People who sustain a concussion or a more severe traumatic brain injury are likely to have sleep problems that continue for at least a year and a half.
A study of 31 patients with this sort of brain injury found that 18 months afterward, they were still getting, on average, an hour more sleep each night than similar healthy people were getting. And despite the extra sleep, 67 percent showed signs of excessive daytime sleepiness. Only 19 percent of healthy people had that problem.
Surprisingly, most of these concussed patients had no idea that their sleep patterns had changed.
"If you ask them, they say they are fine," says Dr. Lukas Imbach, the study's first author and a senior physician at the University Hospital Zurich in Zurich. When Imbach confronts patients with their test results, "they are surprised," he says.
The results, published Thursday in the online edition of the journal Neurology, suggest there could be a quiet epidemic of sleep disorders among people with traumatic brain injuries. The injuries are diagnosed in more than 2 million people a year in the United States. Common causes include falls, motor vehicle incidents and assaults.
Previous studies have found that about half of all people who sustain sudden trauma to the brain experience sleep problems. But it has been unclear how long those problems persist. "Nobody actually had looked into that in detail," Imbach says. A sleep disorder detected 18 months after an injury will linger for at least two years, and probably much longer, the researchers say.
The results suggest that doctors who treat traumatic brain injuries can't rely on their patients alone to report sleep problems, says Dr. Brian Edlow, a neurologist at Massachusetts General Hospital, who wrote an editorial accompanying the study. "There may be other tools that we need to detect sleep-wake disturbances in this patient population," he says.
One possibility is referring patients with concussions and other brain injuries for sleep studies. That's a costly option, Edlow says. But so is leaving a sleep disturbance undetected.
"Excessive daytime sleepiness can decrease people's productivity at work or at school," he says. In some cases, he says, it can even make it unsafe to drive.
It's not clear what's causing sleepiness so long after a brain injury. Doctors think that getting extra sleep soon after an injury helps the brain heal. But if sleepiness persists, it becomes a problem, Edlow says.
It's also surprising that sleepiness lingered longer-term, even in patients who had relatively mild injuries, Edlow says.
In severe injuries, the forces are so great that they actually tear apart circuits deep inside the brain. "It's the disruption of these circuits that is believed to cause sleep-wake disturbances," Edlow says.
But these circuits don't appear to be damaged in mild concussions, he says. "So there may be some other mechanism at work."
The challenge now, Edlow says, is to figure out what that mechanism is.
AUDIE CORNISH, HOST:
People who suffer from concussions or traumatic brain injuries often feel sleepy even when they get a good night's rest. New research shows that feeling can last for more than a year. It suggests a silent epidemic of sleep disorders among those with brain injuries, as NPR's Jon Hamilton reports.
JON HAMILTON, BYLINE: Traumatic brain injuries, or TBIs, affect more than 2 million people a year in the U.S. alone, and studies show that about half of these people experience some sort of sleep disturbance while they're recovering. Lukas Imbach and a team of researchers of the University Hospital Zurich in Switzerland wanted to know how long these sleep problems last.
LUKAS IMBACH: We guessed that they would persist quite for a long time, but nobody actually had looked into that in detail.
HAMILTON: So the team studied the sleep patterns of 31 patients 18 months after they'd sustained a traumatic brain injury. Then the scientists compared the sleep patterns of the TBI patients with those of 42 healthy people.
IMBACH: The main finding was that those patient just had higher sleep need. They slept longer hours. So on average, they slept one hour more than healthy controls.
HAMILTON: About eight hours instead of seven, but Imbach says that didn't mean the TBI patients were well-rested.
IMBACH: You might think that if you sleep more, then at least you're not sleepy anymore. But those patients are still sleepy during the day.
HAMILTON: Tests showed that two-thirds of the TBI patients had excessive daytime sleepiness. Imbach says the results, if they are replicated in larger groups, could mean that traumatic brain injuries are responsible for long-term sleep problems in millions of people. Imbach says this is especially troubling because his study found that most TBI patients were unaware that the injury had changed their sleep patterns.
IMBACH: Even if you confront them with our findings, the patients themselves - they're really surprised.
HAMILTON: And so are some doctors who treat patients with traumatic brain injuries.
BRIAN EDLOW: I typically rely upon patients' reports of their symptoms.
HAMILTON: Brian Edlow is a neurologist at Massachusetts General Hospital
EDLOW: After reading this study, the question now arises - is it sufficient to only rely upon patients' reporting of symptoms of daytime sleepiness or disturbed sleep-wake cycles? Is there maybe other tools that we need to detect sleep-wake disturbances in this patient population?
HAMILTON: Edlow, who wrote an editorial accompanying the studies, says some TBI patients may need to be evaluated in a sleep lab even if they say they are fine.
EDLOW: Excessive daytime sleepiness can decrease people's productivity at work or at school. It's one of the most common complaints that people have, and it's one of the most frustrating symptoms because it's so difficult to treat.
HAMILTON: Daytime sleepiness can also make it unsafe to do things like drive a car. What is making the TBI patients in this study sleepy is a mystery. Edlow says in severe injuries, the forces are so great that they actually tear apart circuits deep inside the brain.
EDLOW: And it's the disruption of these circuits that is believed to cause sleep-wake disturbances in patients who have had a traumatic brain injury.
HAMILTON: Extra sleep may help the brain repair the damage, but the long-term sleep disturbances in this study aren't helping that process. And Edlow says the study found sleep problems occurred even when the injuries were relatively minor.
EDLOW: And so there may be some other mechanism at work that is causing sleep-wake disturbances in these patients with milder forms of injury.
HAMILTON: Edlow says the challenge now is to figure out what that mechanism is. The new study appears in the journal Neurology. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.