It's not clear whether lifestyle before and after a
head injury is to blame for the increased risk, if the injury itself
has lingering effects, or both, researchers say.
"There is evidence in the study that points to lifestyle factors and
health before and after the head injury," said lead author Tom
McMillan, of the Institute of Health and Wellbeing at the University
High rates of death in the year following a severe head injury have
been well documented, McMillan and his colleagues write in the
Journal of Neurology, Neurosurgery and Psychiatry. But little is
known about risk of death after mild head injuries and especially
over the long term.
"When we started there was very little research published on late
outcome after head injury," McMillan told Reuters Health in an
His team did a study on disability after mild head injury and
noticed a high rate of deaths, which inspired them to look into it
further, he said.
Head injuries are extremely common, McMillan and his colleagues
write, and 95 percent of such injuries in Europe are considered
To see how people with mild head injuries fare over the years, the
researchers studied medical records for 2,428 adults admitted to
hospitals in Glasgow with mild head trauma between February 1995 and
They also identified two comparison groups whose members were
similar in age and background, but one group was made up of patients
hospitalized for something other than a head injury. The other group
contained community members who were not hospitalized and had no
history of head injury.
The researchers followed all the subjects for 15 years to compare
their rates of death and injury.
Overall, they found the group of head injury patients died at a rate
of 2.45 percent per year, compared to the community group's rate of
1.34 percent per year. The group with non-head injuries had a
mortality rate of 1.96 percent a year.
differences were more extreme among the younger subjects, with head
injury patients who were under 55 at the beginning of the study at
four times greater risk of dying than their peers in the community
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For the under-55 subjects, the death rate was 1.29 percent per
year in the head injury group compared to 0.75 percent per year in
the hospitalized group and 0.31 percent per year in the community
The authors found that the adult head injury patients tended to have
less healthy lifestyles both before and after they were hospitalized
and many were likely to have a history of other head injuries before
and after the beginning of the study period.
McMillan said some of the lifestyle factors seen in the head injury
group include habitual heavy drinking and inadequate exercise.
"We also know that having a head injury is itself a risk factor for
having a further head injury, and in those in the study who have a
repeat head injury, there is a greater risk of premature death," he
In addition to lifestyle factors, McMillan said there might be
chronic brain changes resulting from repeat head injury, but
cautioned that his study had no data on that question.
McMillan said that people are likely to recover quickly from
symptoms that occur soon after a single mild head injury.
"However they need to be aware of potential long-term risks that are
associated with lifestyle and also that they are at a greater risk
of repeat head injury, which can result in cumulative effects and
persisting symptoms," he said.
Journal of Neurology, Neurosurgery and
Psychiatry, online March 12, 2014.
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