Traumatic brain injury is more widespread than previously estimated

BMJ 2012; 345 doi: (Published 27 November 2012) Cite this as: BMJ 2012;345:e8098
  1. Bob Roehr
  1. 1Washington, DC

An estimated 54-60 million people worldwide sustain a traumatic brain injury every year, a new study indicates, about six times the previous estimate.1 Between 2.2 million and 3.6 million of the injuries are moderate to severe.

Traumatic brain injury is the leading cause of long term disability among children and young adults and cost an estimated $406bn (£250bn; €315bn) in the United States in 2000. It is projected to become the third largest cause of disease burden worldwide by 2020.

Earlier projections focused on acute injury where medical attention was sought. But research has generated a growing body of evidence that mild injury, particularly a series of insults to the brain without time for proper recovery, can have a significant long term clinical effect, with symptoms that can be similar to those of Alzheimer’s disease, Parkinson’s disease, and dementia.

The Brain Injury Outcomes New Zealand in the Community (BIONIC) study looked at 172 000 people in urban and rural parts of one area in New Zealand during 2010-11.1 It engaged with all levels of healthcare staff, schools, residential facilities, sports groups, and the general public to gather as complete a record as possible of potential brain trauma.

It identified 1369 cases of traumatic brain injury, 95% of which were mild. The overall incidence was 790 cases per 100 000 people a year. This was significantly higher than the World Health Organization estimate of 100-300 cases per 100 000 people a year.

Most (69%) injuries occurred in men under the age of 35 years. Moderate to severe injury was most likely to occur in those older than 15 years (90%), while mild injury was most prevalent in people between the ages of 15 and 34 years (40%). A substantial portion (36%) of injured people did not present at a hospital at the acute stage of injury.

Falls were the most common cause of traumatic brain injury before the age of 5 years and in the later decades of life. Traffic crashes and assaults peaked as causes in late adolescence and early adulthood.

“We believe that our results are comparable with those from other high-income settings,” the authors wrote. They extrapolated the findings to a worldwide context and argued that “they are still likely to be conservative because TBI [traumatic brain injury] incidence in low-income to middle-income countries is thought to be far greater than it is in high-income countries.”

Mild traumatic brain injury had been underestimated and overlooked because it seldom resulted in immediate presentation to healthcare providers, the authors said. But as understanding of its long term effects had grown, and as life expectancy continued to expand, it would be a growing problem, they added.


Cite this as: BMJ 2012;345:e8098