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ORIGINAL ARTICLE COPYRIGHT © 2018 THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES INC.
Age, Gender and Mechanism of Injury
Interactions in Post-Concussion Syndrome
Brenda Varriano, George Tomlinson, Apameh Tarazi, Richard Wennberg,
Charles Tator, Maria Carmela Tartaglia
ABSTRACT: Background: Certain factors such as age and gender seem to affect the risk of developing post-concussion syndrome (PCS). We
assessed the interactions between age, gender, concussion history and mechanism of injury in PCS patients so that a better understanding could
guide the development of targeted prevention strategies. Methods: Demographic data including age, gender, concussion mechanism of injury and
concussion history were collected from (1) a prospective study evaluating PCS biomarkers and (2) a retrospective chart review of PCS patients. A
total of 437 PCS patients who were assessed at the Canadian Concussion Centre or Toronto Western Hospital, Toronto, ON, were included.
Results: Overall, there were more men with PCS; however, a greater percentage of women had PCS after a single concussion. The results showed
that age, gender and concussion history are conditionally dependent on the mechanism of injury, and independent of one another. The relative
frequency of having PCS was greater in the following instances: (1) being a woman and having had concussion from a fall or motor vehicle
collision (MVC), (2) being older and having had concussion from a fall or MVC or (3) having a single concussion with cause being MVC or fall.
Conclusion: In patients with PCS, age and gender interact with the mechanism of injury to influence the risk of concussion. Targeted prevention
strategies may be essential to prevent injuries leading to PCS.
RÉSUMÉ: Relations entre l’âge, le sexe et les mécanismes d’une lésion cérébrale dans le cas du syndrome post-commotionnel. Contexte:
Certains facteurs, par exemple l’âge et le sexe, semblent avoir une incidence sur le risque d’être atteint du syndrome post-commotionnel (SPC).
Afin de mieux comprendre cet ensemble de symptômes et d’orienter les efforts visant à développer des stratégies de prévention ciblées, nous avons
donc tenté d’évaluer, chez des patients atteints du SPC, les relations entre l’âge, le sexe, des antécédents de commotions cérébrales et les
mécanismes ayant causé une lésion cérébrale. Méthodes: Des données portant sur l’âge, le sexe, les mécanismes d’une lésion cérébrale et des
antécédents de commotion cérébrale ont été collectées à partir de deux sources: (1) une étude prospective évaluant les marqueurs du SPC; (2) un
examen rétrospectif des dossiers de patients atteints du SPC. Au total, 437 patients de ce type ayant été évalués au Canadian Concussion Centre ou
au Toronto Western Hospital (Ontario) ont été inclus dans cette étude. Résultats:Dansl’ensemble, on a recensé plus d’hommes atteints du SPC.
Cela dit, un pourcentage plus élevé de femmes ont présenté un tel syndrome à la suite d’une seule commotion cérébrale. Nos résultats ont également
montré que certains des facteurs mentionnés ci-dessus (l’âge, le sexe ainsi que des antécédents de commotion cérébrale) sont tributaires des
mécanismes d’une lésion cérébrale et indépendants les uns des autres. Ainsi, la fréquence relative de cas de SPC était plus élevée au regard des
situations suivantes: (1) être de sexe féminin et avoir subi une commotion cérébrale à la suite d’une chute ou d’un accident automobile; (2) être plus
âgé et avoir subi une commotion cérébrale à la suite d’une chute ou d’un accident automobile; (3) avoir subi une seule commotion cérébrale
pouvant être attribuée à un accident automobile ou à une chute. Conclusions: Couplés aux mécanismes d’une lésion cérébrale dans le cas de
patients atteints du SPC, tant l’âge que le sexe sont susceptibles d’avoir une incidence sur le risque de subir une commotion cérébrale. Il se pourrait
donc que des stratégies de prévention davantage ciblées soient essentielles afin de prévenir les lésions entraînant un SPC.
Keywords: Post-concussion syndrome, Gender, Age, Mechanism of Injury
doi:10.1017/cjn.2018.322 Can J Neurol Sci. 2018; 45: 636-642
Concussion, also known as mild traumatic brain injury
(mTBI), is becoming a growing concern. A concussion is a
complex process induced by a biomechanical force that affects the
brain.
1
Approximately 100-300/100,000 individuals are treated
for concussion at a hospital annually, which underestimates the
true incidence of concussion as many do not seek medical care.
2
From the Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, Canada (BV, MCT); Institute of Health Policy, Management and Evaluation,
University of Toronto, Toronto, Ontario, Canada (GT); Department of Medicine, University Health Network, Toronto, Ontario, Canada (GT); Department of Medicine, Mt. Sinai Hospital,
Toronto, Ontario, Canada (GT); Canadian Concussion Centre, TorontoWestern Hospital, Toronto, Ontario, Canada (AT, CT, MCT); Concussion Research Clinic, Toronto Western Hospital,
Toronto, Ontario, Canada (AT, RW, CT, MCT); Division of Neurosurgery, Krembil Neuroscience Centre, Toronto Western Hospital, Toronto, Ontario, Canada (CT); Department of Surgery,
University of Toronto, Toronto, Ontario, Canada (CT); Division of Neurology, Krembil Neuroscience Centre, Toronto Western Hospital, Toronto, Ontario, Canada (RW, MCT).
Correspondence to: Maria Carmela Tartaglia, Tanz Centre for Research in Neurodegene rative Diseases, University of Toronto, 399 Bathurst St. WW5-449 Toronto, ON, Canada M5T 2S8.
Email: carmela.tartaglia@uhn.ca
Presented at the Concussion in Women and Girls Symposium, Oral Presentation, Saturday, September 23, 2017, Toronto, ON, Canada.
RECEIVED JANUARY 16, 2018. FINAL REVISIONS SUBMITTED MAY 26, 2018. DATE OF ACCEPTANCE JUNE 24, 2108.
636
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Most people (85%-90%) recover from concussion within 7-10
days after the injury, but the symptoms can persist for months,
years or indefinitely leading to a condition referred to as post-
concussion syndrome (PCS).
3-6
Although there is debate over the
definition of PCS, the Diagnostic and Statistical Manual of Mental
Disorders (DSM-IV) is one of the more common criteria, along
with the International Statistical Classification of Diseases and
Related Health Problems (ICD-10), and includes the following:
1
a
history of head trauma that has caused concussion,
2
evidence of
poor performance on neuropsychological assessment of attention
or memory and
3
three or more of the following symptoms
occurring after head trauma and lasting at least three months:
mood changes, fatigue, difficulty sleeping, change in personality
and apathy and a significant decline in social or occupational
functioning resulting from injury.
7-9
There is increasing evidence that certain populations are at
greater risk of developing PCS, including the elderly, the very
young, women and those with a learning disability.
10-17
Concus-
sion can result from a wide variety of mechanisms including
sports, motor vehicle accidents, falls and trauma. The relationship
between development of PCS and mechanism of concussion is not
known. There is some evidence that there are gender differences
in the incidence of PCS from sports.
18
A recent narrative review
by Brook et al
19
found that women showed the greatest acute
neurological complications after concussions, including slower
reaction times, increased symptoms, worse memory function and
greater recovery time, compared with men. The longer recovery
time in women may also increase the risk of experiencing a second
concussion before symptoms have fully resolved, thus increasing
the risk for developing PCS.
20
Most research focuses on athletes,
but a few have evaluated gender differences in the non-athletic
community and also found that women are at a higher risk of
concussion and go on to develop PCS.
12,17
More recently, some
research is beginning to address gender differences in assault,
where 68% of women experiencing intimate partner-related injury
have experienced at least one mTBI and 44% have experienced
multiple mTBIs.
21,22
Age also appears to influence the prevalence of PCS. The
elderly appear to have a higher risk of developing PCS and have a
higher likelihood of never recovering.
12,17
In some studies, mTBI
has been related to higher mortality in the elderly after correcting
for factors such as patient demographics and dementia diag-
nosis.
23
In addition, falls are a growing concern among the
elderly, which puts them at greater risk for concussion and
potentially PCS.
24
There is also growing concern for PCS in
pediatric athletes, and the rate of sport-related concussion has
been increasing significantly in this population.
25
A recent study
on patients visiting a PCS clinic revealed that over half of the
patients with sport-related PCS were under the age of 18.
5
This
study had reported a higher than usual incidence of youth PCS
cases, defined as 18 years of age or younger, owing to inclusion of
clinic patients ranging from the ages of 11 and older, rather than
simply adult professional athletes alone.
5
Age and gender influence the risk of developing PCS.
12,17
Although there is some emerging evidence that there is a rela-
tionship between the mechanism of concussion injury and age or
gender, the nature of that interaction is largely unknown. As
treatment for PCS is not well developed, there is a need for
effective, targeted concussion prevention strategies and monitor-
ing of high-risk patients following an mTBI.
26
Multiple factors
contribute to the risk of developing PCS from concussion, and a
better understanding of these interactions is important when
developing strategies to aid in prevention. Therefore, our study
sought to better understand the interaction among variables such
as age, gender, mechanism of injury and concussion history in
patients with PCS so as to assist in the development of targeted
prevention strategies and more effective allocation of resources.
MATERIALS AND METHODS
Subjects
Patients with PCS were included from two sources:
1
apro-
spective biomarker PCS study that had completed enrollment
(recruited from the Canadian Concussion Centre), and
2
from clinical
charts of patients who presented to the University Health Network
Concussion Clinic from January 2010 to April 2016 for assessment
of persistent symptoms after a concussion. All participants (pro-
spective biomarker and clinical charts) included in this study com-
pleted a neurological examination, neuropsychological assessment
and neuroimaging. Patients identified in clinical charts were referred
by one of the following methods: a primary care provider or a spe-
cialist including neurologists and psychiatrists. Canadian Concus-
sion Centre research participants were originally recruited for
research purposes. There was no overlap between these two sources.
Modified DSM criteria were used in this study: all patients had three
or more symptoms for at least 3 months; disturbance caused sig-
nificant impairment in social or occupational functioning; and sig-
nificant decline from a previous level of functioning.
Inclusion criteria (prospective biomarker PCS study and ret-
rospective data) were as follows: patients diagnosed with PCS
using modified DSM-IV criteria (see above), with documented
mechanism of injury and age of index concussion.
8
History of
concussions was determined by the patient’s ability to recall
injuries caused by a blow to the head or body. There were no
restrictions for inclusion of PCS cases based on the number of
previous concussions. Patients seen in this adult PCS clinic had to
have been a teenager or older. No pediatric cases were included in
this study. Patients seen in this adult PCS clinic were between 17
and 81 years of age.
Exclusion criteria included the inability to recall the cause of
the index concussion, a history of neurological or developmental
disorder, psychiatric illness or other illness affecting the brain.
The Research Ethics Board of the University Health Network
(UHN) approved both studies (retrospective and prospective
biomarker). Consent was obtained from all participants in the
biomarker study, as outlined by the UHN research protocol. Eth-
ics approval was obtained for the retrospective data collection
from clinical charts.
Variables Analyzed
The following data were obtained from the prospective PCS
study and retrospective chart review: gender, age, number of
concussions, duration of PCS symptoms and mechanism of injury
of concussion that led to PCS. Patients were divided into two age
groups, 49 or less and 50 or more, in keeping with recent studies
of age-related outcomes following an mTBI.
27,28
Cause of con-
cussion was divided into five groups: falls, motor vehicle collision
(MVC), sport, assault and not otherwise specified (NOS). NOS
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included any accident one may experience at work or during daily
activities resulting in concussion such as bumping one’s head.
Statistical Analysis
Population demographics were described using proportions
and frequencies. χ
2
tests were used to compare the distribution of
the mechanism of injury between genders and between age
groups.
A log-linear model was used to describe the full set of rela-
tionships among age, gender, mechanism of injury and concus-
sion history. The full (all-interactions) model included
1
age,
gender, mechanism of injury or
2
age, gender, mechanism of injury
and concussion history. Simpler subsets of the model that dropped
certain two-, three- or four-way interactions, and that compared
the fit of the simpler models with the full model, were examined.
The final model was the simplest model that was not statistically
significantly different from the full model. Estimated odds ratios
(OR) were calculated to summarize the relationships between the
related variables in the model. All analyses were performed using
SPSS Statistics Software (version 23.0), R (version 3.4.0) and
Microsoft Excel (2016).
24
RESULTS
Patient Population
A total of 437 PCS cases were included for analysis (Table 1).
Of those 437 cases, 118 (27.0%) PCS cases were identified ret-
rospectively from clinic charts, whereas the latter 319 (73%) cases
were identified from a prospective biomarker study on PCS. The
PCS patient group comprised more men (251; 57.2%) than
women (186; 42.6%). There were more younger (≤49 years) (354;
81.0%) than old (>50 years) (83; 19.0%) PCS patients. Overall,
96 (22.0%) patients had PCS after a single concussion, whereas
341 (78.0%) had a history of multiple concussions. A greater
proportion of women (29.0%) had PCS after a single concussion
compared with men (16.7%), respectively (Table 2). A greater
proportion of older patients (43.9%) had PCS after a single con-
cussion compared with younger patients (17.0%), respectively
(Table 2).
χ
2
Analysis
There were many significant two-way interactions between
variables described in analyses 1-6. These interactions showed
significant differences between groups within the different
mechanisms of concussion. Non-significant differences between
groups within concussion mechanism were not included in the
analysis summary. Percentages and proportions are shown in
Table 1.
Analysis 1: Gender and Mechanism of Injury
There was a significant relationship between gender and the
mechanism of injury in PCS patients (p<0.01). There were a
greater proportion of women with concussions from falls and
MVC, and men with concussion from sport.
Analysis 2: Age and Mechanism of Injury
There was a significant relationship between age and
mechanism of injury in PCS patients (p<0.01). There were a
greater proportion of older patients with concussion from falls and
MVC, and younger patients with concussion from sport.
Table 1: Demographics of patients with post-concussion syndrome
Women (n=186) Men (n=251)
Variables <50 years 50 + years Total <50 years 50+ years Total
Total cases (n[%])*, # 143 (76.9%) 43 (23.1%) 186 (100%) 211 (84.1%) 40 (15.9%) 251 (100%)
Mechanism of injury (n[%])
Sport (n[%])*, # 65 (45.5%) 3 (7.0%) 68 (36.6%) 140 (66.4%) 13 32.5%) 153 (61.0%)
MVC (n[%])*, # 33 (23.1%) 14 (32.6%) 47 (25.3%) 21 (10.0%) 12 (30.0%) 33 (13.1%)
Fall (n[%])*, # 22 (15.4%) 20 (46.5%) 42 (22.6%) 13 (6.2%) 9 (22.5%) 22 (8.8%)
Trauma (n[%]) 8 (5.6%) 2 (4.7%) 10 (5.4%) 16 (7.6%) 1 (2.5%) 17 (6.8%)
NOS (n[%]) 15 (10.5%) 4 (9.3%) 19 (10.2%) 21 (10.0%) 5 (12.5%) 26 (10.4%)
Total 143 (100%) 43 (100%) 186 (100%) 211 (100%) 40 (100%) 251 (100%)
MVC =motor vehicle collision; NOS =not otherwise specified.
p-values <0.05 are considered statistically significant and will be indicated by a single asterisk (*) if there is a significant result between genders (men vs.
women).
p-values <0.05 are considered statistically significant and will be indicated by the hashtag (#) if there is a significant result between age groups (young
[<50 years) vs. old [50 + years]] in the total population (men and women).
Table 2: Concussion demographics for post-concussion
syndrome patients with a single concussion
Single
Men 42 (16.9%)
Women 54 (29.0%)
Young 60 (16.9%)
Old 36 (43.3%)
Sport 16 (7.2%)
Fall 26 (40.6%)
MVC 37 (46.2%)
Other (assault + NOS) 17 (23.6%)
MVC =motor vehicle collision; NOS =not otherwise specified.
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Analysis 3: Age and Mechanism of Injury in Women
There was a significant relationship between age and
mechanism of injury in women with PCS (p<0.01). There were a
greater proportion of older women with concussions from falls
and younger women with concussion from sport.
Analysis 4: Age and Mechanism of Injury in Men
There was a significant relationship between age and
mechanism of injury in men with PCS (p<0.01). There were a
greater proportion of older men with concussion from falls and
MVC, and younger men with concussion from sport.
Analysis 5: Gender and Mechanism of Injury in Young Patients
There was a significant relationship between gender and
mechanism of injury in young patients with PCS (p<0.01). There
were a greater proportion of younger women with concussion
from falls and MVC, and younger men with concussion
from sport.
Analysis 6: Gender and Mechanism of Injury in Old Patients
There was a significant relationship between gender and
mechanism of injury in older men and women with PCS
(p<0.01); however, post-hoc analysis revealed only trends.
Log-Linear Modeling
Conditional Independence of Age and Gender Given
Mechanism
Most of the log-linear models contained significant two-way
interactions of at least one of the demographic variables and
mechanism of injury, as stated in Analyses 1 and 2.
Analysis 1: Analysis of Age, Gender and Mechanism of Injury
The simplest model with a good fit to describe the data is the
conditional independence model wherein there was a significant
relationship between mechanism of injury and age (p<0.001) and
mechanism of injury and gender (p<0.001). As NOS and assault
had a very low number of cases, in addition to a similar distribu-
tion of age and gender, they were combined to create a single
group termed “other.”The relationship between age and gender in
patients with PCS disappears once the mechanism of injury
is known.
Analysis 2: Analysis of Age, Gender, Mechanism of Injury
and Concussion History
When concussion history is included as a fourth variable in the
log-linear model, the simplest good-fitting model is also condi-
tional independence, where there is a significant relationship
between mechanism of injury and age (p<0.01), mechanism of
injury and gender (p<0.01) and mechanism of injury and con-
cussion history (p<0.01). The relationship between age, gender
and concussion history in patients with PCS disappears once the
mechanism of injury is known.
Odds Ratio
There are interactions between gender and mechanism of
injury in those having PCS, which are independent of age. The
relative frequency of women having PCS if the mechanism of
injury is a fall is greater than the frequency of those being a male
and having PCS from a sport (OR =4.24; 95% confidence interval
[CI]: 2.38-7.75), MVC (OR =1.33; 95% CI: 0.68-2.63) or “other”
(OR =2.86; 95% CI: 1.41-5.56), as shown in Table 3 (p<0.001).
There was also a greater relative frequency of women having PCS
if the mechanism of injury was an MVC than men having PCS
from a sport or cause of injury being other (p<0.001).
There are interactions between age and mechanism of injury in
those having PCS, which are independent of gender. There was a
greater relative frequency of older patients with PCS with con-
cussion from fall compared with younger PCS patients with
concussion from a sport injury (OR =11.11; 95% CI: 5.56-25.0),
MVC (OR =1.72; 95% CI: 0.87-3.45) or “other”(OR =4.17;
95% CI:1.89-9.09), respectively (p<0.001). All values are shown
in Table 4. Similarly, there was greater relative frequency of being
older and having PCS if the mechanism of injury was from an
MVC than if being younger and having concussion from sport or
other (p<0.001).
Finally, there are interactions between concussion history and
mechanism of injury in those having PCS, which are independent
of age or gender. There was a greater relative frequency of having
PCS after a single concussion if the mechanism of injury was from
an MVC rather than if the mechanism of injury was sport (OR =
10.92; 95% CI: 5.67-21.9), fall (OR =1.25; 95% CI: 0.65-2.44)
or “other”(OR =2.78; 95% CI: 1.38-5.60), as shown in Table 5
Table 3: Odds ratios for being a woman with post-concussion
syndrome, compared with male patients
Risk 95% CI p-Value
Fall vs. sport 4.24 2.38-7.75 <0.001*
Fall vs. MVC 1.33 0.68-2.63
Fall vs. other 2.86 1.41-5.56
MVC vs. sport 3.16 1.87-5.41 <0.001*
MVC vs. other 2.13 1.10-4.00
Other vs. sport 1.50 0.85-2.59 0.15
CI =confidence interval; MVC =motor vehicle collision.
p-values <0.008 are considered statistically significant after correcting for
multiple comparisons and will be indicated by an asterisk (*).
Table 4: Odds ratios for being a young patient with
post-concussion syndrome, compared with an older patient
Risk 95% CI p-Value
Fall vs. sport 11.11 5.56-25.0 <0.001*
Fall vs. MVC 1.72 0.87-3.45
Fall vs. other 4.17 1.89-9.09
MVC vs. sport 6.67 3.26-12.5 <0.001*
MVC vs. other 2.38 1.11-5.26
Other vs. sport 2.70 1.19-6.25 0.015
CI =confidence interval; MVC =motor vehicle collision.
p-values <0.008 are considered statistically significant after correcting for
multiple comparisons and will be indicated by an asterisk (*).
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(p<0.001). Sport was least likely to be associated with PCS after
a single concussion (p<0.0001).
DISCUSSION
Multiple factors contribute to the risk of developing PCS from
concussion, and a better understanding of these interactions is
important when developing strategies to aid in prevention. The
present study assessed the features of PCS cases collected from
clinical charts and a prospective biomarker study, and then ana-
lyzed interactions between age, gender, concussion history and
mechanism of injury. There were significant two-way associa-
tions with age, gender and mechanism of injury in our analysis.
Women and older patients with PCS were more likely to have
been injured in a fall or MVC compared with men and younger
patients with PCS, who were more likely to have been injured in
sport. In our log-linear analysis, interactions between age, gender
and concussion history were conditionally dependent on
mechanism of injury, but unrelated to one another. Again, women
and older patients with PCS were more likely to have been injured
in a fall or MVC compared with men and younger patients with
PCS, who were more likely to have been injured in sport. Fur-
thermore, our sample included more patients with PCS after a
single concussion when the mechanism of injury was an MVC,
whereas there were more patients with PCS after multiple con-
cussions when the mechanism of injury was sport. Finally, there
were more women who had PCS after a single concussion, com-
pared with men, who were more likely to have PCS after sus-
taining multiple concussions. Our results indicate that specific
patient demographics in PCS patients are associated with different
mechanisms of injury, which may help predict those who could be
at risk. As PCS is a growing concern worldwide, because it is
associated with tremendous psychological, physical and financial
burden, targeted prevention strategies should be envisioned.
There is increasing evidence that women are vulnerable to
concussion. Among adult athletes, women have been reported to
show an increased number and severity of symptoms after con-
cussion.
10
Women seem to be at higher risk for persistent symp-
toms, leading to the development of PCS,
17,29
have a greater
number of symptoms and are more likely to develop PCS after a
single concussive event.
4
This may indicate that women are more
susceptible to concussions and consequently PCS than men.
However, this may also suggest that women are more proactive in
their health care and are therefore more likely to seek consultation
after concussion compared with men.
30,31
Interestingly, gender
differences in PCS symptoms are not apparent in pediatric ath-
letes, and only begin to appear in young adulthood.
29
Additionally, our study has shown that there is a greater rela-
tive frequency of women with PCS following mTBI from either a
fall or assault. One reason for the higher prevalence of women
with PCS after a fall is owing to the increased number of falls in
women, putting them at a greater risk of PCS from falls compared
with men.
31
Women are also at greater risk of mTBI from assault,
which puts them at a higher risk for developing PCS.
21,22
An issue
with current data is the underrepresentation of concussion from
intimate partner abuse owing to the lack of reporting from abuse
and the lack of recognition of persistent concussive symptoms in
women who have been subjected to intimate partner abuse.
21
This
clearly necessitates greater education and awareness, which can
aid in the reporting and identification of intimate partner abuse.
Our study also revealed that more women than men and more
older than younger people had PCS after an MVC. A previous
study has shown that recovery rates from concussion were pro-
longed after MVC compared with sport, and there was greater
symptom severity.
32
The cause of greater PCS in women from
MVC is unknown as men are more often involved in MVC than
women.
33,34
It may be that injuries in men from MVC are more
serious than concussion
33,34
or that in MVC, like sport, women
seem to be at an elevated risk of developing post-concussion
symptoms and PCS. It is not surprising that more elderly partici-
pants have PCS from MVC as statistics show that people aged 70
or older have a higher accident rate per kilometer driven than any
other age group, except young male drivers.
35
It is well recog-
nized that there are age-related changes in cognitive functioning
and as driving involves integration of visual, cognitive and psy-
chomotor skills, cognitive decline can increase the risk of MVC,
and consequently concussions.
36,37
Our results are in keeping
with those from Cassidy et al,
28
whereby they reported that a
majority of MVC-induced mTBI occurred in females suffering an
MVC and that there was delayed recovery of MVC-induced mTBI
symptoms in those older than 50.
In addition, many MVC cases in our study had PCS after a single
concussive event versus those who had PCS from sport. This may be
owing to the higher impact of an MVC-induced mTBI compared
with the impact of a sport-induced mTBI. Additionally, this may be
because many of our PCS cases with a sport-induced injury had a
history of multiple injuries, and therefore they were less likely to be
represented among those categorized as having had a single con-
cussion. Finally, it may be that MVCs are more likely to be reported,
and those sustaining a sport-related injury are under greater pressure
to continue competing.
38
Similar to others, we found that PCS from falls was more
common in the elderly.
12,17,39
Previous studies have also sug-
gested that there is an increased risk of falls, and subsequently
mTBI owing to cognitive impairment in the elderly.
40,41
Persistent
symptoms have also been attributed to less cognitive reserve in the
elderly.
41
In a recent mTBI study, age-related differences were
observed in functional MRI activation in the frontal and parietal
brain regions, while performing a working memory task.
27
Younger participants showed hyper-activation of cortical
regions while performing a working memory task, which resolved
at follow-up. However, elderly patients showed hypo-activation
following injury and did not show any improvement at follow-up.
Table 5: Odds ratios for having post-concussion syndrome
after a single concussion, compared with multiple
concussions
Risk 95% CI p-Value
MVC vs. sport 10.92 5.67-21.9 <0.001*
MVC vs. fall 1.25 0.65-2.44
MVC vs. other 2.78 1.38-5.60
Fall vs. sport 8.68 4.31-18.0 <0.001*
Fall vs. other 2.21 1.06-4.63
Other vs. sport 3.92 1.86-8.33 <0.001*
CI =confidence interval; MVC =motor vehicle collision.
p-values <0.008 are considered statistically significant after correcting for
multiple comparisons and will be indicated by an asterisk (*).
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Only the younger patients showed a reduction in PCS symptoms.
It is possible that age-related reduction in neuroplasticity/com-
pensation prevents a return to normal neural activity in the elderly.
One caveat to their study was the short follow-up time (6-weeks)
following the baseline assessment, which may have been inade-
quate to show recovery in the elderly. Alternatively, it is possible
that older adults endorse a greater number of co-morbidities, and
therefore symptoms appeared to have persisted for a greater
duration of time.
42
Some studies have also shown increased
mortality after mTBI in the elderly, even after correcting for age,
education and a diagnosis of dementia.
23
Our study does not come without limitations. One limitation of
our study was the relatively small number of older patients. This
may be owing to older people having more severe consequences
from a head injury and thus more likely to suffer contusion, bleed
or death. Additionally, the study required patients to recall when
they had the concussion or the mechanism of injury, which may
have been difficult with older patients having a cognitive
impairment. However, even with memory impairment, patients
can usually recall the mechanism of injury; thus, only those with
severe dementia would be excluded. Another explanation for our
small sample size may be owing to our exclusion criteria, which
removed any patient who had a co-morbid neurological/psycho-
logical disorder because of the symptom overlap with PCS.
However, we have excluded these participants as it is currently
debated whether overlapping pre- and post-injury psychiatric ill-
nessess enable an accurate diagnosis of PCS. Therefore, removal
of these participants has increased the accuracy with which a
patient could be diagnosed with PCS. A second limitation is that
the subjects came from two sources: a prospective study of PCS
patients at the Canadian Concussion Center and patients from a
Concussion Clinic. This approach was used to increase the overall
sample size, but this limited the number of variables and statistical
tests that could be implemented. Furthermore, as DSM-IV criteria
require neuropsychological assessment, we have not conducted
any validity testing and it is possible that a patient may have not
been motivated during the test and may have put insufficient effort
in answering the questions. Finally, a lack of control group who
experienced concussion without developing PCS precludes us
from calculating the true risk of developing PCS in the context of
different mechanisms of injury. Therefore, future work should try
to gather data on all patients presenting to ER and/or family doctor
to see which mechanisms of injury are associated with the highest
risk of developing PCS and how this differs according to the
various demographic factors.
CONCLUSION
In summary, both age and gender have unique interactions
with mechanisms of injury in those with PCS. These results sug-
gest that targeted prevention strategies for concussion injuries are
warranted as different mechanisms of injury seem to be associated
with a greater risk of PCS in different populations. These per-
sisting post-concussive symptoms are associated with emotional/
psychological distress, loss of productivity and financial hard-
ships, highlighting the importance of prevention strategies.
43
Research into tailoring prevention programs to specific popula-
tion, such as prevention of sport-related concussions in schools,
may help reduce the risk of concussion and subsequent PCS.
ACKNOWLEDGMENTS
The authors thank all the participants for their contribution to
our study.
FUNDING
The Toronto Western and General Hospital Foundation and
Ontario Brain Institute provided funding for the study.
DISCLOSURE
BV, GT, AT, RW, CT and MCT have no conflicts of interest to
declare.
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