Should Young Children with Traumatic Brain Injury Be Compared with Community or Orthopedic Control Participants?

Abstract

Pediatric traumatic brain injury (TBI) research depends on comparisons of profiles and outcomes between brain-injured individuals and groups consisting either of injured controls (e.g., orthopedic injuries, OI) or uninjured, typically developing children recruited from the community (community controls, CC). Children with OI are thought to provide optimal comparisons for individuals with TBI because they share injury-related experiences and pre-morbid characteristics; however, a study by Mathias and colleagues (2013)¹ in adults has called into question the added value of injury control groups in TBI research. The comparability of these control groups has not been established in young children. Seventy-two children with OI and 84 CC aged between 18 and 60 months were compared on a range of demographic variables, developmental and medical history, pre-injury behavioral and adaptive profiles, as well as on measures of adaptive functioning, behavior, family functioning, post-concussive symptoms, and cognition (intellectual functioning, verbal abilities, executive functioning, social cognition) 6 months after the OI. There were no statistically significant differences between the OI and CC groups on any of the variables tested, whether they related to pre-injury or post-injury characteristics. The findings are applicable to studies seeking to identify appropriate control groups in the context of preschool TBI research, and suggest no clear advantage in recruiting OI controls based on the variables studied and the methodology used. However, further work is necessary to verify additional factors and outcomes relevant to pediatric TBI research, as well as to compare outcomes between these two groups at more acute stages (i.e., prior to 6 months post-injury).

Introduction

Childhood traumatic brain injury (TBI) is a prevalent health problem that can lead to physical, cognitive, behavioral, and social changes in development.² In its mildest form (mild TBI [mTBI] or “concussion”), alterations in functioning are typically reported to be more transient and less pervasive than after more severe injuries, leading to good prognosis,^{3

–13} although some data suggest that a minority of children may suffer from more chronic difficulties and persistent symptoms.^14,15 Some controversy exists, however, as to whether changes in functioning after mTBI are brain-injury specific, or whether they represent more general injury effects that may also be present in other traumatically injured groups, such as those with orthopedic injuries (OI).¹⁶ Alternately, it has also been suggested that difficulties, or more protracted recovery periods following mTBI, may simply reflect the presence of problems that pre-date injury.^13,17

Related to this issue, there is a debate as to what type of control group offers the best comparative approach for accurately reporting mTBI outcomes, and controls for potential pre-morbid problems and the medical experience. Non-injured children recruited from the community (“community controls” [CC] or “typically developing controls”) are most often used in pediatric mTBI studies, notably because they are numerous, accessible, and less costly to recruit. In addition, they are thought to be representative of population-level functioning and standardized test norms,¹ and offer the opportunity to compare children with TBI with the peers they are likely to be contrasted with in daycare, school, recreational, and community settings. OI control groups, on the other hand, have the advantage of being more comparable with those with mTBI at an experience-level because they go through similar medical processes (e.g., presentation to the Emergency Department, radiological exams, minor medical interventions, medication for pain, stress, etc.).¹² Children who sustain OI are also thought to present similar pre-morbid (e.g., attention problems, behavior) characteristics to those who incur mTBI, which may place them at similar risk for sustaining injury.^11,18,19 Demographic factors (e.g., socioeconomic status, congested living) and parenting practices (e.g., parental alcohol misuse, psychiatric history, unsupervised play) may also increase the risk of accidental injuries.^20
–22 However, despite studies reporting elevated pre-morbid attention and behavioral problems in children who sustain brain injury,^23
–25 there is little direct evidence showing that the prevalence is comparable to that of other injury groups.

In one of the largest studies of pediatric mTBI outcome to date, Babikian and colleagues found that when the effects of pre-injury risk factors and general injury experience are controlled for by comparing children with mTBI with an “other injury” control group, there was no evidence of long-term cognitive impairment in the mTBI group.¹⁰ However, children with mTBI did show performance differences when compared with a non-injury control group, suggesting a general injury rather than a brain injury-specific effect. This and other studies^{e.g.,12,26,27} support the idea that injured control groups are the most methodologically sound choice for pediatric mTBI research.

Mathias and colleagues revisited the TBI control group debate in an adult population by directly investigating the comparability of community and OI control groups aged 18–80 years across a range of demographic, background, psychosocial, and cognitive variables, and found no statistically significant group differences other than on rate of alcohol use, which did not correlate with common variables of interest in TBI research.¹ The authors concluded that there appears to be no clear advantage in recruiting an injury control group in adult TBI research. It is possible, however, that the comparability of adult control groups does not extend to pediatric populations, as factors of influence are likely to be different. For instance, children are more subject to environmental influences such as parental education and family functioning than are adults. Children also typically have greater inter-individual variability in functioning because of normal variations in developmental trajectories and reliance on more diffuse cognitive and social brain network.²⁸ Differences between the two types of control groups may also be lessened in adults because of the greater adherence of adults to societal norms and expectations, and their increased ability to regulate and compensate for potential behavior or pre-morbid problems.

Children who sustain TBI before the age of 6 (i.e., preschoolers) represent a particular portion of the TBI population in which the choice of control group is especially relevant to study. First,TBI during this period is highly prevalent, with birth cohort data indicating an annual TBI rate of 1.85 per 100 children aged 0 to 5 years, compared with rates of <1.17 in other pediatric age groups.²⁹ Second, children of this age who sustain injury are likely to be highly vulnerable to adverse outcomes because any disruption in the acquisition or consolidation of rapidly emerging skills has the potential to set them back from typical developmental trajectories.^30,31 Third, preschoolers have short developmental histories in comparison with older pediatric age groups and adults and therefore less is known about their pre-morbid status. To date, researchers have used either CC or OI groups exclusively in their comparisons of preschoolers who sustain TBI with control participants. Whether they have favored CC^32,33or opted for OI³⁴ groups, analyses have tended to show adequate matching on standard demographic variables such as age and socioeconomic status. However, these basic comparisons do not inform on other potential areas of dissimilarity between groups, such as behavior, family functioning, or cognition.

The objective of this study was therefore to address the question of optimal control group selection in pediatric TBI research, with a particular focus on those that are the most vulnerable, i.e., children under 5 years of age. Specifically, we aimed to compare OI controls with CC between the ages of 18 and 60 months on a range of variables relevant to development and to TBI, including demographics, developmental and medical history, behavior and adaptive functioning, family factors, post-concussive symptoms, global cognition, and aspects of social cognition and executive functioning.

Methods

Participants

As part of a prospective, longitudinal study on the consequences of early TBI, two groups of control participants were recruited and compared: 72 children who sustained OI were identified at an tertiary urban Emergency Department and 84 typically developing children were recruited from the community (CC). Inclusion criteria for the OI group were (a) age at injury between 18 and 60 months; (b) limb trauma leading to a final diagnosis of simple fracture, sprain, contusion, or unspecified trauma to an extremity. The CC were aged between 24 and 66 months in order to be of comparable age to the OI at post-injury assessment time-points. The following exclusion criteria were applied for all participants; (a) diagnosed congenital, neurological, developmental, psychiatric, or metabolic condition; (b) less than 36 weeks of gestation; (c) prior TBI; and (d) non-fluent in French or English.

Procedure

This study was approved by the Sainte-Justine Hospital Research Ethics Board. Recruitment of children who sustained OI took place in the Emergency Department at Sainte-Justine Hospital between 2011 and 2015. A research nurse approached potentially eligible participants. Once they agreed to participate, the research coordinator mailed a consent form and a pre-injury questionnaire booklet along with a sociodemographic questionnaire. The primary caregiver (90% mothers) was asked to answer the questionnaire based on their child's functioning prior to the injury. Six months later, children with OI were invited to the laboratory for a cognitive assessment and the primary caregiver completed the same questionnaire booklet (without the sociodemographic questions) along with a questionnaire pertaining to post-concussive symptoms.

The CC were recruited in daycare centers by research assistants. Given the absence of injury, the CC were tested right after recruitment, and the primary caregiver (89% mothers) completed all the questionnaires.

Measures

1. Questionnaires

ABCs Demographic Questionnaire. The primary caregiver completed this in-house developmental and demographic questionnaire. It includes information on the child's gender, handedness, ethnicity, birth characteristics, and developmental and medical history. In addition, socioeconomic status (SES) was calculated using the Blishen Socioeconomic Status Scale,³⁵ which attributes a score based on parents' occupation. Parental education was also calculated by averaging both parents' highest educational attainment, ranging from 1 (doctoral level) to 8 (less than 7 years of school). When parental occupation and/or highest educational attainment was available for only one parent, or in the case of single parent families, no average was computed. If a child lived with one biological parent and a step-parent, we used the step-parent's information was used in the average.

Adaptive Behavior Assessment System (ABAS). ³⁶ The ABAS, 0–5 year version, is a parent-report questionnaire that provides a comprehensive assessment of everyday adaptive functioning in 10 skill areas (communication, community use, functional academics, home living, health and safety, leisure, self-care, self-direction, social, and motor). The parent must indicate the frequency at which the behavior is demonstrated on a 4-point scale (0 = Is not able, 1 = Never when needed, 2 = Sometimes when needed, 3 = Always when needed). The Global Adaptive Composite (GAC), the Social Composite, the Practical Composite, and the Conceptual Composite are reported. A higher standard score (M = 100, SD = 10) is indicative of better adaptive skills.

Child Behavior Checklist (CBCL). ³⁷ The CBCL for ages 1.5–5 years is a 100-item checklist used to assess the presence of internalizing and externalizing behavior problems. The primary caregiver must rate their child on a 3-point scale (0 = Not true, 1 = Somewhat or sometimes true, 2 = Very true or often true). The internalizing problems score (Emotionally reactive, Anxious/depressed, Somatic complaints, and Withdrawn subscales) and the externalizing problems score (Attention problems and Aggressive behavior subscales) are reported. A higher standard score (M = 50, SD = 10) indicates more behavioral problems.

Family Functioning Device (FAD). ³⁸ The General Functioning (GF) subscale of the FAD includes 12 items pertaining to overall satisfaction with family functioning. Each statement is rated on a 4-point scale ranging from 0 to 3. A higher score indicates poorer family functioning.

Dyadic Adjustment Scale (DAS). ³⁹ The brief 4-item version of the DAS was completed by the primary caregiver as a measure of couple satisfaction. Each item is rated on a 6-point scale ranging from 0 to 5, and a higher score indicates higher marital satisfaction.

Parental Stress Index (PSI). ⁴⁰ This questionnaire is designed to measure stress experienced in the parental role. A brief version (24 items) was administered in which the parent must answer on a 5-point scale ranging from 1 to 5. The scores from the Parental distress (PD) and the Parent-child dysfunctional interaction (PCDI) subscales are reported. The PD subscale pertains to the parent's perception of his or her own behavior (e.g., marital conflict, perceived competence, depression), whereas the PCDI subscale indicates whether the parent perceive his or her interactions with the child as satisfying or not.

Post-concussive Symptom Interview (PCS-I). ⁴¹ The PCS-I is a symptom checklist administered orally to parents. It evaluates the presence of 15 post-concussive symptoms in cognitive, somatic, affective, and sleep domains. Parents must indicate if the symptoms were present (score of 1) or absent (score of 0) in their child over the past week and the past 6 months.

2. General intellectual functioning

Global intellectual functioning and verbal abilities were measured for all participants. Children between 24 and 30 months at the time of the assessment were evaluated using the Cognitive and Language subscales from the Bayley Scales of Infant Development (Bayley-III),⁴² and children older than 31 months completed the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III).⁴³ The Bayley-III Cognitive composite and the Global Index of the WPPSI-III were used as indicators of general intellectual functioning, whereas the language composite of the Bayley-III and verbal IQ from the WPPSII-III were used to reflect verbal abilities. Percentile ranks are reported, allowing direct comparison of the two cognitive tools.

3. Social cognition

False belief understanding.^44,45 Children are presented a peep-through picture book with deceptive elements (e.g., what appears to be an eye peeping through turns out to be a spot on a snake's back) to measure false belief understanding, a subcomponent of theory of mind. They are then asked to recall their own initial false belief about what they saw and to predict another person's false belief. Scores vary between 0 and 2.

Discrepant desires and Desires tasks.^45
–47 Depending on their age, children completed one of two developmentally appropriate tasks measuring desires reasoning, a subcomponent of theory of mind. Those aged 24 to 35 months were administered a task during which they must choose between two foods, one typically liked by children (e.g., cookies) and one that is generally less preferred (e.g., celery). Then, the experimenter expresses a preference for the children's non-preferred food and asks for another food item. The goal of the task is to assess whether children will answer egocentrically or will consider the experimenter's preferred food. A total of four food combinations are presented, for a maximum of four points. Children aged 36 months and older completed a measure of their understanding of how fulfilled and unfulfilled desires might affect a character's feelings in a story. The stories describe a character's search for a desired object and at the end of the story, children are asked to speculate whether the character is happy or sad. Six stories are presented, for a maximum score of 6 points.

4. Executive functions

Tower of Hanoi (planning).⁴⁸ Children were administered Welsh's simplified version of this classic planning task. Three different sized disks must be moved among three pegs to recreate a goal configuration in a minimum number of moves by always placing a small disk over a larger one. Children were asked to recreate six towers, for a maximum of 6 points.

Delay of gratification (inhibition).⁴⁹ Children must make a series of choices as to whether they want a smaller immediate reward or a larger delayed reward. Awards are crackers, coins, and stickers presented in small plastic containers. For example, the child must choose between a cracker to eat now, or six crackers to eat later “when all games are completed and you will return home.” One point is awarded every time the child selects the delayed reward for a maximum of 9 points.

Spin the pots (working memory).⁵⁰ Depending on their age, children are presented with 8–12 visually distinct boxes and 6–10 stickers. Stickers are placed in the boxes and children are encouraged to search for them. The boxes are rotated from one trial to the next so that the child must keep in mind where they have searched and found stickers previously. The task ends when the child has found all the stickers or when the maximum number of spins has been reached (12, 16, or 20 spins for respectively 8, 10, and 12 boxes). A final score is calculated as the proportion of stickers found to the total number of spins required to find all stickers.

Conflict scale (cognitive flexibility).⁵¹ This task consists of four levels of increasing difficulty (Categorization/Reverse Categorization, Dimensional Change Card Sort (DCCS)–Separated, DCCS–Integrated, and DCCS–Advanced), and children begin the task at the appropriate level for their age. Children are asked to categorize items, either plastic animals or cards, according to a rule, and if they succeed on 5 trials out of 6, the rule is changed. For example, children are instructed to sort cards according to color (red or blue). Then, the experimenter announces that they will stop playing the “color game” and now play the “shape game.” Children must then sort cards according to shape (star or truck). There are 12 trials per level, for a maximum of 48 points.

Shape stroop (inhibition).^52,53 First, children are shown six cards depicting three fruits (three large and three small fruits). Children are asked to identify each fruit (e.g., “Show me the big apple”). Then, children are shown three cards, each depicting a small fruit embedded in a large fruit, and ask to point to each small fruit. A score out of 3 possible points is calculated.

Statistical analyses

All analyses were conducted using IBM SPSS Statistic Version 21 (SPSS Inc., Chicago, IL). Independent sample t tests were conducted for all continuous variables and chi-square (X ²) tests were conducted for all categorical variables. To be considered different, the group difference had to have a p value of <0.05 on the outcome variables. Additionally, effect sizes were calculated using Cohen's d for continuous data and Cramer's V for categorical data. Available-case analyses were performed, such that sample sizes ranged between 58 and 72 for the OI, and between 64 and 84 for the CC. Data were missing when the parents did not complete the questionnaire booklet, the cognitive assessment could not be performed due to lack of cooperation, or when participants from the OI group dropped out before the 6-month post-injury time-point.

Results

As displayed in Table 1, the OI and CC groups did not differ in terms of their age at assessment, socioeconomic status, parental education, gender, handedness, language, or ethnicity.

Table 1.

Demographic Characteristics

	OI	CC
	M (SD)	M (SD)	Difference	95% CI	t	p	d
Age at assessment, months	40.98 (11.20)	43.29 (11.65)	−2.09	−5.91 to 1.73	−1.09	0.28	0.18
SES	57.75 (13.65)	59.37 (12.07)	−1.62	−5.78 to 2.55	−0.77	0.44	0.13
Parental education	3.03 (1.02)	2.85 (0.82)	0.18	−0.11 to 0.47	1.22	0.23	0.19

	N (%)	N (%)			X²	p	V
Gender [male]	34 (52.8)	43 (48.8)	-	-	0.24	0.62	0.04
Handedness [right-handed]	47 (78.3)	62 (78.5)	-	-	2.17	0.54	0.13
Assessment language [French]	59 (96.7)	84 (100.0)	-	-	2.79	0.10	0.14
Ethnicity [Caucasian]	54 (78.3)	66 (80.5)	-	-	3.36	0.50	0.15

CC, community controls; CI, confidence interval; OI, orthopedic injuries; SD, standard deviation; SES, socioeconomic status.

In addition, there was no difference between the two groups in terms of developmental and medical history (Table 2). When presence of medical conditions was considered, only those that were exhibited by at least two participants in the sample were reported. Eye, ear, nose, and throat problems, gastrointestinal problems, and pulmonary problems were retained in the analyses, and the frequency was comparable in the two groups.

Table 2.

Developmental and Medical History

	OI	CC
	M (SD)	M (SD)	Difference	95% CI	t	p	d
Birth weight	3377.60 (609.40)	3498.27 (639.07)	−120.67	−326.37 to 85.03	−1.16	0.25	0.19
Birth length	49.82 (6.30)	50.08 (7.85)	−0.26	−2.70 to 2.19	−0.21	0.84	0.04
Apgar #1	8.42 (1.22)	8.46 (1.29)	−0.03	−0.47 to 0.40	−1.16	0.88	0.03
Apgar #2	9.06 (1.16)	9.02 (1.03)	0.05	−0.34 to 0.44	0.25	0.80	0.04
Age at first words	11.20 (3.97)	11.23 (3.22)	−0.03	−1.23 to 1.17	−0.04	0.97	0.01
Age at first steps	12.59 (2.37)	12.12 (4.66)	−0.52	−1.75 to 0.70	−0.84	0.40	0.14

	N (%)	N (%)			X ²	p	V
Pregnancy – smoking	3 (4.2)	2 (2.5)	-	-	0.37	0.55	0.05
Pregnancy – drinking	2 (2.9)	5 (6.1)	-	-	0.90	0.34	0.08
Pregnancy complications^a	28 (39.4)	22 (26.8)	-	-	2.75	0.10	0.13
Birth complications^b	17 (23.9)	13 (16.0)	-	-	1.49	0.22	0.10
Birth disorders^c	22 (31.0)	20 (24.7)	-	-	0.75	0.39	0.07
Eye, ear, nose, throat problems	16 (22.5)	11 (13.4)	-	-	2.18	0.14	0.12
Gastrointestinal problems	3 (4.2)	2 (2.4)	-	-	0.38	0.54	0.05
Pulmonary problems	3 (4.2)	4 (4.9)	-	-	0.04	0.85	0.02
Currently taking medication	1 (1.4)	4 (5.0)	-	-	1.50	0.20	0.10

Pregnancy complication include gestational diabetes, preeclampsia, bleeding, placental abruption, placenta previa, anemia, Rh incompatibility, and infection.

Birth complication include abnormal presentation, prolonged labor, umbilical cord compression, cesarean, and assisted birth with forceps or ventouse.

Birth disorders include jaundice, cyanosis, fœtal distress, breathing difficulties, and hypoglycemia.

CC, community controls; CI, confidence interval; OI, orthopedic injuries; SD, standard deviation.

As can be seen in Table 3, children in the two groups did not differ on behavioral (ABAS and CBCL) or family characteristics (FAD, DAS, and PSI), as reported by the primary caregiver. These results were observed when analyzing both pre-injury and post-injury characteristics for the OI group. Only the difference for pre-injury (p = 0.08, d = 0.29) and post-injury (p = 0.05, d = 0.33) ABAS Conceptual scores approached statistical significance, though effect sizes were small. Because the ABAS Conceptual scale approached statistical significance, we verified the sub-scores and no significant group differences were found for the Communication, Functional Academics, or Self-Direction subscales (p > 0.05). No group differences were found on any of the CBCL subscales and total scores.

Table 3.

Behavioral and Family Characteristics

	OI	CC
	M (SD)	M (SD)	Difference	95% CI	t	p	d
Behavior
Pre-injury ABAS-GAC	102.63 (12.85)	98.41 (11.84)	−1.72	−5.67 to 2.22	−0.86	0.39	0.14
Post-injury ABAS-GAC	96.51 (11.49)		−1.90	−5.83 to 2.03	−0.96	0.34	0.16
Pre-injury ABAS-Social	102.63 (14.01)	104.07 (16.04)	−1.44	−6.29 to 3.41	−0.59	0.56	0.10
Post-injury ABAS-Social	104.18 (13.59)		0.11	−4.95 to 5.17	0.04	0.97	0.01
Pre-injury ABAS-Practical	91.08 (13.83)	91.60 (13.48)	−0.51	−4.88 to 3.86	−0.23	0.82	0.04
Post-injury ABAS-Practical	90.92 (12.46)		−0.68	−5.07 to 3.71	−0.31	0.76	0.05
Pre-injury ABAS-Conceptual	97.55 (12.37)	100.73 (9.76)	−3.18	−6.72 to 0.36	−1.77	0.08	0.29
Post-injury ABAS-Conceptual	97.22 (11.67)		−3.51	−7.01 to 0.05	−1.95	0.05	0.33
Pre-injury CBCL^a-Internalizing	45.89 (10.07)	47.19 (10.93)	−1.30	−4.67 to 2.06	−0.77	0.45	0.12
Post-injury CBCL-Internalizing	48.44 (10.06)		1.25	−0.27 to 4.77	0.70	0.48	0.12
Pre-injury CBCL-Externalizing	47.94 (9.38)	48.71 (9.87)	0.77	−3.85 to 2.31	−0.49	0.62	0.08
Post-injury CBCL-Externalizing	50.00 (9.25)		1.29	−1.91 to 4.49	0.80	0.43	0.13
Family characteristics
Pre-injury FAD	1.63 (0.45)	1.56 (0.40)	0.07	−0.06 to 0.21	1.06	0.29	0.17
Post-injury FAD	1.67 (0.48)		0.11	−0.03 to 0.26	1.48	0.14	0.26
Pre-injury DAS	3.90 (0.92)	4.11 (0.88)	−0.22	−0.51 to 0.08	−1.46	0.15	0.24
Post-injury DAS	4.03 (0.74)		−0.08	−0.36 to 0.19	−0.59	0.56	0.10
Pre-injury PSI-PD	1.98 (0.65)	2.08 (0.66)	−0.10	−0.31 to 0.11	−0.92	0.36	0.13
Post-injury PSI-PD	1.96 (0.69)		−0.12	−0.34 to 0.10	−1.05	0.30	0.18
Pre-injury PSI-PCDI	1.47 (0.37)	1.45 (0.42)	0.02	−0.11 to 0.15	0.31	0.76	0.05
Post-injury PSI-PCDI	1.53 (0.43)		0.08	−0.07 to 0.22	1.07	0.29	0.18

CBCL t scores are reported. T scores above 65 are considered “borderline,” and T scores above 70 are “in the clinical range.”

ABAS-GAC, Adaptive Behavior Assessment System-Global Adaptive Composite; CBCL, Child Behavior Checklist; CC, community controls; CI, confidence interval; DAS, Dyadic Adjustment Scale; FAD, Family Assessment Device; OI, orthopedic injuries; PSI-PD, Parenting stress index-parental distress; PSI-PCDI, Parenting stress index-Parent Child Dysfunction Interaction; SD, standard deviation.

Finally, cognitive measures and PCS ratings were obtained 6-month post-injury for the OI, and immediately after recruitment for the CC (Table 4). As expected, neither group reported elevated post-concussive symptoms and no group differences were found, whether in the last week or the past 6 months. When the OI and CC were compared in terms of their cognitive performance, they did not differ in terms of general intellectual functioning, verbal abilities, executive functions, or theory of mind.

Table 4.

Post-concussive and Cognitive Outcomes

	OI	CC
	M (SD)	M (SD)	Difference	95% CI	t	p	d
Post-concussive symptoms
PCS-I—last week	0.67 (1.08)	0.69 (1.28)	−0.02	−0.42 to 0.38	−0.10	0.92	0.02
PCS-I—last 6 months	0.95 (1.59)	0.63 (1.53)	0.32	−0.21 to 0.85	1.21	0.23	0.21
Global cognition
Intellectual functioning (percentile)	59.53 (23.61)	60.68 (24.79)	−1.15	−9.27 to 6.98	−0.28	0.78	0.05
Verbal abilities (percentile)	55.88 (27.07)	56.00 (25.73)	−0.12	−9.02 to 8.77	−0.03	0.98	0.00
Theory of mind
False belief task	0.76 (0.74)	0.85 (0.73)	−0.09	−0.36 to 0.17	−0.70	0.49	0.13
Desires task	5.30 (0.97)	5.45 (0.85)	−1.15	−0.52 to 0.23	−0.78	0.44	0.17
Discrepant desires task	2.17 (1.62)	2.14 (1.46)	0.02	−0.97 to 1.02	0.05	0.96	0.02
Executive functioning
Tower of Hanoi	2.25 (1.88)	2.10 (1.49)	0.15	−0.58 to 0.88	0.41	0.69	0.09
Delay of gratification	4.61 (3.09)	4.81 (2.85)	−0.20	−1.23 to 0.82	−0.39	0.70	0.07
Spin the pots	0.70 (0.21)	0.71 (0.18)	−0.02	−0.08 to 0.05	−0.50	0.62	0.09
Conflict scale	28.93 (17.07)	30.89 (16.11)	−1.94	−7.74 to 3.86	−0.66	0.51	0.12
Shape stroop	2.45 (0.98)	2.57 (0.77)	−0.13	−0.42 to 0.17	−0.85	0.40	0.15

CC, community controls; CI, confidence interval; OI, orthopedic injuries; PCS-I, Post-concussive Symptom Interview; SD, standard deviation.

Discussion

The aim of this study was to directly compare CC (or “typically developing”) and OI controls aged between 18 and 60 months on a range of variables relevant to early development and to pediatric TBI research. Contrary to the formulated hypothesis, the two groups did not differ on any variable tested, indicating similar demographic profiles (age, education, SES, gender, language, ethnicity, handedness), development (birth weight, Apgar, age at first words and first steps), medical history (pregnancy characteristics, birth disorders, medical problems, medication), behavior (internalizing and externalizing problems), adaptive functioning, family factors (family functioning, parental stress, relationship adjustment), concussion-like symptoms (PCS-I), cognition (IQ, verbal abilities, executive functioning), and social cognition (theory of mind). The results align with those of Mathias and colleagues who also compared these two types of control groups in a sample of adults between 18 and 79 years and found similarities between them across demographic (age, education, SES, gender), medical (medication use, medical diagnoses), psychosocial (fatigue, pain, depression, social support, concussion-like symptoms, community integration), and cognitive (IQ, motor and information processing speed, memory, verbal fluency, test effort) factors.¹ To our knowledge, the current study is the first to compare these control groups on pre-morbid functioning ratings and to conduct comparisons directly between OI and CC in children. Despite the numerous comparisons, no statistically significant group difference was found, and between-group effect sizes were small across all measures. Only pre-injury and post-injury measures of conceptual adaptive behavior (ABAS), which refers to communication, functional academics, and self-direction skills, approached statistical significance. Taken together, our results suggest no meaningful differences between OI and CC groups in a group of children aged between 18 and 60 months.

The findings of the current study further call into question the putative advantages of orthopedic versus community control groups. Because this study included some pre-injury questionnaires in the OI group, it is novel in suggesting that, contrary to the stated higher pre-morbid risk factors for sustaining injury in the OI group,^11,18,19 CC and OI start off with similar behavioral and adaptive functioning and do not differ on a range of demographic and developmental indicators that have potential relevance to the study of pediatric TBI. The data also suggest that despite experiencing trauma-related medical consultation and follow-up, the two groups do not differ on symptom outcome, behavior, adaptive functioning, family functioning, cognition, or social cognition 6 months after the orthopedic injury. Given the comparability of OI and CC, future TBI research could benefit from important cost savings and ease of recruitment by using CC. Nevertheless, our understanding of injury mechanisms is still in its early stages and recent work suggests that concomitant peripheral injuries can modify the outcomes and the pathobiology of TBI.⁵⁴ A comparison group of orthopedically injured individuals might help to control for these mechanisms that are not well understood at the moment.

Despite supporting the findings of Mathias and colleagues in adults, the results of this study should be construed in light of the particularities of the developmental period studied and caution should be exercised in generalizing the comparability of the two control groups to older pediatric stages.¹ Our sample consisted of preschoolers, aged between 18 and 60 months and, as the youngest members of society, preschoolers present the shortest developmental histories. As such little is known of their exact cognitive, social, and behavioral make-up. Children with known developmental, psychological, neurological, or other medical pathophysiology were excluded from the study, but it is possible that some individuals will go on to develop or be diagnosed with conditions (e.g., attention deficit hyperactivity disorder, learning disabilities, language delay) at older ages and this may later affect the comparability of the two groups. Moreover, there is evidence that children with developmental disability are more likely to sustain injury.⁵⁵ Future studies in older children and adolescents should verify whether the findings of this study extend upward through development and should carefully monitor the occurrence of developmental disabilities in populations of interest.

The data should also be interpreted alongside study limitations. Although the outcomes assessed are numerous and present a wide range of domains of functioning, they are limited to those included in the larger prospective study, and as such do not constitute a complete neuropsychological or psychosocial assessment. In addition, outcome was only evaluated at 6-months post-injury (for the OI group) and therefore the findings do not preclude the possibility that the two groups may have differed on outcome at more acute stages given the possible impact of pain, fatigue, post-traumatic stress, and other medical interventions in the OI group in the shorter term (acute–3 months). Attention, processing speed, reaction time, perceptual skills, and motor abilities may all be relevant to pediatric TBI populations and functioning in these domains should be compared in future studies. Given the young age of the participants, other individual and family variables may also be of interest, such as child temperament and parent psychological factors (e.g., anxiety and depression) in their parents. Finally, the participants in the study were compared on a measure of post-concussive symptoms given the high relevance of such a measure to studies of mTBI; however, there is currently no validated PCS questionnaire for infants, toddlers, or preschoolers. In the absence of any age-appropriate measure, the PCS-I was used,⁴¹ (validated for youth 5 to 18 years of age). Future work developing and applying more developmentally appropriate scales of PCS in young children may reveal alternate findings.

Conclusion

Preschool children (i.e., 18–60 months of age) with OI present with demographic, developmental, medical, and pre-morbid behavioral and adaptive profiles comparable to those of control children recruited from community settings. They are also comparable on measures of adaptive functioning, behavior, family functioning, concussive-like symptoms, global cognition, executive functioning, and social cognition (theory of mind) when tested 6 months after injury. The findings are applicable to studies seeking to identify appropriate control groups in the context of pediatric TBI research and suggest no clear advantage of community versus injured controls in the youngest developmental age group, although further work should verify this conclusion in other domains of functioning, at more acute assessment time-points, and in older children. Also, the true comparability of the two control groups should be tested with respect to clinical groups of children with TBI across the range of severities and with respect to other cognitive outcome variables relevant to TBI research, such as attention, reaction time, and working memory.

Footnotes

Acknowledgments

This study was supported by the Canadian Institutes of Health Research (MOP11036 to M.H.B). Thank you to the LION study members and the ED team for their collaborative efforts.

Author Disclosure Statement

No competing financial interests exist.

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