Background: The most widely used methods of describing traumatic brain injury 
(TBI) are the Glasgow Coma Scale (GCS) and the Abbreviated Injury Scale (AIS). 
Recent evidence suggests that presenting GCS in older patients may be higher 
than that in younger patients for an equivalent anatomical severity of TBI. This 
study aimed to assess these observations with a propensity-score matching 
approach using the data from Trauma Registry System in a Level I trauma center. 
Methods: We included all adult patients (aged ≥20 years old) with moderate to 
severe TBI from 1 January 2009 to 31 December 2016. Patients were categorized 
into elderly (aged ≥65 years) and young adults (aged 20-64 years). The severity 
of TBI was defined by an AIS score in the head (AIS 3‒4 and 5 indicate moderate 
and severe TBI, respectively). We examined the differences in the GCS scores by 
age at each head AIS score. Unpaired Student's t- and Mann-Whitney U-tests were 
used to analyze normally and non-normally distributed continuous data, 
respectively. Categorical data were compared using either the Pearson chi-square 
or two-sided Fisher's exact tests. Matched patient populations were allocated in 
a 1:1 ratio according to the propensity scores calculated using NCSS software 
with the following covariates: sex, pre-existing chronic obstructive pulmonary 
disease, systolic blood pressure, hemoglobin, sodium, glucose, and alcohol 
level. Logistic regression was used to evaluate the effects of age on the GCS 
score in each head AIS stratum. Results: The study population included 2081 
adult patients with moderate to severe TBI. These patients were categorized into 
elderly (n = 847) and young adults (n = 1234): each was exclusively further 
divided into three groups of patients with head AIS of 3, 4, or 5. In the 162 
well-balanced pairs of TBI patients with head AIS of 3, the elderly demonstrated 
a significantly higher GCS score than the young adults (14.1 ± 2.2 vs. 13.1 ± 
3.3, respectively; p = 0.002). In the 362 well-balanced pairs of TBI patients 
with head AIS of 4, the elderly showed a significantly higher GCS score than the 
young adults (13.1 ± 3.3 vs. 12.2 ± 3.8, respectively; p = 0.002). In the 89 
well-balance pairs of TBI patients with head AIS of 5, no significant 
differences were observed for the GCS scores. Conclusions: This study 
demonstrated that elderly patients with moderate TBI present higher GCS score 
than younger patients. This study underscores the importance of determining of 
TBI severity in this group of elderly patients based on the GCS score alone. A 
lower threshold of GCS cutoff should be adopted in the management of the elderly 
patients with TBI.