The Role of Cognitive Reserve in Recovery From Traumatic Brain Injury.
Kayla A Steward, Richard Kennedy, Thomas A Novack and 3 others
PMID 28520675WHAT IT FOUND
Estimated premorbid IQ did not predict faster recovery after traumatic brain injury.
The advantage was not specific to injury severity. It was linked to better initial cognitive performance.
Key findings
01Only TBI severity, not estimated IQ, significantly moderated rate of change for the cognitive domains.
02The effect of estimated IQ on initial impairment did not depend on injury severity.
03A 10-point increase in estimated premorbid IQ was linked to a 0.31 standard deviation increase in processing speed/executive function, a 0.37 increase in memory, and a 0.25 increase in verbal fluency.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The first cognitive assessment was one month after injury, so people with milder injury may already have recovered before measurement. Only three visits were available, so the analysis forced recovery to look linear even though recovery may level off. Twenty-five TBI participants and 17 controls did not complete all visits. The sample was relatively small, so modest effects on recovery speed could have been missed. Premorbid IQ was estimated from word reading, not measured before injury, and may underestimate IQ in moderate-to-severe TBI. Moderate TBI cases were grouped with severe TBI cases because there were too few.
Declared interests
The study was part of a larger NIH-funded longitudinal study. The authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that people with higher estimated premorbid IQ recover faster after traumatic brain injury. The study found no effect of IQ on recovery speed, and the IQ advantage was not stronger in people with more severe injury.