Influence of Alcohol on Mortality in Traumatic Brain Injury

Traumatic brain injury (TBI) represents a major public health problem. Each year, 1.4 million people sustain TBI in the United States. 235,000 patients are hospitalized and 50,000 die. The leading cause of TBI in the general population is falls, where rates are highest among children ages 0 to 4 and among adults ages 75 or older. Falls are followed closely by motor vehicle crashes and assaults as overall causes of TBI. However, motor vehicle crashes result in the greatest number of TBI-related deaths and hospitalizations 1. TBI injuries are extremely costly from a public health perspective since they require expenditures for hospital care, extended care, and other medical services, as well as the loss of productivity that may follow the permanent neurological consequences of TBI. For example, the Centers for Disease Control and Prevention estimated that at least 5.3 million patients have a long-term or lifelong need for help with activities of daily living because of TBI 2. As early as 1985, the annual economic burden of TBI in the United States was estimated at $37.8 billion 3, and over the past several years it has increased to almost $60 billion annually 4. One source estimated the cost of acute care and rehabilitation for new cases of TBI at $9 to $10 billion annually in 1999 5. In addition, the psychosocial burden borne by families of individuals with TBI must be taken in account even though it cannot be financially evaluated. Although not all of these figures are from the current decade, it is clear that TBI represents a prevalent and costly public health issue. Alcohol contributes substantially to the morbidity and mortality of trauma patients, regardless of the type of injury suffered 6-9. Serum alcohol levels correlate closely with the extent of injury 10-12. In 2006, alcohol intoxication was involved in 32% of fatal motor-vehicle crashes in the United States 13. Approximately half of the alcohol-related deaths in trauma occur in pre-hospital settings 9, 14. Specifically in TBI, 35-81% of the injured patients are alcohol-intoxicated 15-16 and 42% of the TBI patients were heavy drinkers before injury 16. A study from the National Trauma Databank found similar rates 17. In contrast to the strong correlation between alcohol and pre-hospital mortality in TBI victims, the effects of alcohol on the outcome of injured patients surviving the field and admitted to the hospital is less clear. Indeed, some clinical studies surprisingly seem to suggest a beneficial effect of alcohol in injured patients with TBI. This review will analyze basic research in animal models and available clinical information to provide a realistic perspective regarding the effect of alcohol on the outcome of patients admitted to the hospital with a diagnosis of TBI. The investigational literature can be categorized into studies of the effects of low- moderate doses of alcohol in TBI animal models, investigations into the effects of high doses of alcohol in such models, and experiments directed at elucidating the mechanisms of such effects. We will consider each in turn before moving to the clinical literature.