Post-traumatic amnesia predicts intelligence impairment following traumatic brain injury: a meta-analysis
- Correspondence to M Königs, VU University Amsterdam, FPP Department of Clinical Neuropsychology, Van der Boechorststraat 1, Amsterdam 1081 BT, The Netherlands;
Contributors MK made a substantial contribution to conception and design, acquisition of the data, analysis and interpretation of the data, drafting the manuscript and gave final approval of the version to be submitted. JFdK made a substantial contribution to conception and design, analysis and interpretation of the data, drafting the manuscript and gave final approval of the version to be submitted. JO made a substantial contribution to conceptions and design, interpretation of the data, drafting the manuscript and gave final approval of the version to be submitted.
- Received 1 March 2012
- Revised 15 May 2012
- Accepted 13 June 2012
- Published Online First 11 July 2012
Context Worldwide, millions of patients with traumatic brain injury (TBI) suffer from persistent and disabling intelligence impairment. Post-traumatic amnesia (PTA) duration is a promising predictor of intelligence following TBI.
Objectives To determine (1) the impact of TBI on intelligence throughout the lifespan and (2) the predictive value of PTA duration for intelligence impairment, using meta-analytic methods.
Methods Electronic databases were searched for peer reviewed articles, published until February 2012. Studies reporting intelligence following TBI and injury severity by PTA duration were included. Meta-analytic methods generated effect sizes for full scale IQ (FSIQ), performance IQ (PIQ) and verbal IQ (VIQ), following mild TBI (PTA duration 1–24 h) and severe TBI (PTA duration >7 days), during the subacute phase of recovery (≤6 months post-injury) and the chronic phase (>6 months post-injury). Meta-regression elucidated the predictive value of PTA duration for intelligence impairment.
Results Patients with severe TBI exhibited large depressions in FSIQ in the subacute phase of recovery (d=−1.07, 95% CI to 1.52 to −0.62; p<0.001), persisting into the chronic phase (d=−0.78, 95% CI −1.06 to −0.51; p<0.001). PIQ was more severely affected than VIQ in the subacute phase (Q(1) =3.85; p<0.05) but not in the chronic phase (Q(1) =0.03, p=0.87). Most importantly, longer PTA duration strongly predicted greater depressions of FSIQ and PIQ in the subacute phase (−0.76 ≤ βs ≤ −0.73, Ps<0.01) and FSIQ, PIQ and VIQ in the chronic phase (−0.80 ≤ βs ≤ −0.61, Ps<0.05).
Conclusions PTA duration is a valuable predictor of intelligence impairment following TBI. Results support the routine assessment of PTA duration in clinical settings.
Funding This work was supported by the Netherlands Organisation for Scientific Research (NWO) grant No 022.003.010. The funder had no role in the conductance of this study other than providing financial support.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.