Living: the ultimate team sport

 By Ramon Diaz-Arrastia, MD, PhD

Traumatic brain injury (TBI) has been one of the most common maladies in human history.¹  Recent quantitative studies from burial sites of prehistoric modern humans^2;3 indicate that approximately one-third of our ancestors experienced cranial trauma sufficient to result in a skull fracture.   This high rate of TBI in prehistoric humans makes it likely that genetic variants that confer resistance to brain trauma, or foster repair and plasticity of injured neural tissue, would have been selectively favored through evolution.  TBI remains a major problem in modern societies, primarily as a consequence of traffic accidents and falls.   In the United States alone, an estimated 1.7 million people sustain a TBI annually, of which 275,000 require hospitalization and 52,000 die.⁴  Rates are even higher in developing countries.⁵

TBI is perhaps the best established environmental risk factor for dementia.  Cross-sectional and longitudinal studies…