Long-Term Participation after Mild Traumatic Brain Injury in Comparison to Orthopedic Trauma Controls: Results from a Longitudinal Multicenter Observational Cohort Study

Abstract

A subgroup of patients shows incomplete recovery after mild traumatic brain injury (mTBI). Outcomes are commonly measured on the level of symptoms or functional recovery. An alternative way to study outcome after mTBI is to measure the level of participation. The objectives of this study were to examine (1) the level of participation in patients with mTBI at 12 months post-injury in comparison to a non-head injury orthopedic trauma control group; (2) the relationship between the outcome domains participation, functional outcome, and post-concussion symptoms. A prospective, longitudinal, multicenter cohort study was conducted. Participants were 140 adults with mTBI and 144 adults with minor (non-head) orthopedic injury. The following outcomes were measured: participation (Utrecht Scale for Evaluation and Rehabilitation-Participation: USER-P), functional outcome (Glasgow Outcome Scale Extended: (GOS-E), and post-concussion symptoms (Rivermead Post-Concussion Symptoms Questionnaire: RPQ). Adults with mTBI have a significantly lower objective participation level (USER-P Frequency scale) than controls. No differences were found between the groups on subjective participation (USER-P Restrictions and Satisfaction scales) nor on functional outcome (GOS-E). Fifty-three people with mTBI (38%) had a score of ≥2 on ≥3 items, while 26 (19%) had an unfavorable USER-P outcome (≥2 restrictions) and only 9 (6.5%) had an unfavorable GOS-E score (<7). In both groups, the presence of persistent symptoms led to a significantly unfavorable outcome on both the USER-P and GOS-E. Participation frequency is lower in mTBI than in orthopedic controls, mainly determined by a significantly lower number of hours of (un)paid work, education, and/or household activities. People with mTBI more often report post-concussion symptoms, but functional recovery is not different between the groups. Participation seems to better represent incomplete recovery than functional outcome, but future research should confirm these findings.

Introduction

Mild traumatic brain injury (mTBI) is a highly prevalent global health issue, with an estimated worldwide incidence of 600 per 100,000.¹ It is typically defined by a Glasgow Coma Scale (GCS) score of 13 to 15 following an acute head injury resulting from an external force or blow to the head.² mTBI may lead to negative consequences in the (sub)acute phase such as headaches, dizziness, sleep disturbances, cognitive problems (i.e., slowed processing speed, attention and memory difficulties), and affective disturbances (i.e., irritability, emotional lability), which are typically expected to recover within the first 3 months after injury.³

Although the overall prognosis appears positive, a subgroup of patients shows incomplete recovery. However, in the field of mTBI research, there was no consensus about the definition of incomplete recovery, which in turn led to a lack of agreement in assessment and outcomes.⁴

Many studies investigating outcomes after mTBI focus on post-concussion symptoms (i.e., headache, fatigue, cognitive complaints, or emotional disturbances). These studies mostly use the Rivermead Post-Concussion Symptoms Questionnaire (RPQ) to measure the frequency and level of post-concussion symptoms.⁴ However, this approach comes with some difficulties. First, the frequency and level of post-concussion symptoms varies across studies due to methodological differences.^5,6 Secondly, these symptoms are not specific to mTBI but are also prevalent after other (non-head related) injuries,⁷ including whiplash injury to the neck,⁸ chronic pain,⁹ and in the general population.¹⁰ Therefore, it is stated that the results of post-concussion symptom questionnaires as outcome measures following mTBI should be interpreted with caution.⁷

Many other studies investigating outcomes after mTBI focus on functional recovery, commonly measured with the Glasgow Outcome Scale Extended (GOS-E) (see, for instance references^4,11

–14). These studies show that around 20–50% of patients with mTBI have incomplete functional recovery 1 year post-injury (percentages differ according to the cut-off values applied). The usefulness of the GOS-E as an outcome measure in patients with mTBI has also been disputed.^4,11 The GOS-E is a global measure (an 8-point scale, ranging from death [1] to complete recovery [8]) and therefore may not be sufficiently sensitive to capture different health and participation problems despite good overall functioning.^4,11

Moreover, there may be a difference between outcomes measured on the level of symptoms versus functional outcome. For example, in Karr et al. (2020)¹⁵ complicated mTBI, uncomplicated mTBI, and head injury patients differed in functional outcome but not on symptom level. Whereas a substantial subgroup of patients continues to experience at least one post-concussion symptom up to 1 year post-injury, most people (70–80%) show full functional recovery in terms of resuming work and study activities at pre-injury level.^13,16

An alternative way to study outcome after mTBI is to measure the level of participation. According to the International Classification of Functioning, Disability and Health (ICF) (World Health Organization), participation can be defined as “the person’s involvement in a life situation,” including daily activities as well as social roles. The concept encompasses domains such as mobility, domestic life, interpersonal interactions and relationships, as well as community, social, and civic life. Participation is an important outcome domain after injury or disease, and improvements at the level of participation are the primary goal in rehabilitation treatment.¹⁷

Participation can be measured in many different ways. For instance, one can focus on different life domains (i.e., self-care, work), measure different aspects (i.e., capacity, satisfaction), use different methods (i.e., Likert scales, statements), and ask different responders (i.e., patient, clinician). A comprehensive and multifactorial measure of participation may capture all of these aspects. The GOS-E measures aspects of participation (e.g., changes in work situation due to the mTBI) but in a more global way. In addition., there are mTBI outcome studies that focus primarily on return to work (RTW),^18,19 but that is just one aspect of participation. Participation has been studied after moderate to severe traumatic brain injury,^20,21 and these studies show improvement during the first year post-injury. However, for most patients, participation levels do not reach pre-injury levels. Renaud et al. (2020)²² investigated participation after mTBI in children and adolescents and found that between 38% (self-report) and 67% (parents’ perspective) returned to premorbid levels of participation at 6 months post-injury.

The first aim of the present study was to examine the level of participation by using a comprehensive measure (objective frequency of participation, subjective restrictions, and satisfaction with participation) in patients with mTBI at 12 months post-injury and compare this with the level of participation at 12 months of persons that had a traumatic non-head-related orthopedic injury (hereafter referred to as controls). As participation may be a more comprehensive outcome variable than functional recovery, extrapolating the results of the TRACK-TBI study, we anticipated to find participation problems in more than 22% of the patients with mTBI, which was the percentage of patients with an unfavorable outcome on the GOS-E (score <7).¹² In line with the TRACK-TBI study, we also expected to find more participation problems in patients with mTBI than in orthopedic controls.

The second aim of this study was to examine the relationship between the different outcome variables of importance after mTBI, namely participation, functional outcome, and post-concussion symptoms. This way we gain insight into the additional value of participation as an outcome domain after mTBI. We expected that there would be patients that perform well in terms of overall functional outcome (GOS-E) but do have specific participation problems. As persistent symptoms are associated with reduced return to work levels, we hypothesized that the presence of three or more symptoms at 12 months post-injury would be associated with lower levels of participation and functional outcome.

Materials and Methods

For this prospective, longitudinal, multicenter cohort study, ethical approval was received from the medical ethics committee of Maastricht University and Maastricht University Medical Centre (METC 16-4-209). Data used for the current study was collected as part of a larger data collection effort investigating outcomes after mTBI. In the cohort study there were four measurement points post-traumatic injury, namely within the second week at the participant’s home and after respectively 3 months, 6 months, and 12 months, at which participants were asked to complete questionnaires (online or assisted at their own home upon request). Data obtained at 2 weeks (baseline characteristics and injury-related variables) and at 12 months (primary outcome variables) after injury were analyzed in the current study.

Participants

Participants were adults who had an mTBI (mTBI group) and adults who had a minor orthopedic injury in at least one extremity (control group). This control group was chosen because they also suffered a minor trauma for which they visited the ED of the hospital. As this may influence the level of distress people experience, we aimed to keep this comparable in both groups. Moreover, post-concussion symptoms are not specific to mTBI. Patients for both groups were recruited from March 2017 to August 2019 at the emergency departments (ED) at six participating hospitals in the Netherlands (Laurentius Ziekenhuis Roermond, Maastricht UMC+, St. Jans Gasthuis Weert, VieCuri Medisch Centrum Venlo, and Zuyderland Heerlen/Sittard). Follow-up measures took place until August 2020.

The following inclusion criteria were used for the mTBI group: diagnosed with mTBI by their treating health care professional (either emergency room physician or neurologist) using the following criteria at the emergency department: a history of impact to the head, a GCS score between 13 and 15 at 30 min after the impact or later at hospital admission, and in case of a GCS score of 15, at least one of the following: loss of consciousness (LOC) (≤30 min), posttraumatic amnesia (PTA) (≤24 h), other transient neurological signs such as vomiting; aged 18 years or older; fluent in Dutch; able and willing to provide informed consent. Exclusion criteria for the mTBI group were as follows: a history of neurological disease or injury such as TBI, stroke, epilepsy, and multiple sclerosis; a history of psychiatric disorders for which hospitalization was needed; being under the influence of illicit substances at the time of injury or a history of drug addiction; and use of psychoactive medication known for cognitive (side) effects. Earlier, mTBI and alcohol use were not exclusion criteria.

The inclusion and exclusion criteria for the control group were the same, except for a diagnosis of mTBI. Participants were instead required to have received a diagnosis of a minor orthopedic injury in the extremities (e.g., bone fracture or sprain) from a health care professional at the emergency department. In addition, the injury did not involve the head, and there were no LOC, PTA, or transient neurological signs.

Measures

Demographic and personal variables

A demographic questionnaire was used to collect information about age, gender, education, pre-injury alcohol use, and psychological treatment history. Education was categorized on an 8-point scale from no education to higher education. A higher education level includes completion of a college or university degree.

Injury-related variables

Injury-related variables including GCS score, LOC, PTA, hospital admission, brain scan abnormalities, alcohol use at the time of injury, cause of injury, and orthopedic injury type were retrieved from the hospital database. These variables were scored according to the procedures in each hospital and following the Dutch neurology guidelines for mild traumatic head/brain injury.

Participation

Participation was assessed using the Utrecht Scale for Evaluation and Rehabilitation-Participation (USER-P). The USER-P was used for its unique perspective in combining the objective as well as the subjective aspects of participation, and its strong psychometric foundations and because it covers the description of participation as proposed by the ICF model. The USER-P measures three aspects of participation: frequency of activities, experienced participation restrictions due to health condition, and satisfaction with participation.¹⁷ The Frequency scale measures the objective level of participation, while the Restrictions and Satisfaction scales offer insight into the subjective rating of participation. The Frequency scale consists of part A; (un)paid work, education, and/or household activities; and part B: sports, leisure activities, and social contact. It is a valid and reliable measure in patients with brain injury of different etiologies and injury severity levels with a good internal consistency (Cronbach α = 0.70–0.91).¹⁷ It consists of 31 items across the three scales. Each sumscore of a scale is converted into a score ranging from 0 to 100. Higher scores indicate good levels of participation (higher frequency of activities, less restrictions, and higher satisfaction). At the first assessment there were Frequency scale questions asking about premorbid levels of participation. All scales used at 12 months assessed the situation at that moment. An unfavorable outcome is defined by two or more restrictions (activity labeled as “not possible, with assistance, or with difficulty”) on the restrictions scale (similar to^23,24).

Functional outcome

Functional outcome was assessed with the GOS-E,²⁵ which measures functional outcome on an eight-point scale (8 = upper good recovery, 7 = lower good recovery, 6 = upper moderate disability, 5 = lower moderate disability, 4 = upper severe disability, 3 = lower severe disability, 2 = vegetative state, and 1 = death). The GOS-E is a reliable measure in patients with TBI.²⁶ We used the official Dutch translation of the CENTER-TBI. A GOS-E score of ≥7 (good recovery), indicating a return to full functional status at work and in daily activity, was used as a cut-off value for favorable outcome.^12,27

Post-concussion symptoms

The level and severity of post-concussion symptoms were assessed with the RPQ.²⁸ It is a valid and reliable measure in mTBI^29,30 measuring the severity of symptoms in the past 24 h in comparison with pre-injury levels (questions are stated as “compared to before the accident, do you suffer now from…”). It consists of 16 items, rated on a five-point Likert scale ranging from “not experienced at all” to “a severe problem.” The total score ranges from 0 to 64, with a higher score indicating more severe symptoms.

Procedure

Following diagnosis of mTBI or orthopedic injury, the health care professional at the ED checked in- and exclusion criteria, asked whether the patient’s contact details could be forwarded to the researchers, and gave potential participants information about the study. The researcher contacted the patient within one to five working days via telephone, and after a patient expressed interest in the study, a first measurement was scheduled within 2 weeks after the injury (T1). This could take place at the participant’s home or a different location (i.e., university). At this meeting, the informed consent was signed, after which the questionnaires were completed in an online testing environment. The researcher could provide help to navigate this online system. In addition, the researcher checked whether the participants followed the instructions given for each questionnaire to make sure that the questions and items were interpreted correctly. After completing the first measurement, participants received a notification by e-mail for the upcoming follow-ups: after 3 months (T2), 6 months (T3), and 12 months (T4). Participants were given 4 weeks to fill in the questionnaires online independently (if necessary, they received a reminder after 2 weeks).

Statistical analyses

Participants with missing data on the USER-P at the 12-month assessment were excluded from analysis in this study. The included versus excluded participants were compared on baseline characteristics to assess the representativeness of the sample using parametric (independent samples t-test) and non-parametric (Χ ²-test, Mann–Whitney U test) tests when appropriate.

Baseline and injury-related characteristics were compared between the mTBI and orthopedic control groups, using parametric (independent samples t-test) and non-parametric (chi-square test, Mann–Whitney U test) testing when appropriate. In case baseline differences between the groups were present, these were corrected for in subsequent analyses of comparison.

USER-P, GOS-E, and RPQ scores for patients with mTBI at 12 months post-injury were described and compared to the orthopedic control group using independent samples t-tests. Chi-square tests were conducted to assess the difference in unfavorable/favorable outcome between the groups. For the USER-P frequency scores, a one-way ANCOVA was conducted to control for baseline differences between the mTBI and orthopedic control groups. For the mTBI group, correlations were calculated between the conventional severity measures (GCS, LOC, PTA, brain abnormalities, and hospital admission) and the outcome variables using Spearman or Pearson’s correlation coefficients or one-way ANOVA where appropriate.

In order to assess the relationship between participation and functional outcome, we compared the number of participants with an unfavorable outcome on either the USER-P or GOS-E and an unfavorable outcome on both.

In order to assess the relationship between post-concussion symptoms, participation, and functional outcome, independent samples t-tests (for USER-P scale total scores and GOS-E total score) and Chi-square tests (for unfavorable USER-P/GOS-E outcome) were conducted to assess the difference between mTBI participants with three or more versus those with two or less post-concussion symptoms.

The data were analyzed using IBM SPSS Statistics for Windows, Version 26.0 (Armonk, NY: IBM Corp). For all analyses, assumptions were checked. Results of statistical tests were considered significant if p ≤ 0.05.

Results

Participant characteristics

In total, 186 participants with mTBI and 181 control participants signed informed consent. Due to incomplete USER-P data at 12 months, 46 mTBI, and 37 control participants were excluded from further analysis. The analyses were performed with 140 mTBI and 144 control participants. At baseline, included mTBI participants were significantly older (t[184] = 2.60, p = 0.010) and less likely to be receiving current psychological treatment (X² [1] = 7.06, p = 0.008) compared with the excluded mTBI participants (see Supplementary Table S1). There were no significant differences between included and excluded control participants.

Characteristics of included participants are displayed in Table 1. The mTBI group was significantly older (t[269] = 2.04, p = 0.043), more often male (X² [1] = 8.90, p = 0.003), and more often hospitalized (X² [2] = 30.91, p < 0.001) than the control group. The mTBI group had significantly lower premorbid USER-P Frequency total scores (t[282] = −2.30, p = 0.022) and premorbid USER-P Frequency part A scores than the control group.

Table 1.

Demographics and Injury Related Characteristics of the mTBI (n = 140) and Control (n = 144) Groups

Characteristics	mTBI (n = 140)	CG (n = 144)	p value
Age at injury, mean (SD), range	50.7 (17), 18–76	46.9 (14), 18–66	0.043*
Sex, n (%)			0.003*
Male	86 (61.4)	63 (43.8)
Female	54 (38.6)	81 (56.3)
Higher education level^a, n (%)	53 (37.9)	48 (33.3)	0.774
Current psychological treatment, n (%)	4 (2,9)	7 (4.9)	0.429
History of psychological treatment, n (%)	17 (12.1)	24 (16.7)	0.278
Premorbid USER-P Frequency
Total score	31.7 (10.0)	34.5 (8.7)	0.011*
Part A (work, study, domestic chores)	30.0 (12.3)	33.23 (11.4)	0.022*
Part B (sports, leisure activities, social contact)	33.7 (11.3)	35.8 (10.6)	0.061
Hospital admission, n (%)	33 (23.6)	3 (2.1)	<0.001*
Brain scan abnormalities, n (%)	18 (12.9)
GCS score, n (%)
13	4 (2.9)
14	17 (12.1)
15	119 (85.0)
Loss of consciousness (min) (n = 125)
n (%)	89 (71.2)
Duration, mean (SD), range	3.5 (5.5), 0.5–29.0
Posttraumatic amnesia (hours) (n = 132)
n (%)	92 (69.7)
Duration, mean (SD), range	1.9 (4.3), 0.0–23.0
Pre-injury alcohol use, n (%)			0.496
Never	18 (12.9)	18 (12.5)
Monthly or less	29 (20.7)	34 (23.6)
2–4 times per month	36 (25.7)	46 (31.9)
2–3 time per week	34 (24.5)	31 (21.5)
4 or more times per week	23 (16.4)	15 (10.4)
Alcohol use at the time of injury, n (%)	(n = 123)	(n = 5)	^b
Yes, but no intoxication	14 (11.4)	1
Yes, and intoxication	23 (18.7)	2
Cause of injury, n (%)
Falls	55 (39.3)	60 (41.7)	<0.001*
Traffic	64 (45.7)	27 (18.8)
Violence	4 (2.9)	1 (0.7)
Sport	14 (10.0)	40 (27.8)
Struck by object	1 (0.7)	15 (10.4)
Other	2 (1.4)	1 (0.7)
Orthopedic injury type, n (%) (n = 139)
Fracture		104 (72.2)
Contusion		8 (5.6)
Sprain/strain		20 (13.9)
Luxation/dislocation		7 (4.9)
Other		4 (2.8)

Higher education level includes completion of a college or university degree.

Not tested because of small n in CG.

Baseline characteristics measured at 2 weeks/ in the second week post-injury (for USER-P Frequency part A questions are adapted to ask about premorbid levels).

mTBI, mild traumatic brain injury; CG, control group; GCS, Glasgow Coma Scale; LOC, Loss of consciousness; PTA, Post traumatic amnesia; USER-P, Utrecht Scale for Evaluation and Rehabilitation-Participation.

Correlations between the mTBI severity measures and the outcome measures are shown in Table 2, and revealed a small but significant correlation between GCS and USER-P Satisfaction (rho = −0.208) and GOSE-E (rho = −0.199).

Table 2.

Correlations between Injury Severity Measures and Outcome Measures

	USER-P frequency	USER-P restrictions	USER-P satisfaction	GOS-E	RPQ
GCS (Spearman correlation)	−0.129	−0.105	−0.208*	−0.199*	0.081
PTA, h (Pearson correlation)	−0.032	0.020	0.073	0.035	0.004
LOC, min (Pearson correlation)	0.111	0.066	0.097	0.150	−0.103
Neuroimaging abnormalities (CT or MRI) (p value for one-way ANOVA)	0.327	0.172	0.441	0.304	0.229
Hospital admission (p-value for one-way ANOVA)	0.689	0.439	0.363	0.600	0.676

Participation, functional outcome, and post-concussion symptoms at 12 months post-injury

At 12 months post-injury, mTBI participants had a USER-P Frequency scale total score of 36.2 (part A score of 27.7 and part B score of 44.8), a USER-P Restrictions scale score of 95.6, and a USER-P Satisfaction scale score of 78.6 (see Table 3).

Table 3.

Outcome at 12 Months Post-Injury

Outcome	mTBI (n = 140)	CG (n = 144)	p value
USER-P, mean (SD)
Frequency
Total score	36.2 (10.4)	40.5 (8.9)	<0.001*
Part A (work, study, domestic chores)	27.7 (12.0)	35.7 (31.5)	0.006*
Part B (sports, leisure activities, social contact)	44.8 (15.5)	48.0 (15.0)	0.077
Restrictions	95.6 (11.2)	96.0 (11.8)	0.740
Satisfaction	78.6 (16.6)	81.2 (13.7)	0.144
Unfavorable outcome (≥2 restrictions)^a n (%)	26 (18.6)	20 (13.9)	0.356
GOS-E	(n = 138)
Total score, median	8.0	8.0	0.165
Unfavorable outcome (<7)^b n (%)	9 (6.5)	11 (7.6)	0.715
RPQ
Total score, mean (SD)	9.5 (10.9)	4.9 (10.1)	<0.001*

*Significant at p < .05.

Two or more restrictions (activity labeled as “not possible, with assistance, or with difficulty”) on Restriction scale.

GOS-E total score < 7.

mTBI, mild traumatic brain injury; CG, control group; USER-P, Utrecht Scale for Evaluation and Rehabilitation-Participation; GOS-E, Glasgow Outcome Scale—Extended; RPQ, Rivermead Post-Concussion Symptoms Questionnaire.

Compared to the orthopedic control group, the mTBI group scored significantly lower on the USER-P Frequency scale total score (t[273] = −3.68, p < 0.001) and USER-P Frequency scale part A (t[282] = −2.80, p = 0.006). On an item level, mTBI participants scored significantly lower on the Frequency scale items: “paid work” (t[266] = −3.03, p = 0.003), “going out” (t[279] = −3.70, p = 0.000), “visiting family or friends” (t[272] = −2.32, p = 0.021), and “being visited by family or friends” (t[282] = −2.52, p = 0.012). While correcting for baseline differences between the groups (age, gender, hospitalization, premorbid USER-P Frequency scores) mTBI participants still showed significantly lower USER-P Frequency scale total scores at 12 months compared to controls (F[1] = 7.03, p = 0.008; adjusted M mTBI 37.0; adjusted M orthopedic controls 40.0).For the USER-P Frequency scale part A, correcting for baseline differences, the mTBI group still has significantly lower scores compared to orthopedic controls (F[1] = 5.13; p = 0.02; adjusted M for mTBI = 28.6 and for orthopedic controls 34.8).

There were no significant differences between the groups on the USER-P Frequency scale part B (t[282] = −1.78, p = 0.077), or USER-P Restrictions scale (t[282] = −.33, p = 0.740), USER-P Satisfaction scale (t[282] = −1.47, p = 0.144), and remain not significant after correcting for baseline differences (p > 0.05). The level of unfavorable outcome on the USER-P was also not significantly different between the groups (X² [1] = 0.85, p = 0.356).

At 12 months post-injury, no significant differences were found between the mTBI participants and orthopedic controls on the GOS-E on both the median total score (z = −1.387, p = 0.165) and (un)favorable outcome (X² [1] = 0.13, p = 0.715) (see Table 3). This remains the same after correcting for baseline differences (F[1] = 0.32; p = 0.57). In addition, at 12 months post-injury, mTBI participants had significantly more post-concussion symptoms (RPQ total score) (t[279] = 3.62, p = 0.001) than orthopedic controls (see Table 2). That is still true when adjusted for baseline differences (F[1]=16.8; p = < 0.001; adjusted M for mTBI = 9.8 and for orthopedic controls = 4.6). Looking at the most reported symptoms on the RPQ, the top 5 for patents with mTBI was fatigue, forgetfulness, concentration problems, sleep problems, and mental slowness (i.e., taking longer to think), while for the orthopedic controls this were fatigue, sleep problems, feeling frustrated, concentration problems, and feeling depressed.

Relationship between participation and functional outcome

The number of participants with unfavorable outcomes (USER-P, GOS-E, or both) is displayed in Table 4. In the mTBI group, 26 participants (18.6%) had an unfavorable outcome on the USER-P, but only 9 participants (6.5%) had an unfavorable outcome on the GOS-E. In the orthopedic control group, 20 participants (14%) had an unfavorable outcome on the USER-P, but only 11 participants (7.6%) had an unfavorable outcome for the GOS-E. In both the mTBI and orthopedic control groups, only 4 participants (around 3%) had an unfavorable outcome on both the USER-P and GOS-E.

Table 4.

Number of Participants with Unfavorable USER-P, GOS-E, and Both

Unfavorable outcome	mTBI (n = 140)	CG (n = 144)
Unfavorable USER-P^a, n (%)	26 (18.6)	20 (13.9)
Unfavorable GOS-E^b, in (%)	(n = 138)
Unfavorable GOS-E^b, in (%)	9 (6.5)	11 (7.6)
Unfavorable USER-P and GOS-E, n (%)	4 (2.9)	4 (2.8)

Two or more restrictions (activity labeled as “not possible, with assistance, or with difficulty”) on Restriction scale.

GOS-E total score < 7.

mTBI, mild traumatic brain injury; CG, control group; USER-P, Utrecht Scale for Evaluation and Rehabilitation-Participation; GOS-E, Glasgow Outcome Scale—Extended.

Relationship between participation and post-concussion symptoms

mTBI participants with 3 or more symptoms at 12 months post-injury had significantly lower USER-P Frequency, Restrictions, and Satisfaction scores (t[138] = 3.12, p = 0.002; t[57] = 3.86, p < 0.001; t[80] = 4.88, p < 0.001), had a more unfavorable USER-P outcome (X² [1] = 26.3, p < 0.001), a lower GOS-E median total score (z = −3.730, p < 0.001), and a more unfavorable GOS-E outcome (X² [1] = 14.4, p < 0.001) (see Table 5) compared with mTBI participants with 2 or less symptoms at 12 months post-injury.

Table 5.

Comparison Participants With and Without Post-Concussion Symptoms

	mTBI with 3 or more symptoms^a (n = 53)	mTBI with 2 or less symptoms (n = 87)	p value	CG with 3 or more symptoms (n = 31)	CG with 2 or less symptoms (n = 112)	p value
USER-P
Frequency mean (SD)	32.8 (11.2)	38.3 (9.4)	0.002*	36.5 (9.6)	41.6 (8.5)	0.005*
Restrictions mean (SD)	90.2 (16.1)	98.8 (4.3)	0.000*	89.7 (14.9)	98.4 (7.3)	0.003*
Satisfaction mean (SD)	69.8 (18.8)	84.0 (12.5)	0.000*	70.7 (11.8)	84.5 (12.4)	<0.001*
Unfavorable outcome (≥2 restrictions)^a n (%)	21 (39.6)	5 (5.74)	0.000*	17 (54.8)	9 (8.0)	<0.001*
GOS-E^b	(n = 51)			(n = 30)
Total score median	7.0	8.0	0.000*	7.0	8.0	0.002*
Unfavorable outcome (<7)^b n (%)	5 (9.8)	4 (4.6)	0.0000*	2 (6.7)	8 (7.1)	0.001*

*Significant at p < .05.

3 of more symptoms indicated as problem (score 2 or higher) on the RPQ ^abTwo or more restrictions (activity labeled as ‘not possible, with assistance, or with difficulty’) on Restriction scale.

GOS-E total score.

mTBI, mild traumatic brain injury; CG, control group; USER-P, Utrecht Scale for Evaluation and Rehabilitation-Participation; GOS-E, Glasgow Outcome Scale—Extended.

In the orthopedic control group participants with 3 or more symptoms at 12 months post-injury had significantly lower USER-P Frequency, Restrictions and Satisfaction scores (t[141] = 2.85, p = 0.005; t[34] = 3.14, p = 0.003; t[141] = 5.54, p < 0.001), had more unfavorable USER-P outcome (X² [2] = 39.3, p < 0.001), a lower GOS-E median total score (z = −3.052, p = 0.002), and more unfavorable GOS-E outcome (X² [2] = 13.0, p = 0.001) (see Table 5) compared with orthopedic control participants with two or less symptoms at 12 months post-injury. There were no significant differences in the GOS-E total score (t[141] = 1.71, p = 0.09).

Discussion

In this prospective, longitudinal, multicenter cohort study, we examined outcome, in terms of participation, in patients with mTBI at 12 months post-injury in comparison to orthopedic trauma controls. We found that adults with mTBI had a significantly lower objective participation (i.e., frequency), determined by significantly lower number of hours of (un)paid work, education, and/or household activities, than orthopedic trauma controls. This difference remained significant after controlling for the lower premorbid level of participation in the mTBI group. There were no significant differences between patients with mTBI and controls on the more ‘subjective’ participation measures (USER-P Restrictions, and Satisfaction scales).

The mTBI and orthopedic trauma controls did not differ in functional outcome. More patients with mTBI were classified as having an unfavorable outcome in participation (19%) than in functional recovery (6.5%). On the symptom level, we found that patients with mTBI reported significantly more post-concussion symptoms than orthopedic controls. Patients with three or more symptoms after mTBI had a significantly lower level of objective and subjective participation and a lower level of functional outcome than patients with two or less symptoms. However, this is not specific to mTBI because the same results were found for orthopedic trauma controls. Moreover, participation seems to be more sensitive to symptom persistence than functional recovery, because in the subgroup of patients with mTBI with three or more symptoms, 10% scored unfavorable on the GOS-E, whereas 40% scored unfavorable on the USER-P. The same results were found in the control group, such that in the subgroup of orthopedic patients with symptoms, 55% scored unfavorable on the USER-P, whereas only 6.5% scored unfavorable on the GOS-E.

Earlier studies did examine return to work after mTBI as one of the elements of participation. Our finding that adults with mTBI had significantly lower objective participation (i.e., number of hours on paid work) than orthopedic controls 12 months post-injury is in line with the literature on reduced RTW after mTBI.^18,19 However, in the TRACK-TBI study, work problems (measured with the GOS-E) were equally prevalent in mTBI and orthopedic trauma patients.¹⁴ This may be due to the fact that the GOS-E measures work problems more globally than the USER-P, which specifies the number of working hours more precisely.

The finding that there were no differences between the mTBI and orthopedic control group on participation restrictions and satisfaction with participation may suggest that other factors than brain injury are crucial for the more subjective evaluation of participation. This is in line with the literature suggesting that after traumatic injury (both mTBI and orthopedic injuries), psychological factors (including pre-injury mental health, post-injury emotional distress, and maladaptive coping) and social factors, instead of injury-related variables (i.e., injury severity), have been shown to be the most important prognostic factors for recovery.^11,13,31,32

We did not find significant differences between mTBI and orthopedic controls on functional outcome measured with the GOS-E, which is contrary to previous research (i.e., the TRACK-TBI study) where at 12 months post-injury patients with mTBI scored lower on the GOS-E than orthopedic trauma controls. A possible explanation is that in the TRACK-TBI study the injury in the mTBI group may have been more severe because the percentage of patients with abnormalities on the CT-scan was much higher (45% vs. 13%) and the percentage of patients with a maximum GCS score was lower compared to the current study (71% vs. 85%).

Moreover, more patients with mTBI are classified as having an unfavorable outcome in participation than in functional outcome. This may indicate that the concept of participation represents incomplete recovery better than functional outcome. In the ICF model, functional outcome seems to reflect the level of activities and not participation, which is influenced more by personal and environmental factors.

However, caution is advised with this conclusion because studies use different cut-off points for unfavorable outcomes on the GOS-E. We used the cut-off of GOS-E total score <7 for unfavorable outcome (based on^12,27) and found 6% of patients with mTBI scoring unfavorably. For example, in the UPFRONT study¹³ and in the paper from Nelson et al., (2019) on the TRACK-TBI data,¹⁴ they used a GOS-E total score <8 for unfavorable outcome and found 44% and 53% (respectively) of patients with mTBI with unfavorable outcome. When using a cut-off value of GOS-E < 8 in our data, 45% of patients with mTBI (and 36% of the controls) had an unfavorable outcome. This lack of agreement on the definition of unfavorable outcome makes it difficult to compare study results and is a major problem in the mTBI literature.

The finding of more post-concussion symptoms in the mTBI group than orthopedic controls is in line with earlier studies (for example¹⁴). However, 22% of the orthopedic controls had three or more symptoms, which is in line with the literature (e.g.,⁷) stating that persistent symptoms are not specific for mTBI and can also be present without an injury to the head.

The finding that persistent symptoms—in both the mTBI and control groups—were associated with lower participation and functional outcome at 12 months post-injury is in line with previous research stating that a constellation of post-concussion symptoms interfere with resumption of work and other activities.¹⁹

The percentage of people with unfavorable outcomes on the GOS-E in our study is lower than in the TRACK-TBI study (i.e., our study had 6% GOS-E < 7 vs. 22–30% in the TRACK-TBI study; in our study, 45% had GOS-E < 8 vs. 53% in the TRACK-TBI sample).^12,14 This may be due to the fact that in the TRACK-TBI study they initially excluded patients with a GOS-E score of 8 at 6 months. However, the study soon expanded to include follow-up with all patients at 12 months, regardless of GOS-E score. In addition—as mentioned above—in the TRACK-TBI study, the injury may have been more severe because the percentage of patients with abnormalities on the CT-scan was much higher (45% vs. 13%) and the percentage of patients with a maximum GCS score was lower compared to the current study (71% vs. 85%).

Our study has some noticeable strengths. First, we had a reasonably large sample size. Secondly, we compared patients with mTBI to a relevant control group having experienced an acute mild incident for which the ED of a hospital was visited. By including a non-head injury orthopedic trauma control group, we gain insight into the importance of the involvement of the head for long-term participation after traumatic injury. Some limitations need to be mentioned as well. In both groups, outcome data at 12 months were missing. This may have influenced the results if, for instance, recovered patients were more likely to drop out. These missing data may have been the result of the COVID-19 pandemic that interfered with our follow-up data collection in the last half year. Lockdowns may have influenced participation levels. Furthermore, the unfavorable outcome on the USER-P was based only on the Restriction Scale, while the instrument was designed to measure the concept of participation on three scales, including both objective and subjective participation elements. Future research with other participation measures may shed more light on this issue. Secondly, we included patients who visited the ED, and therefore there is a bias of more severe mTBI, and the findings may not generalize to the broader mTBI population. This selection bias is, however, present in many mTBI cohort studies, which makes results incomparable to those studies where participants were recruited in the long term irrespective of initial presentation to health care. Additionally, eligible participants were recruited by clinicians at the ED. Clinicians follow Dutch guidelines for assessments of patients with mTBI at the ED (https://richtlijnendatabase.nl/richtlijn/licht_traumatisch_hoofd_hersenletsel_lth). However, we could not control how strictly these guidelines were followed by the participating EDs. The research team only received information on those patients that were informed by their clinician about the study. More people will have visited the ED who were not forwarded to the study, which may have induced a selection bias. Therefore, we cannot state how well our sample represents all patients with mTBI who visited the participating EDs during the recruitment period. However, the Dutch ethics guidelines do not permit the collection of data about people who do not enter the study; therefore, no information is available on non-recruited patients. Finally, we considered specific cut-offs for unfavorable outcomes and aligned the GOS-E to the USER-P by using two outcome categories as unfavorable (i.e., GOS-E <7 and USER-p ≥ 2 restrictions). We chose to apply a GOS-E <7 in this study because this gave us the opportunity to compare our findings to those of other large cohorts (such as TRACK-TBI).¹² However, other large cohort studies also applied the cut-off of GOS-E < 8 (such as the Upfront study).¹³ Future studies may also consider each deviation from complete recovery as unfavorable (i.e., GOS-E < 8 and USER-p ≥ 1 restrictions).

Clinical implications

We found that although the long-term prognosis for most patients with mTBI seems to be favorable, participation problems are prevalent in patients with mTBI with persistent symptoms. On the contrary, not all patients with symptoms have participation problems (around 40%). Asking about participation problems may be a valuable addition for referral to treatment or considering specific treatment opportunities.

Conclusions

Our study provides a first indication that measuring participation in a comprehensive way may be preferred as an outcome measure after mTBI. Future research should confirm these findings.

Transparency, Rigor, and Reproducibility Summary

This study was not formally registered. Data used for the current study were collected as part of a larger data collection effort investigating outcome after mTBI. Sample size of the larger study was 186 mTBI and 181 control participants. Due to incomplete data on the primary outcome measure of the current study (USER-P scores at 12 months post-injury), the analyses were performed with 140 mTBI and 144 control participants. A CONSORT diagram is not included because all available participants were entered in the analyses; included participants are compared to excluded ones. No power calculations were done separately for the current study, but sample size is sufficient for the chosen analyses. The analysis plan for the current study was not formally pre-registered, but the team member with primary responsibility for the analysis (principal investigator) certifies that the analysis plan was pre-specified. Blinding of participants was not relevant as it concerns a cohort study in which participants filled in on line questionnaires. Details on data acquisition and analyses are reported in the methods section. All equipment and software used to perform acquisition and analysis are widely available (e.g., SPSS). Key inclusion criteria and clinical outcomes are standard in the field. For all analyses assumptions were checked. No replication or external validation studies have been performed or are planned/ongoing at this time to our knowledge. Data and analytical code are available upon reasonable request to the principal investigator at Maastricht University (CvH). The publication will be available in an Open Access format.

Footnotes

Authors’ Contributions

J.M.: Conceptualization, formal analysis, writing—original draft; M.W.: Conceptualization, methodology, investigation, data curation, writing—review and editing; S.K.: Formal analysis, writing—review and editing; S.S.: Conceptualization, methodology, writing—review and editing; J.V.: Conceptualization, methodology, writing—review and editing; C.v.H.: Conceptualization, methodology, writing—review and editing, project administration, supervision.

Author’s Disclosure Statement

The authors have no competing financial interests exist.

Funding Information

No funding was received for this article.

Supplementary Material

Supplementary Table S1

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