Systematic review of the risk of dementia and chronic cognitive impairment after mild traumatic brain injury: results of the International Collaboration on Mild Traumatic Brain Injury Prognosis.

OBJECTIVE: To synthesize the best available evidence regarding the risk of dementia and chronic cognitive impairment (CCI) after mild traumatic brain injury (MTBI).

DATA SOURCES: MEDLINE and other databases were searched (2001-2012) using a previously published search strategy and predefined criteria. Peer-reviewed reports in 6 languages were considered.

STUDY SELECTION: Systematic reviews, meta-analyses, randomized controlled trials, cohort studies, and case-control studies, with a minimum of 30 MTBI cases in subjects of any age, assessing the risk of dementia or CCI after MTBI were selected.

DATA EXTRACTION: Eligible studies were critically appraised using a modification of the Scottish Intercollegiate Guidelines Network criteria. Two reviewers independently reviewed each study and extracted data from accepted articles (ie, with a low risk of bias) into evidence tables.

DATA SYNTHESIS: Evidence from accepted studies was synthesized qualitatively according to modified Scottish Intercollegiate Guidelines Network criteria, and prognostic information was prioritized as exploratory or confirmatory according to design. Of 77,914 records screened, 299 articles were eligible and reviewed. Methodological quality was acceptable for 101 (34%) articles, of which 1 article considered dementia and 7 articles considered CCI. The study examining the risk of dementia after MTBI did not find an association. One randomized controlled trial found that being informed about possible cognitive dysfunction after MTBI was associated with worse cognitive performance on standard tests. Children with MTBI and intracranial pathology ("complicated" MTBI) performed worse than did children without intracranial pathology. Children showed higher rates of cognitive symptoms a year after MTBI than did a control group.

CONCLUSIONS: There is a lack of evidence of an increased risk of dementia after MTBI. In children, objective evidence of CCI exists only for complicated MTBI. More definitive studies are needed to inform clinical decisions, assessment of prognosis, and public health policy.