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Updated: May 13, 2026
Detecting Behavioral Deficits in Rats After Traumatic Brain Injury
Published on: January 30, 2018
Age Suppresses the Association Between Traumatic Brain Injury Severity and Functional Outcomes: A Study Using the
Laraine Winter1, Helene Moriarty, Keith M Robinson
1Author Affiliations: M. Louise Fitzpatrick College of Nursing (Drs Winter and Whitehouse), Villanova University, Villanova, Pennsylvania; Research Service (Dr Winter, Dr Moriarty, and Ms Schmidt), Nursing Service (Dr Moriarty), Physical Medicine and Rehabilitation/Rehabilitation Medicine Service (Dr Robinson and Dr Swanson), Center for Neurotrauma, Neurodegeneration and Restoration (Dr Swanson), Corporal Michael J. Crescenz Veterans Affairs Medical Center, Department of Physical Medicine and Rehabilitation (Dr Robinson and Dr Swanson), Perelman School of Medicine, University of Pennsylvania, and Division of Biostatistics, Department of Pharmacology, Physiology, and Cancer Biology (Dr Leiby), Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania.
Objectives:
Recovery from traumatic brain injury (TBI) is extremely difficult to predict, with TBI severity usually demonstrating weak predictive validity for functional or other outcomes. A possible explanation may lie in the statistical phenomenon called suppression, according to which a third variable masks the true association between predictor and outcome, making it appear weaker than it actually is. Age at injury is a strong candidate as a suppressor because of its well-established main and moderating effects on TBI outcomes. We tested age at injury as a possible suppressor in the predictive chain of effects between TBI severity and functional disability, up to 10 years post-TBI.
Setting:
Follow-up interviews were conducted during telephone interviews.
Participants:
We used data from the 2020 NDILRR Model Systems National Dataset for 4 successive follow-up interviews: year 1 ( n = 10,734), year 2 ( n = 9174), year 5 ( n = 6,201), and year 10 ( n = 3027).
Design:
Successive cross-sectional multiple regression analyses.
Main Measures:
Injury severity was operationalized using a categorical variable representing duration of posttrauma amnesia. The Glasgow Outcomes Scale-Extended (GOS-E) operationally defined functioning. Sociodemographic characteristics having significant bivariate correlations with GOS-E were included.
Results:
Entry of age at injury into the regression models significantly increases the association between TBI severity and functioning up to 10 years post-TBI.
Conclusions:
Age at injury is a suppressor variable, masking the true effect of injury severity on functional outcomes. Identifying the mediators of this suppression effect is an important direction for TBI rehabilitation research.
