Premorbid Intellectual Functioning, Education, and Brain Size in Traumatic Brain Injury: An Investigation of the Cognitive Reserve Hypothesis

Abstract

Cognitive reserve theories have been postulated in an attempt to explain individual differences in functional outcome following cerebral insult or disease. These theories suggest that higher education and psychometric intelligence may preserve functional capacity regardless of injury or disease severity. This study investigated cognitive reserve in 25 participants with traumatic brain injury (TBI) using high-resolution magnetic resonance imaging (MRI) analyses. We examined the relationships between total intracranial volume (TICV), ventricle-tobrain ratio (VBR), education level, and standardized testing obtained prior to injury with post-injury cognitive outcome. Participants with lower post-injury IQ scores had significantly lower TICV values, irrespective of injury severity, and experienced significantly greater change in IQ from pre- to post-injury. TICV and education correctly predicted participants' post-injury IQ category ( Y 90 or < 90). However, premorbid standardized testing (PST) scores did not predict cognitive outcome. The results of this study suggest that larger premorbid brain volume and higher education level may decrease vulnerability to cognitive deficits following TBI, consistent with the notion of a cognitive reserve.

The Effect of Premorbid Demographic Factors on the Recovery of Neurocognitive Function in Traumatic Brain Injury Patients

“…We analyzed these outcomes with intelligence and memory divided them into subtypes. Cognitive intelligence and memory reserves are consistent with the prevailing clinical assumption that greater premorbid intellectual functioning is related to better outcome following TBI 11) . This theory suggests that higher education level and intelligence may preserve functional capacity regardless of injury or disease severity 11) .…”

“…Cognitive intelligence and memory reserves are consistent with the prevailing clinical assumption that greater premorbid intellectual functioning is related to better outcome following TBI 11) . This theory suggests that higher education level and intelligence may preserve functional capacity regardless of injury or disease severity 11) . Some studies have demonstrated that individuals with fewer years of education may be more vulnerable to the functional impact of TBI on intelligence quotient (IQ) outcome, regardless of the injury severity or degree of structural brain damage 11,13) .…”

“…This theory suggests that higher education level and intelligence may preserve functional capacity regardless of injury or disease severity 11) . Some studies have demonstrated that individuals with fewer years of education may be more vulnerable to the functional impact of TBI on intelligence quotient (IQ) outcome, regardless of the injury severity or degree of structural brain damage 11,13) .…”

Cognitive reserve and executive function: Effect on judgment of health and safety

“…This pattern has been observed across a wide range of brain pathologies, including moderate to severe traumatic brain injury [9], cerebrovascular disease [10], hepatitis C [11], and AD [12]. Overall, a strong body of research has found support that intellectual ability, education, and occupational attainment are associated with cognitive reserve [7,[11][12][13][14][15][16][17].…”

Traumatic Brain Injury and Executive Functioning in an Incarcerated Sample

“…These deficits can be short-or longterm and are thought to be influenced by several factors, including age at injury, premorbid IQ, and the level of education attained by the individual ). Satz (1993 proposed a theory of cognitive reserve as a possible explanation for this heterogeneity of cognitive changes seen following TBI, and subsequent research has shown support for the theory (Ropacki & Elias, 2003;Kesler, Adams, Blasey, & Bigler, 2003).…”