Traumatic brain injuries are likely more common than previously thought

"Even mild traumatic brain injuries can affect sensory-motor functions, thinking and awareness, and communication," says study author Allen Brown, M.D., director of brain rehabilitation research at Mayo Clinic. "In assessing frequency, we have likely been missing a lot of cases. This is the first population-based analysis to determine prevalence along the whole spectrum of these injuries."

Researchers used the Mayo Traumatic Brain Injury Classification System, a new brain injury method that classifies head injuries along a more comprehensive scale than ever before. The categories label patients with "definite," "probable" and "possible" TBIs, providing a way to incorporate symptoms such as a brief period of unconsciousness or even an injured patient's complaint of dizziness or nausea.

Using the Rochester Epidemiology Project, a several decades-long compilation of medical records in Olmsted County, Minn., the team determined that TBIs occur in as many as 558 per 100,000 people, compared to the 341 per 100,000 estimated by the CDC. Researchers found that 60 percent of injuries fell outside the standard categorization used by the CDC, even though two-thirds of them were symptomatic. Mayo researchers found the elderly and the young were found most at risk for "definite" and "possible" injury, respectively, and men were more at risk than women. The findings reinforce ongoing efforts by the CDC to create a brain injury classification that more broadly encompasses traumatic head injury.

"With more complete assessment of frequency, we'll have better tools to develop prevention programs, optimize treatments, understand cost-effectiveness of care and predict outcomes for patients," says Dr. Brown.

Other study authors include Cynthia Leibson, Ph.D.; Jeanine Ransom; Nancy Diehl; Patricia Perkins; and Jay Mandrekar, Ph.D., all of Mayo Clinic, and James Malec, Ph.D., of the Rehabilitation Hospital of Indiana.