People who suffer traumatic brain injuries face an elevated risk of death from suicide or accidents for years to come, according to a new study based on four decades of data on hundreds of thousand of patients in Sweden.
Those who survived the immediate aftermath of moderate and severe traumatic brain injuries were three times more likely than people without such injuries to die prematurely, defined by the researchers as before age 56.
Experts said the study was likely to spur calls for long-term monitoring of some brain injury patients. By virtue of its size and scope, the analysis, published Wednesday in JAMA Psychiatry, puts an authoritative stamp on a growing body of evidence that impacts to the brain can be deadly in ways that are not easily apparent.
“I don’t think you can get much more valuable or detailed data,” said Dr. Michael Yochelson, a brain trauma expert at MedStar National Rehabilitation Hospital in Washington who was not involved in the study.
The team of British and Swedish researchers focused on brain injuries involving skull fractures, internal bleeding or loss of consciousness for more than an hour. But the data also suggested a similar association with concussions, also known as mild traumatic brain injuries, which are far more common and a source of growing concern in the military and contact sports.
Though scientists have suspected that brain trauma is associated with an increased risk of early death, proving it requires long-term data in a large population.
Dr. Seena Fazel, a psychiatrist at the University of Oxford and lead author of the study, found exactly that in Sweden, a country of 9.5 million that has tracked births, deaths and healthcare of all its citizens for decades.
The analysis studied all 218,300 Swedes born after 1953 who were diagnosed with traumatic brain injuries other than concussions from 1969 to 2009 and survived at least six months after their injuries.
A total of 2,378 — or 1.1% — died before age 56. That was three times the rate in a control group of 2.2 million people without such injuries. The comparison took into account age, sex, income and other demographic factors.
In the brain injury group, 574 deaths resulted from various kinds of accidents, and 522 were suicides. Their fatal accident rate was more than quadruple that of the control group, and their suicide rate was more than triple.
Death rates remained elevated even five years after the brain injuries occurred. Experts said that brain injury patients tended to be risk takers in the first place, which may help explain their elevated death rates.
The Swedish data also show that even before their brain injuries, the subjects were more likely to have a psychiatric disorder or a substance abuse problem. Those factors not only boosted their odds of suffering a traumatic brain injury in the first place, but also increased their risk for suicide and fatal accidents.
But the data strongly suggested that the injury itself played an important role in mortality. Among people with psychiatric disorders or substance abuse problems, those with traumatic brain injuries had much higher rates of premature death.
Moreover, the researchers compared 150,513 of the brain injury patients with their siblings without brain injuries. Even though siblings share a large portion of their DNA and many of the same childhood experiences — factors that shape personality and strongly influence mortality — the brain injury patients were 2.5 times more likely to die early.
Donald Stein, a traumatic brain injury researcher at Emory University in Atlanta, said the results suggested that the brain injury itself increased the risk of mortality. Many of the injuries occur in parts of the brain responsible for judgment, executive function and impulse control.
“If these people are higher risk takers and have frontal temporal cortex injuries that exacerbate the problems, it’s not surprising that they have higher rates of suicide,” Stein said.
Current clinical guidelines for treating traumatic brain injuries focus on short-term survival.
In an editorial accompanying the study, Dr. Robert Robinson, a psychiatrist at the University of Iowa, wrote that one cost-effective approach would be screening brain injury patients for personality traits, psychiatric disorders or substance abuse problems that would place them at the greatest risk, then treating them with anti-depressants or other therapies.
The study did not devote the same attention to concussions, the signature injury from roadside bombs used against U.S. troops in recent wars and a routine occurrence in football and other contact sports.
The researchers conducted a separate analysis of 333,118 people who were diagnosed with concussions and found that they were twice as likely as a control group to die early. But that part of the study did not control for psychiatric disorders or include a comparison to siblings.
In addition, the data are incomplete, since many concussions are never diagnosed.