo a sleep study is too costly a solution, the development of a screening instrument to identify those more likely to suffer from a sleep disorder following a brain injury may be a more useful approach
A national team of sleep and TBI experts, from the University of Maryland School of Medicine, is working toward this effort, combining a meaningful assessment strategy with research for sleep-related treatments to improve outcomes for mild TBI.
Dr. Emerson Wickwire, chair of the university team, told reporters in Science Daily that from their own research, "leaders in TBI identified four topical areas that may be potential pathways to improve outcomes in mTBI: neuroinflammation, neuropsychiatric disease, chronic pain, and of course, disturbed sleep."
Wickwire says sleep and brain injury appear to share several overlapping brain circuits.
"Structures damaged in brain injury may cause alterations in sleep/wake cycles," he said. "At the same time, sleep disturbances, which are reported by roughly half of people with brain injury, worsen quality of life, make treatment more difficult, and may well change the way the brain heals itself," he said.
Based on what we know about head injuries, a closer look at clinical sleep disorders such as insomnia,
obstructive sleep apnea, circadian rhythm disorders, and hypersomnia in the aftermath of TBI is warranted.
Wickwire suggests that treatments for these sleep disorders in uninjured patients may need some adaptation when applied to those who have TBIs.
"There may also be sleep problems that are unique to patients with mTBI," he said, "for which there are no currently effective treatments."
Archives of Physical Medicine and Rehabilitation
NPR "All Things Considered"
University of Maryland Medical Center