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Frequency of Mild Traumatic Brain Injury in Iraq and Afghanistan: Are We Measuring Incidence or Prevalence?

Rona, Roberto J. FFPH; Jones, Margaret BA; Fear, Nicola T. DPhil OXON; Sundin, Josefin PhD; Hull, Lisa MSc; Wessely, Simon FMedSci

Section Editor(s): Caplan, Bruce PhD, ABPP; Bogner, Jennifer PhD, ABPP

The Journal of Head Trauma Rehabilitation: January/February 2012 - Volume 27 - Issue 1 - p 75–82
doi: 10.1097/HTR.0b013e31823029f6
TBI in the Military

Objective: Rates of mild traumatic brain injury (mTBI) differ considerably between US and UK forces, despite similar methodology and similar exposure risks. We assessed, in the UK forces, if the differences in rates based on last deployment can be explained by differences in deployment length, given that US forces deploy for approximately twice as long as UK forces.

Participants: A total of 3763 personnel deployed to Iraq or Afghanistan who completed a questionnaire between 2007 and 2009.

Main Outcome Measures: Mild traumatic brain injury in the last deployment contrasted to current posttraumatic stress disorder, psychological distress (General Health Questionnaire-12), multiple physical symptoms, and alcohol misuse.

Results: In the Army and Royal Marines, there was an association between length of deployment (per month) and mTBI (odds ratio: 1.31, 95% confidence interval: 1.13–1.51), which remained significant after adjustment for confounders (odds ratio: 1.25, 95% confidence interval: 1.08–1.45). No other outcome was associated with length of deployment. Results based on the total sample were similar to those in the Royal Marine and Army sample, except for adjusted multiple physical symptoms.

Conclusions: Comparisons of mTBI rates should take account of length of deployment when based on last deployment. Doing so reduces but does not eliminate the differences between UK and US forces.

King's Centre for Military Health Research (Drs Rona and Wessely, Mss Jones and Hull) and Academic Centre for Defence Mental Health (Drs Fear and Sundin), Weston Education Centre, King's College of London, England.

Corresponding Author: Roberto J. Rona, FFPH, King's Centre for Military Health Research, Weston Education Centre, King's College London, 10 Cutcombe Rd, London SE5 9RJ, England (

The authors are grateful to Ministry of Defence for their help in the execution of this study, in particular we thank the Surgeon General's Department, the Defence Analytical Services and Advice, the single services, the Joint Personnel Administration, and the Veterans Policy Unit.

The UK Ministry of Defence funded this project.

Simon Wessely is Honorary Civilian Consultant Advisor to the British Army. The other authors declare they have no conflicts of interest.

© 2012 Lippincott Williams & Wilkins, Inc.