A Meta-Analysis of Working Memory Impairments in Survivors of Moderate-to-Severe Traumatic Brain Injury

Objectives: To establish the magnitude of deficits in working memory (WM) and short-term memory (STM) in those with moderate-to-severe traumatic brain injury (TBI) relative to age-matched, healthy controls and to explore the moderating effects of time since injury and age at injury on these impairments. Method: Twenty-one studies that compared the WM and/or STM abilities of individuals with at least a moderate TBI relative to healthy controls were included in a random effects meta-analysis. Measures used to examine memory performance were categorized by modality (visuospatial, verbal) and memory system (WM, STM). Results: Individuals with TBI had significant deficits in verbal STM (Cohen's d =.41), visuospatial WM (Cohen's d =.69), and verbal WM (Cohen's d =.37) relative to controls. Greater decrements in verbal STM and verbal WM skills were associated with longer time postinjury. Larger deficits were observed in verbal WM abilities in individuals with older age at injury. Conclusion: Evidence for WM impairments following TBI is consistent with previous research. Larger verbal STM and verbal WM deficits were related to a longer time postinjury, suggesting that these aspects of memory do not "recover" over time and instead, individuals might show increased rates of cognitive decline. Age at injury was associated with the severity of verbal WM impairments, with larger deficits evident for injuries that occurred later in life. Further research needs to chart the long-term effects of TBI on WM and to compare the effects of injury on verbal relative to visuospatial memory.