Who Gets Head Trauma or Recruited in Mild Traumatic Brain Injury Research?

Mild traumatic brain injury (mTBI) is a public health problem. Outcome from mTBI is heterogeneous in part due to pre-injury individual differences that typically are not well described or understood. Pre-injury health characteristics of all consecutive patients (n=3023) who underwent head computed tomography due to acute head trauma in the emergency department of Tampere University Hospital, Finland, between August 2010 and July 2012 were examined. Patients were screened to obtain a sample of working age adults with no pre-injury medical or mental health problems who had sustained a "pure" mTBI. Of all patients screened, 1990 (65.8%) fulfilled the mTBI criteria, 257 (8.5%) had a more severe TBI, and 776 (25.7%) had a head trauma without obvious signs of brain injury. Injury-related data and participant-related data (e.g., age, sex, diagnosed diseases, and medications) were collected from hospital records. The most common pre-injury diseases were circulatory (39.4%-43.2%), neurological (23.7%-25.2%), and psychiatric (25.8%-27.5%) disorders. Alcohol abuse was present in 18.4%-26.8%. The most common medications were for cardiovascular (33.1%-36.6%), central nervous system (21.4%-30.8%), and blood clotting and anemia indications (21.5%-22.6%). Of the screened patients, only 2.5% met all the enrollment criteria. Age, neurological conditions, and psychiatric problems were the most common reasons for exclusion. Most of the patients sustaining an mTBI have some pre-injury diseases or conditions that could affect clinical outcome. By excluding patients with pre-existing conditions, the patients with known risk factors for poor outcome remain poorly studied.