Neuropsychologic function and level of caregiver supervision

221

The Relationship Between Neuropsychologic Function and
Level of Caregiver Supervision at 1 Year After Traumatic
Brain Injury
Tessa Hart, PhD, Scott Millis, PhD, Thomas Novack, PhD, Jeffrey Englander, MD,
Rebecca Fidler-Sheppard, BA, Kathleen R. Bell, MD
ABSTRACT. Hart T, Millis S, Novack T, Englander J, © 2003 by the American Congress of Rehabilitation Medi-
Fidler-Sheppard R, Bell KR. The relationship between cine and the American Academy of Physical Medicine and
neuropsychologic function and level of caregiver supervision at Rehabilitation
1 year after traumatic brain injury. Arch Phys Med Rehabil
2003;84:221-30.
Objectives: To evaluate distribution of levels of caregiver T90,000 persons BRAIN States, leavingdegreea of permanent
to
RAUMATIC
problem in the United
INJURY (TBI) is major health

per year with some
an estimated 80,000
supervision at 1 year after traumatic brain injury, and to deter-
mine neuropsychologic predictors of supervision level. disability relative to their preinjury status.1 TBI can alter role
Design: Prospective longitudinal design, concurrent mea- relationships, create marital disruption, and place great strain
surement of neuropsychologic function and supervision level. on the family system.2 Although persons of any age may be
Setting: Seventeen Traumatic Brain Injury Model Systems injured, TBI affects primarily young adults, bringing societal
centers. burden and personal hardship in the form of many years of lost
Participants: A total of 563 adults tested at 1 year postin- productivity. Of the multiple impairments caused by TBI, cogni-
jury; and a subgroup of 452 studied for neuropsychologic tive and behavioral deficits are more likely than physical limita-
function in the absence of impairment in mobility or basic tions to preclude successful return to work or other forms of social
self-care, as assessed by high FIM™ instrument motor scores. productivity.3 Caring for survivors with physical and cognitive
Interventions: Not applicable. disabilities places financial demands as well as less tangible bur-
Main Outcome Measure: Supervision level measured by dens on family members and government-funded institutions.
scores on Supervision Rating Scale (SRS). One important aspect of the caregiving role in relation to
Results: Two thirds (69%) of the sample was rated as moderate and severe TBI is the amount of supervision that is
independent of supervision. Participants without significant given to the injured person. Supervision implies the continuous
dysfunction on motor FIM were grouped into supervision or intermittent presence of another person to provide physical
groups differing in intensity of time commitment from care- care, instructions for or set-up of daily living tasks, problem
giver (independent, moderate supervision, heavy supervision). solving in case of emergency, or some combination of these.
In univariate analyses, groups differed on demographic vari- For adults who were functioning independently before their
ables (education, race, productivity prior to injury), duration of TBI, supervision means a major lifestyle change for both the
altered consciousness, and all but 1 neuropsychologic measure. person with TBI and the involved caregiver(s). Research sug-
A binomial regression model (complementary log-log model) gests that degree of supervision is 1 variable affecting per-
revealed that supervision at 1 year was predicted by education ceived burden of caregivers, either directly or indirectly. For
and scores on the Trail Making Test Part B and digits back- example, Marsh et al studied lifestyle changes that were both
ward. common and distressing to caregivers at 6 months4 and 12
Conclusions: Findings confirm the importance of preinjury months5 after severe TBI. At 6 months, having “less time for
status and measures of working memory and cognitive flexi- myself” was rated as the most common change for caregivers,
bility in predicting functional independence after TBI. The but was not rated as the most distressing. At 12 months, less
SRS appears prone to ceiling effects in persons followed pro- time for oneself was rated both the most common and the most
spectively after moderate to severe TBI. distressing change. This implies that the extra time devoted to
Key Words: Brain injuries; Cognition; Outcomes Research; caring for a family member, or simply being in a constant state
Rehabilitation. of responsibility for someone else, may be more difficult to
cope with as the need becomes chronic. Similarly, Wallace et
al6 found that high proportions of caregivers of persons with
TBI reported having to work less (30%), participating in fewer
leisure pursuits (43%), and having difficulty conducting usual
From Moss Rehabilitation Research Institute (Hart, Fidler-Sheppard) and Depart- activities (67%). Although the lifestyle changes in these studies
ment of Rehabilitation Medicine (Hart), Jefferson Medical College, Thomas Jefferson are not measures of supervision alone, supervision needs may
University, Philadelphia, PA; Kessler Medical Rehabilitation Research and Education
Corp, West Orange, NJ (Millis); Spain Rehabilitation Center, University of Alabama,
comprise a significant portion of the extra time and energy
Birmingham, AL (Novack); Department of Physical Medicine and Rehabilitation, required of caregivers at the expense of other activities. Yet for
Santa Clara Valley Medical Center, San Jose, CA (Englander); and Department of all its potential importance as a clinical construct with impact
Rehabilitation Medicine, University of Washington, Seattle, WA (Bell). on the injured person and the family system, supervision has
Supported by the National Institute on Disability and Rehabilitation Research
(grant nos. H133A70033, H133A980010, H133A980023).
not yet been extensively studied as an outcome of TBI.
No commercial party having a direct financial interest in the results of the research A few descriptive studies have directly measured the amount
supporting this article has or will confer a benefit upon the authors or upon any and nature of supervision required for persons with TBI. For
organization with which the authors are associated. example, Hawkins et al7 performed 3- and 12-month follow-
Reprint requests to Tessa Hart, PhD, Moss Rehabilitation Research Institute, 1200
W Tabor Rd, Philadelphia, PA 19141, e-mail: thart@einstein.edu.
ups on a sample of 55 persons, most with severe TBI. These
0003-9993/03/8402-7442$35.00/0 investigators reported that only one third of their sample was
doi:10.1053/apmr.2003.50023 independent of supervision at 3 months postinjury. By 12

Arch Phys Med Rehabil Vol 84, February 2003

222 NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart

months postinjury, 59% were independent of supervision, but ment of outcome, which was number of falls sustained in the
another 18% needed it full-time or nearly full-time. Granger et hospital setting. Again, measures of executive function ex-
al8 explored aspects of caregiver help and supervision in more plained a significant amount of variance in the real-world
depth by asking 22 community-based persons with TBI and outcome measure.
their caregivers to keep a journal of the amount and type of It stands to reason that both memory and executive function
assistance needed at home. The subjects were fairly evenly would be associated with functional outcomes after TBI. The
divided among 5 supervision levels, ranging from “constant” to ability to learn and retain novel information over time is
“none.” Although the findings of Granger may be difficult to essential to safe, adaptive function in a changing environment.
generalize because of the small sample size, the data suggested Executive function is a catch-all term used to describe a host of
that for those with intense supervision needs, the degree of complex skills related to goal-directed behavior.20 Executive
motor impairment was important for distinguishing levels of skills enable the organism to choose and deploy flexible be-
supervision required. However, for distinguishing among less haviors in response to environmental demands, to regulate
intense levels of supervision, cognitive impairments were more those behaviors via self-monitoring processes, and to sustain
important than physical status. Time postinjury seems to be a plans of action over time. This class of functions is not con-
factor in determining supervision level in longer term outcome sidered to be very well tapped by objective neuropsychologic
studies. For example, Corrigan et al9 followed 95 patients for 5 measures, which are commonly administered under structured
years and reported a decrease in the need for assistance and and standardized conditions requiring little flexibility and de-
supervision from the first year after the injury (60%) to 4 to 5 cision making from the subject. Nonetheless, measures that do
years after the trauma (25%). demand some degree of mental flexibility such as the Wiscon-
The clinical and research literature10 suggests that cognitive sin Card Sorting Test (WCST), the Trail Making Test Part B
and behavioral deficits caused by TBI are more strongly asso- (TMT-B), and measures of fluency or generativity appear fairly
ciated with caregiver burden than are physical impairments. robustly related to activities that demand executive function in
The Wallace6 study reported that of various domains rated by real life.21,22 An excellent example is the demonstration in
the caregiver, only cognition accounted for significant variance multiple studies23-25 of the TMT as a predictor of return to
in caregiver lifestyle change. Similarly, Hawkins et al7 found driving after acquired brain disorder.
that only cognitive function ratings at 3 months postinjury The measurement of supervision level has varied in previous
predicted degree of supervision at 1 year. In a study of persons work on this topic, with most previous studies developing their
with TBI and their families 3 months postinjury, Smith and own system, usually an ordinal scheme for rating the intensity
Schwirian11 found that the combination of impaired cognition of care.7,8 The instrument used in the current investigation, the
and need for supervision was perceived as especially burden- Supervision Rating Scale (SRS), was published by Boake in
some. In a French sample of persons with TBI, Mazaux et al12 1996.26 The SRS is an instrument for rating the degree of
reported that lack of mental flexibility and poor planning (as supervision received on a 13-point ordinal scale from “inde-
rated by an experienced clinician) were associated with long- pendent” to “full-time direct supervision (with patient in phys-
term impairment of “social autonomy” (ie, need for caregiver ical restraints).” In his initial validation study on 114 persons
assistance and supervision). Clinical experience suggests, as with TBI at an average of 4 years postinjury, Boake26 reported
noted by Granger,8 that there is sizeable group of persons with that about 75% of the sample received at least part-time super-
moderate to severe TBI who require supervision for cognitive vision. However, Hall et al27 reported the opposite finding in
or behavioral deficits, but whose physical function is relatively their sample of 48 persons with TBI between 2 and 9 years
intact. In fact, supervising these individuals may be more postinjury: about 71% were at the ceiling, that is, functioning
difficult because they are mobile. Little is known about the without supervision. It is not clear what differences between
specific cognitive deficits that are present in these individuals, these samples accounted for the discrepant findings, and it
and which deficits are most indicative of need for caregiver remains unknown whether similar ceiling effects would be
presence or assistance. found closer to the time of injury (eg, at 1y post-TBI).
In the studies cited earlier, cognitive status was not deter- One aspect of the SRS noted by Boake is that it contains no
mined objectively but was based on caregiver or clinician provision to describe or explain the reasons why the person
ratings (eg, by using the cognitive items on the FIM™ instru- with TBI is, or is not, receiving supervision. Thus, it is of
ment13). However, objective measures of cognitive function interest to examine the correlates of SRS ratings to help elu-
(ie, neuropsychologic test scores) have been shown repeatedly cidate the deficits and impairments that are associated with
to predict real-world functional outcomes. Ratings of func- supervision outcome in this population. For the present study,
tional disability are significantly correlated with scores in a we undertook analyses of SRS ratings performed on a sample
variety of cognitive domains in postacute TBI.14 Neuropsycho- of persons at 1 year after moderate to severe TBI. These
logic testing after TBI provides significant incremental predic- participants, who were enrolled in the Traumatic Brain Injury
tion of vocational status at 1 year postinjury, over and above Model Systems (TBIMS) national database, had also under-
measures of initial injury severity and functional status mea- gone neuropsychologic testing at the same follow-up interval.
sures.15,16 Measures of learning and memory and executive The objectives of the study were 3-fold. First, we wanted
function appear to be overall good predictors of productivity simply to examine the distribution of rated supervision levels,
outcome.17 Outcomes other than productivity and return to both to determine the supervision characteristics of a large,
work have been studied, at varying intervals between testing prospectively followed sample of persons with moderate to
and outcome measurement. For example, Hanks et al18 studied severe TBI and to determine the extent of ceiling effects, if any,
the utility of neuropsychologic testing in inpatient rehabilita- at 1 year postinjury. Second, we wanted to provide clinically
tion for predicting a range of social and functional outcomes at accessible demographic, injury, and neuropsychologic data on
6 months post-TBI. Test scores, particularly in the areas of the characteristics of persons with TBI at different levels of
executive function and memory, predicted outcome over and supervision. To explore characteristics of a clinically signifi-
above the contributions of motor and sensory deficits. Another cant subgroup, we elected to compare subjects at different
study by the same investigators19 used concurrent prediction, levels of supervision in the relative absence of physical dis-
that is, testing conducted during the same time as the measure- ability. Finally, we performed multivariable analyses to esti-


NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart 223

mate the relative contributions of different aspects of neuro- ment in the acute care hospital; the LOC, defined as the interval
psychologic function to variation in supervision level in the in days between the TBI and the date at which the patient
absence of physical care needs, over and above that accounted followed simple commands on 2 consecutive assessments
for by demographic variables and indices of injury severity. within 24 hours; and the duration of posttraumatic amnesia
Based on previous research, we hypothesized that measures of (PTA), defined as the interval in days between the TBI and the
learning, delayed memory, and executive function would pro- first of 2 consecutive (within 72h) scores above 75 on the
vide significant incremental prediction of the need for super- Galveston Orientation and Amnesia Test30 (GOAT). Neuropsy-
vision in persons who did not require supervision for mobility chologic measures were derived from a comprehensive battery
or basic self-care activities. of tests in wide clinical use, which was composed for the
purpose of longitudinal study within the TBIMS project.31 The
METHODS tests in the battery and the scores used in the present study are
in table 1. Outcome measures were also selected from the
Participants comprehensive set of measures administered at 1-year follow-
Participants were selected from persons enrolled in the up. The main outcome variable of interest was the SRS, de-
TBIMS longitudinal database from the 17 TBIMS centers in scribed earlier. Participants’ level of supervision was obtained
the United States. All participants met criteria for inclusion in by interview with the patient and caregiver at follow-up. The
the Model Systems project by having sustained a penetrating or 13 ordinal levels of supervision rated on the original scale are
nonpenetrating TBI as evidenced by loss of consciousness in table 2. A second outcome variable from the national data-
(LOC), focal brain lesion on neuroimaging, or abnormality on base was used to select a subgroup of subjects for further study
neurologic examination consistent with external trauma. All as described later. This was the FIM.13 The FIM is an 18-item
Model Systems enrollees were age 16 or older, received med- rating scale assessing patients’ level of independence in motor,
ical care in a TBIMS-affiliated acute care hospital within 24 self-care, and cognitive items. Each item is rated on a scale of
hours of injury, and were transferred directly from acute care to 1 (total assistance) to 7 (complete independence). Rasch anal-
an affiliated inpatient rehabilitation hospital. All participants ysis has revealed 2 main dimensions underlying FIM scores, a
provided informed consent directly or by legal proxy. physical dimension that includes 13 items rating motor func-
As has been described in detail elsewhere,28 longitudinal tion and self-care abilities, and a cognitive dimension including
data collection for the TBIMS project occurs from acute emer- the 5 cognitive items.32 Neuropsychologic and follow-up data
gency care to long-term follow-up. Initial data collection in- were collected at 12 months post-TBI with a 2-month window
cludes demographic and social information, data on the type in either direction (ie, between 10 and 14mo postinjury).
and severity of the TBI, and other medical data such as com-
plications. Data collected during the rehabilitation stay pertain Data Analysis
primarily to functional status on admission and discharge.
Descriptive statistics were calculated on the whole sample
Follow-up data collection, with which the present investigation
with respect to the 13 SRS levels and the demographic and
is primarily concerned, is done at annual anniversaries of the
injury variables listed previously. The large sample (N 563)
TBI for as long as contact may be maintained. The first-year
was used primarily to characterize the distribution of scores on
follow-up information is collected in a 2- to 3-hour testing and
the SRS. For inferential analyses on the differences related to
interview session with the patient and, if possible, a caregiver
supervision level and the contribution of neuropsychologic
or significant other. This session includes a neuropsychologic
factors, we selected a subset of participants who, at follow-up,
test battery and several outcome measures to assess functional
did not show significant disability with respect to physical or
and social status, including the SRS, which was added to the
self-care function. The purpose of this was to examine the
TBIMS data collection protocol in 1997. Normally, if personal
characteristics of persons receiving supervision in the relative
contact is not possible at follow-up, telephone interviews are
absence of physical assistance. Participants were assumed to be
conducted to obtain a portion of the data set. The current study
physically independent if they received scores of 6 (modified
used only follow-up data collected in person because we were
independence) or 7 (independent) on all 13 motor FIM items:
primarily interested in persons who had undergone neuropsy-
feeding, grooming, bowel and bladder management and toilet-
chologic testing. Thus, in selecting a study sample, we selected
ing, dressing (upper and lower body), transfers (bed, toilet and
from the national database all participants who had received all
tub), bathing, locomotion, and stairs. There were 452 partici-
or any portion of the follow-up neuropsychologic test battery
pants meeting this criterion. This subsample of physically
and had been rated on the SRS. These criteria were met by 563
independent participants was used for all analyses described
participants. A subsample of 452 participants without signifi-
later.
cant physical disability were used for most of the analyses, as
For inferential statistical analyses, the 13 original levels in
described in the Data Analysis section below.
the SRS were collapsed in 2 different ways. For 1 set of
analyses, we used SRS scores to create groups of participants
Measures at 3 clinically meaningful levels of supervision. SRS levels 1
Four types of variables were collected on each participant and 2 were combined into a level considered as “independent.”
from the national database: demographic measures, injury se- Levels 3 through 5 were combined into a level considered
verity variables, neuropsychologic test scores, and outcome “moderate supervision.” The commonality among these 3 lev-
measures. Demographic measures were obtained by chart re- els is that a caregiver may be absent for the time needed to
view and patient/family interview. They included age at injury, work full-time (see table 2). Levels 6 through 13 were com-
gender, race, education, productivity status (eg, employment) bined into a “heavy supervision” level in which a caregiver
at the time of injury, marital status, and primary person with would not be able to work full-time. These 3 levels were used
whom the patient resided at follow-up. Injury variables in- as a grouping variable for chi-square and Kruskal-Wallis tests
cluded the etiology of injury and 3 measures commonly used to to examine differences on selected demographic and injury
estimate the severity of TBI. These were the Glasgow Coma variables and on neuropsychologic test scores. In view of the
Scale29 (GCS) score on admission to the emergency depart- large number of univariate comparisons, Bonferroni correction



Table 1: Neuropsychologic Tests in Follow-Up Battery

Test Description Score Impairment Criterion

GOAT Questions assessing orientation to time, place, and Error points 24
person and recall of recent events
Token Test Measure of auditory comprehension (subject No. correct 37
follows commands using colored tokens)
Logical memory Immediate and 30-min delayed recall of stories No. of story elements 5th percentile for age
immediate/delayed presented auditorially recalled
Digit span, forward and Repetition of digit strings in forward/reverse order; Based on no. of digits 5th percentile for age
backward measure of attention/concentration and repeated
immediate recall
Grooved Pegboard Motor speed, fine coordination; subject places 25 Time (s) 89
pegs in board with dominant hand
Benton Visual Perceptual matching using multiple-choice stimuli No. correct 25
Discrimination Test
Controlled Oral Word Verbal fluency/generativity; subject generates words No. of words (corrected 23
Association Test beginning with specific letters in 1-min trials for age, education)
Rey Auditory Verbal Word list learning: 15 words 5 trials Total no. of words 37
Learning Test recalled
Symbol Digit Visual scanning under timed conditions; subject No. correct responses 36 written, 40 oral
Modalities Test, matches symbols to numbers using written and within time limit
written/oral oral responses, respectively
TMT-A, TMT-B Visuomotor sequencing; subject connects numbers Time (s) 10th percentile for age
in order (Part A), then alternates numbers and
letters, requiring set-shifting (Part B)
Block design Visual construction; subject arranges 3-dimensional No. correct/points for 4
blocks to match designs within time limits speed (corrected for
age)
WCST Reasoning/concept formation, set-shifting; subject No. of perseverative 5th percentile for age,
deduces principles by which to sort cards via responses education level
feedback on performance

was used to set at .003 for the neuropsychologic test score gression model. The dependent variable or outcome variable,
analyses (ie, .05/16 tests .003). supervision level, was dichotomized as either independent
In the next analysis, we examined the relative contribution of (SRS levels 1–2) or supervised (SRS levels 3–13). The demo-
neuropsychologic test performance while controlling for the graphic variables (age, education) were entered first, followed
effects of demographic and injury variables on level of super- by the injury severity variables (length of PTA, LOC). Nine of
vision. For this analysis we used a generalized linear modeling the 16 neuropsychologic test scores were entered last as a
approach in which we initially fitted a sequential logistic re- group. The scores selected were 4 measures of memory (digits

Table 2: Distribution of Ratings on Supervision Rating Scale in Overall Sample (N 563)

SRS Level* n %

1: Lives alone or with nonresponsible others (eg, children) 294 52.2
2: Lives with others who could be responsible, but is unsupervised 93 16.5
3: Supervised overnight, not during day 32 5.7
4: Supervised overnight and part-time during day, may go on independent outings 40 7.1
5: Supervised overnight, part-time during day, unsupervised during full-time work 11 2.0
hours
6: Supervised overnight, part-time during day, caregivers absent 1h at a time, but 35 6.2
less than time needed to work full-time
7: Supervised overnight and during most of day; left alone 1h at a time 18 3.2
8: Full-time indirect supervision; someone always present, checks on patient once 19 3.4
every 30min or less often
9: Same as 8, with overnight safety precautions such as lock on front door 4 0.7
10: Full-time direct supervision; someone always present, checks on patient more than 12 2.1
once per 30min
11: Lives in setting in which exits are physically controlled (eg, locked unit) 5 0.9
12: Same as 11, plus line-of-sight supervision (eg, escape watch) 0 0
13: Patient in physical restraints 0 0

*Defined by Boake.26



forward and backward, Rey Auditory Verbal Learning Test Characteristics of Physically Independent Persons by
[RAVLT] total, logical memory– delayed score), 3 measures of Supervision Level
executive function (TMT-B, Controlled Oral Word Association
Demographic and injury characteristics of the physically
Test [COWAT], WCST perseverative responses), and 2 scores
independent subsample sorted by the 3 supervision groups
expected to vary by overall severity of deficit rather than
(independent, moderate, heavy supervision) are in table 3. The
specific neuropsychologic impairment (TMT-A, Digit Symbol
groups did not differ significantly by age or gender. Three other
Modalities Test–Oral administration).
demographic variables, which are themselves interrelated
We then investigated whether the logit link function used in
(race, education, productivity status prior to injury), showed
logistic regression was appropriate for our data. The logit link
significant overall differences by supervision level. Post hoc
is often compared with the complementary log-log link. The
chi-square tests showed that members of ethnic minorities,
expected value of the response variable is modeled as a linear
persons not productively employed before injury, and persons
combination of the predictor variables by way of a link func-
with less than a high school education were disproportionately
tion. The logit link is (ln[p/(1 p)]), whereas the complemen-
represented in the supervised groups.
tary log-log link function is (ln[ ln(1 )]). The complemen-
With respect to injury characteristics, neither etiology nor
tary log-log function is asymmetrically sigmoidal with the
admission GCS score varied systematically by supervision
upper part of the sigmoid being more elongated in comparison
level. Duration of unconsciousness was significantly shorter for
to the symmetric logit function. We used Stata,a version 7.0,33
the independent group than for each of the 2 supervised groups
to develop our generalized linear models.
(all P .0001, Mann-Whitney tests). Duration of PTA was
RESULTS significantly longer for the moderate group compared with the
independent group (P .001, Mann-Whitney).
Characteristics of the Sample
Descriptive demographic and injury characteristics were cal- Neuropsychologic Characteristics by Supervision Level
culated for the whole sample of 563 participants. The sample The neuropsychologic test scores were analyzed by super-
was predominantly male (72%) with a mean age standard vision level in 2 ways. Scores on each test were compared
deviation (SD) of 36.8 16.0 (range, 16 – 89y). Whites com- across the 3 groups by using Kruskal-Wallis tests. In addition,
prised 66% of the sample and African Americans 24%. A little for each group, the proportion of scores falling into the im-
less than one third (28%) had less than a high school education paired range was calculated and the groups compared by chi-
and another third (31%) had a high school diploma or General square tests. Impaired performance was defined as scores fall-
Educational Development (GED). About half (48%) were sin- ing at or worse than the 5th percentile according to available
gle, and 64% were competitively employed before injury. normative data, or according to other criteria for scores within
These demographic characteristics are typical of samples of the “abnormal range.” These scores were derived from pub-
persons with moderate to severe TBI. In terms of injury char- lished test manuals and, in a few cases, adopted from previous
acteristics, the overall mean GCS score on admission to emer- work performing similar analyses on the same tests.34 For tests
gency care was 9.0 4.3 (range, 3–15), mean LOC was sensitive to age and education, criteria were adjusted by those
8.1 15.9 days (range, 0 –220), and mean length of PTA was factors. The scores used to determine impairment on each test
29.8 25.7 days (range, 0 –234). These values confirm the are in table 1.
predominance of moderate to severe TBI in the sample. The Results of both types of analyses, along with summary
majority of cases were caused by vehicular crashes (68%). statistics for each group, are in table 4. All measures showed an
Falls accounted for an additional 16% and violence-related average pattern of worse performance as intensity of supervi-
injury for 15%. sion increased (ie, worst performance in the heavy supervision
At 1-year follow-up, as is also typical in moderate and group, best performance in the independent group). For all tests
severe TBI, an even smaller proportion of the participants except for the Benton Visual Discrimination Test (BVDT;
reported being competitively employed (29%). The majority performance on which appeared to be near ceiling for all
(83%) were living with relatives or significant others, and 13% groups), overall Kruskal-Wallis test results were significant at
reported living alone. P less than .001. Post hoc tests (Mann-Whitney U) indicated
that all tests showing significant differences discriminated the
Distribution of SRS Scores independent group from 1 or both of the supervision groups.
The distribution of cases in the 13 original SRS levels over Only the COWAT differed significantly between the moderate
the entire sample of 563 participants is in table 2. Slightly over and heavy supervision groups. Perseverative errors on the
half the participants were rated as independent (level 1) at 1 WCST showed a trend toward significance between the 2
year postinjury. Another 16.5% were rated at level 2, which is supervision groups (P .006).
also an independent level because the only difference from Results of the chi-square analyses, comparing the percentage
level 1 is that the patient lives with someone who could be of persons within the impaired range on each test across
responsible if supervision were needed. Thus, about 69% of groups, essentially agreed with the Kruskal-Wallis tests (see
this sample were rated as unsupervised. table 4). Again, results were significant for all tests except the
Of the higher scores indicating that some supervision was BVDT, with the independent group differing from 1 or both
received, several values were infrequently used relative to their supervision groups in all post hoc analyses. However, the
neighboring values (eg, levels 5, 9). No participants in this percentage of impaired in the moderate versus heavy supervi-
sample received either of the 2 highest scores (12, 13). sion groups differed significantly only on the backward digit
As expected, physical and self-care functioning was signif- span measure.
icantly related to level of supervision. SRS score correlated Participants in the 3 groups also differed from each other in
negatively with total motor score on the FIM (Spearman terms of the number of tests on which they scored within the
.45, P .00001). The remainder of the analyses focused impaired range. On average, participants in the independent
on the subsample of 452 participants with no scores on motor group scored in the impaired range on 14% of the tests they
FIM items less than 6. completed (about 2/16 tests, for those completing the entire



Table 3: Demographic and Injury Characteristics of Physically Independent Participants by Supervision Level

Moderate Heavy
Independent Supervision Supervision Overall Group
(n 359) (%) (n 57) (%) (n 36) (%) Comparisons

Age (y)
Mean SD 35.0 14.5 34.7 16.2 36.6 19.7 NS
Range 16–86 16–78 16–89
Gender
Male 259 (80) 39 (12) 25 (8) NS
Female 100 (76) 18 (14) 11 (9)
Race
2
White 262 (84) 31 (10) 20 (6) 11.4, P .005
Ethnic minority 97 (70) 26 (19) 16 (12)
Education
2
High school 82 (69) 21 (18) 15 (13) 13.7, P .005
High school or GED 116 (81) 14 (10) 14 (10)
High school 158 (84) 22 (12) 7 (4)
Productivity status
2
Productive* 296 (82) 40 (11) 26 (7) 6.2, P .05
Nonproductive 63 (70) 17 (19) 10 (11)
Etiology
Vehicular 247 (80) 37 (12) 23 (7) NS
Violence-related 46 (72) 11 (17) 7 (11)
Falls/other 66 (81) 9 (11) 6 (7)
GCS score (emergency admission)
(n 436)
Mean SD 9.3 4.2 8.9 4.4 8.4 4.2 NS
Range 3–15 3–15 3–15
LOC, d (n 542)
Mean SD 4.9 8.8 10.5 11.4 11.7 15.6 KW 28.0, P .00001
Range 0–63 0–38 0–64
Duration of PTA, d (n 416)
Mean SD 24.6 19.3 37.1 25.7 32.7 22.7 KW 13.4, P .001
Range 0–144 5–102 0–94

Abbreviations: NS, not significant; KW, Kruskal-Wallis.
* Includes full-time workers, full-time students, and homemakers.

battery). Those in the moderate supervision group were im- Table 5 presents summary information for the sequential
paired on a mean 27% of completed tests (about 4/16) and cloglog model. A total of 281 subject records contributed to
those in the heavy supervision group were impaired on a mean this analysis by virtue of having complete data sets. Age and
44% (7 tests). These proportions differed between all pairs of education were entered first with education reliably predicting
groups at P less than .01 (Kruskal-Wallis tests). level of supervision. Length of PTA and length of LOC were
entered next, but neither made statistically significant contri-
Sequential Binomial Regression Models butions. The neuropsychologic tests were entered last as a
As noted above, supervision was dichotomized for this anal- group. Only 2 of the 9 tests, digits backward and TMT-B, were
ysis, with participants rated independent (SRS levels 1–2), reliable predictors of supervision level. It was interesting to
coded as 1, and the supervised participants (SRS levels 3–13), note that the sign of the coefficient of digits backward was
coded as 0, in our regression models. Because most participants opposite to what would be predicted on the basis of both
were independent, our dependent variable contained signifi- clinical expectation and its point biserial correlation with the
cantly more 1’s than 0’s. On the basis of this distribution, we ordinal dependent variable, SRS. That is, we would expect that
expected that a complementary log-log model (cloglog) would higher scores on digits backward would be associated with an
fit our data better than a standard logistic regression model. In increased likelihood of independent functioning. Indeed, its
fact, the cloglog had a lower deviance statistic (192.24) than correlation with SRS was rb equal to .15 (P .002). This pattern
the logit link (197.68). Furthermore, the difference between the of findings suggests that digits backward may be a negative or
models’ Bayesian information criterion statistics (5.45) pro- net suppressor variable.35 A suppressor variable enhances the
vided positive evidence for selecting the cloglog model. The importance of other predictor variables by suppressing variance
remaining analyses involved the cloglog model. Substantial that is irrelevant in the prediction of the outcome variable,
multicolinearity among the predictor variables was ruled out by rather than contributing variance in its own right.
calculating the variance inflation factor (VIF) for each; the VIF In terms of evaluating the overall model, receiver operating
provides an index of the strength of the relationship between characteristic (ROC) curve analysis revealed that this model
each predictor variable and all other predictors remaining in the had excellent discrimination (area under the curve .83; fig 1).
equation. The mean VIF for this set of predictors was 1.71, and Overall correct classification was 85%. The prevalence of
the highest VIF for an individual variable was 2.38; all VIFs supervision in this sample of persons with TBI was relatively
were well below 20. low. Deriving models to predict low prevalence events is


Table 4: Neuropsychologic Test Results by Supervision Level

Moderate Heavy Supervision
Independent (Level 1) Supervision (Level 2) (Level 3) Group Differences
Test (n 359) (n 57) (n 36) (at P .003)

GOAT
Median 1.0 5.0 7.0 1 vs 2 1 vs 3
Mean SD 4.5 7.6 10.0 15.3 17.7 21.5
% impaired 1.7 9.1 31.4 1 vs 2 1 vs 3
Token Test
Median 44.0 43.0 40.0
Mean SD 41.9 4.3 40.9 4.4 35.7 10.0 1 vs 3
% impaired 8.1 17.0 42.4 1 vs 3
Logical memory, immediate
Median 22.0 17.5 16.0 1 vs 2 1 vs 3
Mean SD 22.1 8.2 18.6 9.3 15.4 9.4
% impaired 13.5 27.8 48.5 1 vs 3
Logical memory, delayed
Median 18.0 12.5 9.0 1 vs 2 1 vs 3
Mean SD 17.9 8.7 13.6 10.8 10.8 9.0
% impaired 11.6 31.5 40.6 1 vs 2 1 vs 3
Digit span, forward
Median 8.0 7.0 6.0 1 vs 2* 1 vs 3
Mean SD 8.2 2.3 7.3 2.3 6.4 2.4
% impaired 10.9 19.6 31.4 1 vs 3
Digit span, backward
Median 6.0 5.5 4.0 1 vs 3
Mean SD 6.2 2.3 5.8 2.3 4.6 2.4
% impaired 9.1 8.9 34.3 1 vs 3 2 vs 3
Grooved Pegboard
Median 78.0 82.0 100.0 1 vs 3
Mean SD 87.0 34.8 92.7 38.1 117.7 63.7
% impaired 29.1 38.2 64.7 1 vs 3
BVDT
Median 30.0 30.0 28.0 NS
Mean SD 29.3 3.2 29.1 3.7 27.4 3.6
% impaired 12.6 10.9 17.6 NS
COWAT
Median 34.0 27.0 23.5 1 vs 2 1 vs 3 2 vs 3
Mean SD 33.8 10.8 28.9 10.1 22.1 9.0
% impaired 16.2 30.2 50.0 1 vs 3
RAVLT
Median 45.0 38.0 30.5
Mean SD 44.3 11.5 36.8 14.4 30.2 11.6 1 vs 2 1 vs 3
% impaired 29.5 48.1 71.9 1 vs 2* 1 vs 3
SDMT, written
Median 46.0 35.0 29.5
Mean SD 44.5 13.3 35.5 12.1 30.8 12.4 1 vs 2 1 vs 3
% impaired 25.5 52.7 51.9 1 vs 2 1 vs 3
SDMT, oral
Median 50.0 40.0 33.5
Mean SD 51.4 14.8 41.1 15.2 36.3 15.3 1 vs 2 1 vs 3
% impaired 20.1 45.4 62.5 1 vs 2 1 vs 3
TMT-A
Median 29.0 38.0 43.0
Mean SD 34.6 20.4 50.5 35.4 63.0 56.6 1 vs 2 1 vs 3
% impaired 6.3 20.0 28.1 1 vs 2 1 vs 3
TMT-B
Median 69.0 95.5 141.0 1 vs 2 1 vs 3
Mean SD 82.3 48.8 120.7 71.5 159.4 92.0
% impaired 6.5 17.3 37.9 1 vs 3
Block design
Median 10.0 8.0 7.0
Mean SD 10.1 2.9 8.6 3.3 7.4 3.1 1 vs 2 1 vs 3
% impaired 2.0 5.8 14.7 1 vs 3
WCST
Median 10.0 21.0 42.0 1 vs 3 2 vs 3*
Mean SD 19.0 19.6 26.2 23.2 40.9 24.2
% impaired 16.9 24.5 51.9 1 vs 3

Abbreviation: SDMT, Symbol Digit Modalities Test.
* Trend, at P .006


Table 5: Summary of Complementary Log-Log Regression Analysis Predicting Level of Supervision

Predictor Coefficient SE z P z 95% CI

Age .003 .009 0.31 .758 .014 .019
Education .222 .103 2.15 .032 .019 .424
PTA .006 .006 1.06 .289 .017 .005
LOC .001 .012 0.011 .916 .023 .026
Digit span, forward .031 .058 0.53 .596 .083 .145
Digit span, backward .107 .052 2.05 .040 .209 .005
TMT-A .012 .008 1.64 .100 .027 .002
TMT-B .006 .003 2.14 .032 .012 .001
COWAT .015 .011 0.033 .184 .007 .038
RAVLT .010 .011 0.92 .358 .012 .032
SDMT oral .000 .010 0.02 .983 .019 .020
WCST .001 .005 0.27 .789 .012 .009
Logical memory delayed .010 .011 0.90 .370 .012 .033
Constant .505 .890 0.57 .570 1.239 2.249

Abbreviations: SE, standard error; CI, confidence interval.

challenging because one tends to predict more accurately in the found to be at ceiling on the SRS in the study of Hall et al,27
long run by simply using base rates, that is, predicting the most which obtained ratings on 48 subjects between 2 and 9 years
commonly occurring event. Hence, our model had high sensi- after TBI. Although these findings might be interpreted as
tivity (96%) and low specificity (30%) with respect to receipt indicating good outcome for groups of individuals with mod-
of supervision. In other words, in samples such as this in which erate to severe TBI, we must note that, as a measure of
independence is a more common outcome than supervision, community outcome after TBI, the SRS appears to be prone to
statistical models such as the model under study may be most ceiling effects. Furthermore, in the present sample, the ordinal
useful in ruling out patients who will be independent (ie, structure of the original scale was not completely retained. That
specifying who will be supervised) as opposed to ruling in who is, we did not find progressively fewer participants in each
will be independent. defined category of more intensive supervision. Further re-
search may be needed to determine whether the descriptors for
DISCUSSION different levels of this scale represent meaningful increments of
In this sample of persons with moderate and severe TBI who caregiver burden with regard to supervision or whether other
were prospectively followed and who received follow-up neu- aspects of this construct should be emphasized instead.
ropsychologic evaluation within the TBIMS longitudinal The observed relationships between supervision level in
project, we found 69% to be rated as independent of supervi- postacute stages of recovery and demographic factors predating
sion at 1 year postinjury. This value is quite close to the 71% injury (education, race, productivity status) have not been
reported previously, although premorbid factors are increas-
ingly recognized as important in TBI outcome prediction.36,37
In the logistic regression analysis reported here, education was
a stronger predictor than the majority of neuropsychologic
measures. Level of education may be a proxy variable for
general intellectual capacity, which may be called on as a
“reserve” after TBI or other insult to the central nervous
system. It is possible that persons with higher level of educa-
tion have better preinjury executive and organizational abili-
ties, thus a stronger capacity for independent function in com-
munity settings and/or more capacity for developing
compensatory strategies after injury. With respect to the dis-
crepancy between white participants and members of ethnic
minorities, supervision may simply be more available in some
American subcultures that emphasize participation of extended
family members in caring for ill or disabled persons. On the
other hand, members of minority groups have been reported to
experience less favorable outcomes from TBI compared with
whites.38 A higher proportion of persons supervised at 1 year
postinjury might be another reflection of that outcome discrep-
ancy. We also found preinjury productivity status to be related
to postinjury supervision, albeit not as strongly as education or
race. One limitation of the current study is that we did not have
any measure of need for assistance (or supervision) prior to
injury. Thus, it is possible that at least some persons who were
nonproductive at the time of injury were already in need of
assistance from family members. New variables on preinjury
Fig 1. ROC curve showing the model’s discrimination ability. status have been added to the TBIMS data collection protocol



to define better the contribution of premorbid status to outcome do better with supervision, or whether some rated as supervised
assessment in future research on this population. could be seen as overprotected.
With respect to injury severity variables, the stronger rela-
tionship between the durations of the variables reflecting al- CONCLUSION
tered consciousness compared with the initial GCS was not
surprising because the later in the continuum of care a variable Both preinjury characteristics and neuropsychologic vari-
is collected, the more likely it is to be associated with outcome ables are important for understanding supervision received at 1
measures.39 Although unconsciousness and PTA durations did year after TBI. In persons without physical disability, the
not contribute significantly to the regression model, both were assessment of cognitive function, particularly executive func-
significantly different for supervised versus unsupervised per- tion, added to the prediction of supervision level. In the future,
sons in the univariate analysis; independent participants had a further exploration of the scaling characteristics of the SRS
mean coma about half as long as those who received supervi- would help ensure that an accurate representation of supervi-
sion. sion needs is achieved. Further research on the predictors of
Our hypotheses about neuropsychologic predictors of super- long-term supervision requirements from the acute hospital or
vision status were only partially supported. In the univariate rehabilitation phases of recovery would help families and pro-
analyses, nearly all neuropsychologic measures differentiated viders plan and budget for needed resources. Additional re-
supervised from nonsupervised persons; we did not find spec- search is needed to clarify the contribution of cultural, social,
ificity for measures of memory or executive function. How- and financial factors that were not addressed in the present
ever, only a few measures (digit span backward, COWAT, investigation.
WCST) differentiated between persons receiving moderate ver-
sus heavy supervision. These measures have in common that Acknowledgments: We thank members of the TBIMS Neuropsy-
they place demands on mental flexibility and working memory, chology Committee for helpful comments and suggestions during the
important aspects of executive function. In the logistic regres- design of this project.
sion model, which included measures of injury severity and
demographic status and controlled for shared variance among References
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