Neuropsychologic function and level of caregiver supervision

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Neuropsychologic function and level of caregiver supervision

  1. 1. 221The Relationship Between Neuropsychologic Function andLevel of Caregiver Supervision at 1 Year After TraumaticBrain InjuryTessa 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 andneuropsychologic function and level of caregiver supervision at Rehabilitation1 year after traumatic brain injury. Arch Phys Med Rehabil2003;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 80,000supervision 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 strainsurement 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 societalcenters. 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 socialself-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 isindependent of supervision. Participants without significant given to the injured person. Supervision implies the continuousdysfunction on motor FIM were grouped into supervision or intermittent presence of another person to provide physicalgroups differing in intensity of time commitment from care- care, instructions for or set-up of daily living tasks, problemgiver (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 theirables (education, race, productivity prior to injury), duration of TBI, supervision means a major lifestyle change for both thealtered 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. Forand scores on the Trail Making Test Part B and digits back- example, Marsh et al studied lifestyle changes that were bothward. 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 forstatus 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, lessSRS appears prone to ceiling effects in persons followed pro- time for oneself was rated both the most common and the mostspectively 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 stateRehabilitation. 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 studiesment of Rehabilitation Medicine (Hart), Jefferson Medical College, Thomas Jefferson are not measures of supervision alone, supervision needs mayUniversity, Philadelphia, PA; Kessler Medical Rehabilitation Research and EducationCorp, West Orange, NJ (Millis); Spain Rehabilitation Center, University of Alabama, comprise a significant portion of the extra time and energyBirmingham, AL (Novack); Department of Physical Medicine and Rehabilitation, required of caregivers at the expense of other activities. Yet forSanta Clara Valley Medical Center, San Jose, CA (Englander); and Department of all its potential importance as a clinical construct with impactRehabilitation 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 amountsupporting this article has or will confer a benefit upon the authors or upon any and nature of supervision required for persons with TBI. Fororganization 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, 1200W 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
  2. 2. 222 NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hartmonths postinjury, 59% were independent of supervision, but ment of outcome, which was number of falls sustained in theanother 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-worlddepth 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 functionassistance needed at home. The subjects were fairly evenly would be associated with functional outcomes after TBI. Thedivided 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 ofthat for those with intense supervision needs, the degree of complex skills related to goal-directed behavior.20 Executivemotor 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 regulateintense levels of supervision, cognitive impairments were more those behaviors via self-monitoring processes, and to sustainimportant 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 neuropsychologicstudies. For example, Corrigan et al9 followed 95 patients for 5 measures, which are commonly administered under structuredyears 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 doyears 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 Band behavioral deficits caused by TBI are more strongly asso- (TMT-B), and measures of fluency or generativity appear fairlyciated with caregiver burden than are physical impairments. robustly related to activities that demand executive function inThe Wallace6 study reported that of various domains rated by real life.21,22 An excellent example is the demonstration inthe caregiver, only cognition accounted for significant variance multiple studies23-25 of the TMT as a predictor of return toin 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 previouspredicted degree of supervision at 1 year. In a study of persons work on this topic, with most previous studies developing theirwith TBI and their families 3 months postinjury, Smith and own system, usually an ordinal scheme for rating the intensitySchwirian11 found that the combination of impaired cognition of care.7,8 The instrument used in the current investigation, theand need for supervision was perceived as especially burden- Supervision Rating Scale (SRS), was published by Boake insome. In a French sample of persons with TBI, Mazaux et al12 1996.26 The SRS is an instrument for rating the degree ofreported 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 personsassistance and supervision). Clinical experience suggests, as with TBI at an average of 4 years postinjury, Boake26 reportednoted 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 inor behavioral deficits, but whose physical function is relatively their sample of 48 persons with TBI between 2 and 9 yearsintact. In fact, supervising these individuals may be more postinjury: about 71% were at the ceiling, that is, functioningdifficult because they are mobile. Little is known about the without supervision. It is not clear what differences betweenspecific cognitive deficits that are present in these individuals, these samples accounted for the discrepant findings, and itand which deficits are most indicative of need for caregiver remains unknown whether similar ceiling effects would bepresence 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 nomined objectively but was based on caregiver or clinician provision to describe or explain the reasons why the personratings (eg, by using the cognitive items on the FIM™ instru- with TBI is, or is not, receiving supervision. Thus, it is ofment13). 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 withto 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 samplevariety of cognitive domains in postacute TBI.14 Neuropsycho- of persons at 1 year after moderate to severe TBI. Theselogic testing after TBI provides significant incremental predic- participants, who were enrolled in the Traumatic Brain Injurytion 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 wantedfunction 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 toand 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 clinicallytion for predicting a range of social and functional outcomes at accessible demographic, injury, and neuropsychologic data on6 months post-TBI. Test scores, particularly in the areas of the characteristics of persons with TBI at different levels ofexecutive 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 differentstudy 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-Arch Phys Med Rehabil Vol 84, February 2003
  3. 3. NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart 223mate the relative contributions of different aspects of neuro- ment in the acute care hospital; the LOC, defined as the intervalpsychologic function to variation in supervision level in the in days between the TBI and the date at which the patientabsence of physical care needs, over and above that accounted followed simple commands on 2 consecutive assessmentsfor by demographic variables and indices of injury severity. within 24 hours; and the duration of posttraumatic amnesiaBased on previous research, we hypothesized that measures of (PTA), defined as the interval in days between the TBI and thelearning, delayed memory, and executive function would pro- first of 2 consecutive (within 72h) scores above 75 on thevide 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 batteryor 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 theParticipants 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 obtainedthe United States. All participants met criteria for inclusion in by interview with the patient and caregiver at follow-up. Thethe Model Systems project by having sustained a penetrating or 13 ordinal levels of supervision rated on the original scale arenonpenetrating 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 studyneurologic examination consistent with external trauma. All as described later. This was the FIM.13 The FIM is an 18-itemModel 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 ofhours 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, aprovided 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 includingdata collection for the TBIMS project occurs from acute emer- the 5 cognitive items.32 Neuropsychologic and follow-up datagency care to long-term follow-up. Initial data collection in- were collected at 12 months post-TBI with a 2-month windowcludes 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 Analysisprimarily to functional status on admission and discharge. Descriptive statistics were calculated on the whole sampleFollow-up data collection, with which the present investigation with respect to the 13 SRS levels and the demographic andis 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 onfollow-up information is collected in a 2- to 3-hour testing and the SRS. For inferential analyses on the differences related tointerview session with the patient and, if possible, a caregiver supervision level and the contribution of neuropsychologicor 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 orand social status, including the SRS, which was added to the self-care function. The purpose of this was to examine theTBIMS data collection protocol in 1997. Normally, if personal characteristics of persons receiving supervision in the relativecontact is not possible at follow-up, telephone interviews are absence of physical assistance. Participants were assumed to beconducted to obtain a portion of the data set. The current study physically independent if they received scores of 6 (modifiedused 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 andfrom 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 physicallyand had been rated on the SRS. These criteria were met by 563 independent participants was used for all analyses describedparticipants. 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 indescribed 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 participantsMeasures 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 consideredverity 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 toview 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 caregiverat the time of injury, marital status, and primary person with would not be able to work full-time. These 3 levels were usedwhom the patient resided at follow-up. Injury variables in- as a grouping variable for chi-square and Kruskal-Wallis testscluded the etiology of injury and 3 measures commonly used to to examine differences on selected demographic and injuryestimate the severity of TBI. These were the Glasgow Coma variables and on neuropsychologic test scores. In view of theScale29 (GCS) score on admission to the emergency depart- large number of univariate comparisons, Bonferroni correction Arch Phys Med Rehabil Vol 84, February 2003
  4. 4. 224 NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart 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 performancewas 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, followedeffects of demographic and injury variables on level of super- by the injury severity variables (length of PTA, LOC). Nine ofvision. For this analysis we used a generalized linear modeling the 16 neuropsychologic test scores were entered last as aapproach 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.26Arch Phys Med Rehabil Vol 84, February 2003
  5. 5. NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart 225forward and backward, Rey Auditory Verbal Learning Test Characteristics of Physically Independent Persons by[RAVLT] total, logical memory– delayed score), 3 measures of Supervision Levelexecutive function (TMT-B, Controlled Oral Word Association Demographic and injury characteristics of the physicallyTest [COWAT], WCST perseverative responses), and 2 scores independent subsample sorted by the 3 supervision groupsexpected to vary by overall severity of deficit rather than (independent, moderate, heavy supervision) are in table 3. Thespecific neuropsychologic impairment (TMT-A, Digit Symbol groups did not differ significantly by age or gender. Three otherModalities 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), showedlogistic regression was appropriate for our data. The logit link significant overall differences by supervision level. Post hocis 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 personscombination of the predictor variables by way of a link func- with less than a high school education were disproportionatelytion. 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 nortary log-log function is asymmetrically sigmoidal with the admission GCS score varied systematically by supervisionupper part of the sigmoid being more elongated in comparison level. Duration of unconsciousness was significantly shorter forto the symmetric logit function. We used Stata,a version 7.0,33 the independent group than for each of the 2 supervised groupsto 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 Levelculated 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 compareddeviation (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 availablegle, and 64% were competitively employed before injury. normative data, or according to other criteria for scores withinThese 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 previousacteristics, the overall mean GCS score on admission to emer- work performing similar analyses on the same tests.34 For testsgency care was 9.0 4.3 (range, 3–15), mean LOC was sensitive to age and education, criteria were adjusted by those8.1 15.9 days (range, 0 –220), and mean length of PTA was factors. The scores used to determine impairment on each test29.8 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 summarymajority of cases were caused by vehicular crashes (68%). statistics for each group, are in table 4. All measures showed anFalls 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 testssevere 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 atreported living alone. P less than .001. Post hoc tests (Mann-Whitney U) indicated that all tests showing significant differences discriminated theDistribution 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 moderatethe entire sample of 563 participants is in table 2. Slightly over and heavy supervision groups. Perseverative errors on thehalf the participants were rated as independent (level 1) at 1 WCST showed a trend toward significance between the 2year 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 percentagelevel 1 is that the patient lives with someone who could be of persons within the impaired range on each test acrossresponsible if supervision were needed. Thus, about 69% of groups, essentially agreed with the Kruskal-Wallis tests (seethis 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 bothreceived, several values were infrequently used relative to their supervision groups in all post hoc analyses. However, theneighboring 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 innegatively 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 independenton the subsample of 452 participants with no scores on motor group scored in the impaired range on 14% of the tests theyFIM items less than 6. completed (about 2/16 tests, for those completing the entire Arch Phys Med Rehabil Vol 84, February 2003
  6. 6. 226 NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart 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 0–94Abbreviations: 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 sequentialpaired on a mean 27% of completed tests (about 4/16) and cloglog model. A total of 281 subject records contributed tothose in the heavy supervision group were impaired on a mean this analysis by virtue of having complete data sets. Age and44% (7 tests). These proportions differed between all pairs of education were entered first with education reliably predictinggroups 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, wereysis, with participants rated independent (SRS levels 1–2), reliable predictors of supervision level. It was interesting tocoded as 1, and the supervised participants (SRS levels 3–13), note that the sign of the coefficient of digits backward wascoded as 0, in our regression models. Because most participants opposite to what would be predicted on the basis of bothwere independent, our dependent variable contained signifi- clinical expectation and its point biserial correlation with thecantly more 1’s than 0’s. On the basis of this distribution, we ordinal dependent variable, SRS. That is, we would expect thatexpected that a complementary log-log model (cloglog) would higher scores on digits backward would be associated with anfit our data better than a standard logistic regression model. In increased likelihood of independent functioning. Indeed, itsfact, the cloglog had a lower deviance statistic (192.24) than correlation with SRS was rb equal to .15 (P .002). This patternthe logit link (197.68). Furthermore, the difference between the of findings suggests that digits backward may be a negative ormodels’ Bayesian information criterion statistics (5.45) pro- net suppressor variable.35 A suppressor variable enhances thevided positive evidence for selecting the cloglog model. The importance of other predictor variables by suppressing varianceremaining 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 operatingprovides an index of the strength of the relationship between characteristic (ROC) curve analysis revealed that this modeleach 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 ofthe highest VIF for an individual variable was 2.38; all VIFs supervision in this sample of persons with TBI was relativelywere well below 20. low. Deriving models to predict low prevalence events isArch Phys Med Rehabil Vol 84, February 2003
  7. 7. 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 3Abbreviation: SDMT, Symbol Digit Modalities Test.* Trend, at P .006
  8. 8. 228 NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart 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 2.249Abbreviations: 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,27long run by simply using base rates, that is, predicting the most which obtained ratings on 48 subjects between 2 and 9 yearscommonly occurring event. Hence, our model had high sensi- after TBI. Although these findings might be interpreted astivity (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 ofindependence is a more common outcome than supervision, community outcome after TBI, the SRS appears to be prone tostatistical models such as the model under study may be most ceiling effects. Furthermore, in the present sample, the ordinaluseful in ruling out patients who will be independent (ie, structure of the original scale was not completely retained. Thatspecifying who will be supervised) as opposed to ruling in who is, we did not find progressively fewer participants in eachwill 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 otherwere 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 inproject, we found 69% to be rated as independent of supervi- postacute stages of recovery and demographic factors predatingsion 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 protocolArch Phys Med Rehabil Vol 84, February 2003
  9. 9. NEUROPSYCHOLOGIC FUNCTION AND SUPERVISION, Hart 229to define better the contribution of premorbid status to outcome do better with supervision, or whether some rated as supervisedassessment 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- CONCLUSIONtered consciousness compared with the initial GCS was notsurprising 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 1measures.39 Although unconsciousness and PTA durations did year after TBI. In persons without physical disability, thenot 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 SRSmean 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 orvision 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 presentever, 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 theimportant aspects of executive function. In the logistic regres- design of this project.sion model, which included measures of injury severity anddemographic status and controlled for shared variance among Referencespredictor variables, only digit span backward and the TMT-B 1. Thurman D, Alverson C, Dunn K, Guerrero J, Sniezek J. 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