Authors: David Le, MS Shahid Shafi, MD, MPH, FACS Patricia Gwirtz, PhD Monica Bennett, PhD Rustin Reeves, PhD Librada Callender, BA, CCRC Cynthia Dunklin, BS, CCRC Samantha Cleveland, BS
Traumatic Injury
ORIGINAL RESEARCH ARTICLE
Affiliations: From the University of North Texas Health Science Center, Fort Worth (DL, PG, RR); Baylor University Medical Center, Dallas (SS, MB); and Baylor Institution for Rehabilitation, Dallas, Texas (LC, CD, SC).
Effect of Obesity on Motor Functional Outcome of Rehabilitating Traumatic Brain Injury Patients
Correspondence: All correspondence and requests for reprints should be addressed to: Shahid Shafi, MD, MPH, FACS, Center for Clinical Effectiveness, Baylor Scott & White Health, 8080 Central Expressway, Suite 500, Dallas, TX 75206.
Disclosures: Supported by the Department of Education, National Institute on Disability and Rehabilitation Research grant number H133A120098, Traumatic Brain Injury Model Systems. The contents of this report do not necessarily represent the policy of the Department of Education, and endorsement by the federal government should not be assumed. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/15/9408-0627 American Journal of Physical Medicine & Rehabilitation Copyright * 2014 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000222
ABSTRACT Le D, Shafi S, Gwirtz P, Bennett M, Reeves R, Callender L, Dunklin C, Cleveland S: Effect of obesity on motor functional outcome of rehabilitating traumatic brain injury patients. Am J Phys Med Rehabil 2015;94:627Y632.
Objective: The aim of this study was to determine the association between obesity and functional motor outcome of patients undergoing inpatient rehabilitation after traumatic brain injury.
Design: This retrospective study at an urban acute inpatient rehabilitation center screened data from 761 subjects in the Traumatic Brain Injury Model System who were admitted from January 2010 to September 2013. Inclusion criteria consisted of age of 18 years or older and an abnormal Functional Independence Measure motor score. Body mass index was used to determine obesity in the study population. Patients with a body mass index of 30.0 kg/m2 or greater were considered obese.
Results: A total of 372 subjects met the criteria for inclusion in the study. Of these, 54 (13.2%) were obese. Both obese and nonobese patients showed similar improvement in Functional Independence Measure motor score (mean [SD], 30.4 [12.8] for the obese patients, P = 0.115, and 27.3 [13.1] for the nonobese patients). The mean (SD) Functional Independence Measure motor scores at discharge for the obese and nonobese patients were 63.0 (12.6) and 62.3 (10.1) (P = 0.6548), respectively.
Conclusions: Obesity had no adverse impact on motor functional outcomes of the traumatic brain injury patients who underwent inpatient rehabilitation. Therefore, obesity should not be considered an obstacle in inpatient rehabilitation after traumatic brain injury, if patients are able to participate in necessary therapy. Key Words: Body Mass Index, Disability, Functional Independence Measure, Inpatient Rehabilitation
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Obesity in Patients in Traumatic Injury Rehabilitation Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
627
O
besity has reached an epidemic proportion in the United States and has been associated with multiple medical conditions such as high blood pressure, heart disease, osteoarthritis, stroke, disability, and physical discomfort impeding quality-of-life.1 Previous studies have shown that obese patients with traumatic spinal cord injury and orthopedic trauma, as well as those receiving joint replacements, achieve lower functional gains during rehabilitation compared with patients who are not obese.2Y4 However, there has not been much research on the effects of obesity on patients recovering from traumatic brain injury (TBI). Literature regarding obesity and TBI exists within the intensive care unit setting, with findings that include more difficulties for obese patients in the intensive care unit setting compared with nonobese patients. These complications include respiratory failure, deep vein thrombosis, and multisystem organ failure.5 Another study that involves the association between obesity and TBI looks at the association between body mass index (BMI) and TBI after frontal motor vehicle crashes. In the study, it was found that obese passengers who were involved in frontal motor vehicle crashes are more likely to experience a more severe head trauma. In addition, fatal outcomes were found to be more frequent in obese patients.6 Both studies are indicative of obesity and TBI negatively affecting the health of the patient when compared with the nonobese group. However, an investigation on the association between obesity and TBI in the rehabilitation setting would be beneficial in the area of TBI and obesity research. With 1.7 million people sustaining a TBI each year, it is associated with 52,000 deaths and results in 80,000 new patients with permanent disabilities as well as more than $76 billion in direct and indirect costs to society every year.7 In addition to cognitive deficits, patients surviving TBI require a significant amount of rehabilitation to overcome motor deficits associated with TBI, such as loss of coordination, extremity weakness, and balance.8 Obesity can potentially adversely affect recovery from these motor deficits. It is known that carrying excessive body weight may cause biomechanical strain and contributes to joint degeneration.9 Extremity weakness and balance complications from TBI along with biomechanical strain can potentially hinder functional gains. For example, obese patients may find it difficult to undertake rehabilitation because of the amount of strength required to participate in physical therapy and ambulation. They may need specialized equipment and significant assistance with weight bearing. The amount of time spent in therapy may also be limited by the presence
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of concomitant medical conditions, such as diabetes. In previous studies, obese patients in rehabilitation are recorded to have a higher prevalence of diabetes compared with nonobese patients; as a result, therapy may be hindered because of time taken for wound care and blood glucose.9 The purpose of this study was to determine the association between obesity and recovery of motor functions after TBI in acute inpatient rehabilitation.
METHODS This retrospective study was undertaken at an urban acute inpatient rehabilitation center after approval from the local institutional review board. Subjects were a part of the Traumatic Brain Injury Model Systems and were admitted between January 2010 and September 2013. The Traumatic Brain Injury Model Systems is a project funded by the United States Department of Education National Institute on Disability and Rehabilitation Research.10 It is a longitudinal multicenter study that examines the outcomes and the course of recovery of patients discharged from inpatient rehabilitation.
Patient Selection The medical records of 761 subjects enrolled in the Traumatic Brain Injury Model Systems at a single rehabilitation institute were screened for inclusion in the study. Inclusion criteria consisted of age of 18 years or older and an abnormal admission Functional Independence Measure (FIM) motor score. An abnormal FIM motor score comprises any score other than a perfect score of 7 of each component assessed. Exclusion criteria consisted of the following: 1. Deaths during inpatient rehabilitation 2. Concomitant nontraumatic neurologic deficits 3. Incomplete information on FIM motor score, height, or weight 4. Underweight patients with BMI of less than 18.5 kg/m2 Underweight patients were excluded from the analysis because of possible confounding effects on functional outcome. Patients with missing information on height and weight (330 subjects) or FIM motor scores at admission or discharge (7 subjects) were excluded. Patients younger than 18 years were excluded from the study (15 subjects). Pediatric BMI is calculated differently than adult BMI, in which age and sex are taken into account. To determine whether the pediatric subject is truly obese, further evaluation of skinfold thickness and assessments of diet would be needed.11 No subjects were excluded because of concomitant nontraumatic
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 8, August 2015 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
FIGURE 1 Patient selection.
neurologic deficits and/or deaths during rehabilitation. These criteria identified 372 subjects who constituted the study population.
locomotion, with the highest possible score of 91 and the lowest possible score of 13.8
Measurement of Obesity Data Collection Data on demographics, severity of TBI, as well as functional status at admission and discharge were extracted from the Traumatic Brain Injury Model Systems database. These data were previously collected by trained personnel using a standardized methodology, using a combination of chart review and patient interviews. Additional data on height and weight at admission to inpatient rehabilitation were extracted manually from the patients’ electronic health records.
Measurement of Motor Functions The FIM instrument is the most commonly used functional assessment tool to measure disability.12 The FIM instrument measures the Btype and amount of assistance required for a person with a disability to perform basic life activities.[13 The FIM instrument is scored on a 7-point scale. The minimum score of 1 in a category indicates Bcomplete dependence,[ and a maximum score of 7 in a category indicates Bcomplete independence.[ The FIM instrument examines two different domains: cognitive and motor, with each domain containing multiple areas. The FIM motor domain includes physical functions such as grooming, eating, toileting, and www.ajpmr.com
BMI was used to determine obesity in the study population. Height (meters) and weight (kilograms) were extracted and used to calculate BMI (weight in kilograms divided by the square of height in meters). The Centers for Disease Control and Prevention guidelines define obesity as a BMI of 30.0 kg/m2 or greater.14 The subjects were categorized as nonobese if their BMI was between 18.5 and 29.9 kg/m2 and obese if their BMI was 30.0 kg/m2 or greater.
Data Analysis The primary outcome of interest was change in FIM motor at discharge for the obese vs. nonobese patients. FIM efficiency was also calculated as change in FIM motor score from admission to discharge per day of inpatient rehabilitation. Data were summarized using mean and standard deviation or counts and percentages, as appropriate. Differences between groups were evaluated using Student’s t tests for continuous data and W2 tests for categorical data. If appropriate assumptions were not met, Wilcoxon tests or Fisher’s exact tests were used instead. Linear regression was used to measure the relationship between obesity and FIM motor at discharge while controlling for age, sex, race, marital status, education status, insurance status, socioeconomic status Obesity in Patients in Traumatic Injury Rehabilitation
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
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TABLE 1 Demographic data Variable
Nonobese (n = 318)
Obese (n = 54)
P
47.1 (21.0) 115 (36) 243 (76) 116 (36) 238 (75) 224 (70) 23.9 (3.0) 35.7 (14.7) 13.2 (6.8) 11.6 (4.0) 18 (11Y25) 313 (98)
51.6 (17.5) 16 (30) 37 (69) 29 (53) 45 (83) 44 (81) 33.7 (3.1) 31.9 (13.9) 14.9 (6.6) 11.7 (4.1) 21 (10Y30) 54 (100)
0.1326 0.3527 0.2137 0.0164 0.1763 0.0946 G0.0001 0.0831 0.0915 0.8725 0.2295b 0.3536
Age, mean (SD), yrs Minority race, n (%) Male sex, n (%) Married, n (%) Educational status: high school diploma, n (%) Insurance, n (%) BMI, mean (SD), kg/m2 FIM motor at admission, mean (SD) FIM cognition at admission, mean (SD) GCS at trauma admission,a mean (SD) Days from injury to rehabilitation, n (IQR) Mechanism of injury: nonpenetrating, n (%)
a For nonobese, n = 231; for obese, n = 42. Missing values are a result of patients being intubated, chemically paralyzed, or sedated. b The nonparametric Wilcoxon test was used for analysis of this value. GCS, Glasgow Coma Scale; IQR, interquartile range.
(using geocoding of residence), mechanism of TBI, as well as FIM motor and cognition scores at admission. Analysis was performed with SAS 9.3 using a P G 0.05 significance level.
with FIM motor at discharge (Table 3). Higher FIM motor scores at admission, education level of high school diploma or higher, younger age, and shorter length of stay were associated with higher FIM motor scores at discharge.
RESULTS In the study population, there were 54 obese patients (13.2%; Fig. 1). The obese patients were significantly more likely to be older and married (Table 1). There were no other significant differences between the two patient groups. The mean (SD) FIM motor scores at admission for the obese and nonobese patients were 31.9 (13.9) and 35.7 (14.7), respectively, but the difference was not statistically significant (Table 1). Both groups showed similar improvement in FIM motor scores during inpatient rehabilitation (Table 2, Fig. 2). FIM motor at discharge and FIM efficiency were also similar between the two groups (Table 2). Length of stay was somewhat higher for the obese group, but the difference did not reach statistical significance. Multivariate regression analysis revealed that obesity was not associated
DISCUSSION Currently, there are no comparable data on how BMI influences the rehabilitation of people with TBI. The main finding of the study is that obesity is not adversely associated with recovery of motor functions after TBI among patients who undergo inpatient rehabilitation. This is contrary to previous studies in non-TBI patients that suggested that obesity hampered recovery of motor functions during rehabilitation.2Y4 The mean (SD) FIM motor scores at admission for the obese and nonobese patients were 31.9 (13.9) and 35.7 (14.7), respectively. This was found to be consistent with other studies involving obese patients in rehabilitative settings such as total hip arthroplasty and orthopedic trauma because it was found that FIM motor score at admission tended to be lower in the obese group
TABLE 2 Patient outcomes Variable
Nonobese (n = 318)
FIM motor at discharge, mean (SD) FIM motor change Mean (SD) Median (IQR) LOS in rehabilitation, median (IQR), days FIM motor efficiency, mean (SD)
Obese (n = 54)
P
63.0 (12.6)
62.3 (10.1)
0.6548
27.3 (13.1) 26.0 (18.0Y37.0) 17 (13Y27) 1.5 (0.8)
30.4 (12.8) 27.0 (21.0Y40.0) 21 (14Y30) 1.5 (0.7)
0.1150 0.1412a 0.2015a 0.8985
a
The nonparametric Wilcoxon test was used for analysis of these values. IQR, interquartile range; LOS, length of stay.
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Am. J. Phys. Med. Rehabil. & Vol. 94, No. 8, August 2015 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
FIGURE 2 Box plots of change in FIM motor score from admission to discharge. as opposed to the nonobese group.3,9 The median length of stay for the obese patients was 4 days longer than that for the nonobese patients. Although this difference was not statistically significant, it may be clinically and financially relevant. It suggests that obese patients need longer to achieve their rehabilitation goals because of the fact that admission FIM scores tend to be lower in the obese group. The findings of this study in contrast to other studies bring forth a number of implications. The first is that motor deficits in patients with TBI are anatomically and physiologically different from those as a result of orthopedic injuries. In the latter group of patients, trauma is directly affecting the motor functioning parts (knee and hip). As stated before, it is known that carrying excessive body weight may cause biomechanical strain and contributes to joint degeneration, and these parts are also weight bearing and are weakened by the presence
of obesity.9 Age was the difference between this study and the studies involving arthroplasty. The population that underwent arthroplastic surgeries was significantly older as opposed to the population of this study, making it a possible contributable factor for the lack of difference in the obese and nonobese groups. Another possible explanation is that the most important determinant of motor function in patients with TBI is the severity of damage caused by TBI. In fact, the regression analysis suggests that functional status at admission to inpatient rehabilitation was one of the strongest predictors of functional status at discharge. This effect may overshadow any adverse impact of obesity on motor functions. Another explanation may be that healthcare facilities, such as the one in this study, have started to recognize the needs of their obese patients by acquiring special equipment, such as bariatric beds and special sling lifts. Clinical providers are also trained to treat obese
TABLE 3 Predictors of FIM motor at discharge Variable Obese Admission FIM motor Age Male sex Minority race/ethnicity Married HS diploma Insurance Blunt injury Rehabilitation LOS Geo unit quality score Admission FIM cognition
Estimate
SE
P
1.99 0.41 j0.18 1.80 j2.40 2.37 5.20 j2.17 j6.01 j0.18 j0.02 j0.21
1.94 0.07 0.04 1.70 1.59 1.50 1.75 1.84 5.75 0.08 0.04 0.16
0.3066 G0.00001 G0.0001 0.2888 0.1304 0.116 0.0032 0.2387 0.2972 0.0190 0.48385676 0.1985
R2 = 0.373. HS, high school; LOS, length of stay; R2, coefficient of determination.
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Obesity in Patients in Traumatic Injury Rehabilitation Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
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patients. With these accommodations, it is possible that obesity no longer interferes with patients’ rehabilitation.The rehabilitation center in which data were collected had the equipment and the trained personnel to provide such aid that could be contributable to the lack of significant difference in outcome between the obese and nonobese patients. Another likely explanation of this study’s findings is that patients are admitted to inpatient rehabilitation only if they are able to participate in several hours of therapy daily. Obesity may not play a role in this patient population. In other words, obese patients who are well enough to be admitted to inpatient rehabilitation are likely not hampered by their obesity. This study has a few limitations that should be acknowledged. It is a retrospective analysis with all its inherent limitations. It is a study with negative findings with a risk for type II error, that is, inability to find a difference when one exists. This may be a result of a small sample of obese patients in this population. A single-center experience may not be generalizable to patients treated at other centers, especially if centers have not similarly adopted special equipment to accommodate obese patients. A multicentered study looking at this subject would provide a larger sample and a more accurate depiction; however, because of resource and time restraints, this study could not provide the collaboration of a multicentered study. There is also a possibility of a selection bias because only patients who are able to participate in rehabilitation are admitted to inpatient rehabilitation facilities. Obese TBI patients have more complications during acute care hospitalization compared with nonobese patients and, as a result, may not be able to participate in rehabilitation.4 It is not known whether obese TBI patients were as likely as nonobese patients to be sent to rehabilitation from trauma centers. The effect of comorbidities was not investigated in this study because of lack of data for the vast majority of subjects. Analysis of comorbidities in both groups would examine levels of health among the sample group and determine whether the comorbidities have an effect on functional outcome. Lastly, a large number of patients were excluded because of lack of data on height and weight, which may bias the results.
CONCLUSIONS The findings of this study suggest that obesity had no adverse impact on motor functional outcomes of TBI patients who underwent inpatient rehabilitation. Hence, obesity should not be considered a hindrance in inpatient rehabilitation after TBI.
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ACKNOWLEDGMENTS
The authors thank Angela Welch, clinical system analyst of the Baylor Institute for Rehabilitation, for assistance in obtaining the necessary electronic records and Kelli R. Trungale, MLS, ELS, Baylor Scott & White Health, for editorial assistance. REFERENCES 1. Centers for Disease Control and Prevention: Adult obesity facts. Available at: http://www.cdc.gov/obesity/ data/adult.html. Accessed April 15, 2014 2. Stenson KW, Deutsch A, Heinemann AW, et al: Obesity and inpatient rehabilitation outcomes for patients with a traumatic spinal cord injury. Arch Phys Med Rehabil 2011;92:384Y90 3. Vincent HK, Seay AN, Vincent KR, et al: Effects of obesity on rehabilitation outcomes after orthopedic trauma. Am J Phys Med Rehabil 2012;91:1051Y9 4. Vincent HK, Vincent KR: Obesity and inpatient rehabilitation outcomes following knee arthroplasty: A multicenter study. Obesity 2008;16:130Y6 5. Brown CV, Rhee P, Neville AL, et al: Obesity and traumatic brain injury. J Trauma 2006;61:572Y6 6. Tagliaferri F, Compagnone C, Yoganandan N, et al: Traumatic brain injury after frontal crashes: Relationship with body mass index. J Trauma 2009; 66:727Y9 7. Centers for Disease Control and Prevention: Injury prevention & control: Traumatic brain injury. Available at: http://www.cdc.gov/TraumaticBrainInjury/data/ index.html. Accessed April 8, 2014 8. Mayo Clinic Staff: Traumatic brain injury. Available at: http://www.mayoclinic.com/health/traumatic-braininjury/DS00552/DSECTION=symptoms. Accessed April 8, 2014 9. Vincent HK, Weng JP, Vincent KR: Effect of obesity on inpatient rehabilitation outcomes after total hip arthroplasty. Obesity 2007;15:522Y30 10. National Institute on Disability and Rehabilitation Research: The Traumatic Brain Injury Model Systems. Available at: https://www.tbindsc.org/StaticFiles/ Documents/TBIModel%20SystemsBrochure2010.pdf. Accessed April 9, 2014 11. Centers for Disease Control and Prevention: About BMI for children and teens. Available at: http://www. cdc.gov/healthyweight/assessing/bmi/childrens_bmi/ about_childrens_bmi.html. Accessed June 7, 2014 12. DeCuypere M, Klimo P Jr: Spectrum of traumatic brain injury from mild to severe. Surg Clin North Am 2012;92:939Y57 13. Cournan M: Use of the Functional Independence Measure for outcomes measurement in acute inpatient rehabilitation. Rehabil Nurs 2011;36:111Y7 14. Centers for Disease Control and Prevention: About BMI for adults. Available at: http://www.cdc.gov/ healthyweight/assessing/bmi/adult_bmi/index.html. Accessed April 8, 2014
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 8, August 2015 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Traumatic Injury
ORIGINAL RESEARCH ARTICLE
Affiliations: From the University of North Texas Health Science Center, Fort Worth (DL, PG, RR); Baylor University Medical Center, Dallas (SS, MB); and Baylor Institution for Rehabilitation, Dallas, Texas (LC, CD, SC).
Effect of Obesity on Motor Functional Outcome of Rehabilitating Traumatic Brain Injury Patients
Correspondence: All correspondence and requests for reprints should be addressed to: Shahid Shafi, MD, MPH, FACS, Center for Clinical Effectiveness, Baylor Scott & White Health, 8080 Central Expressway, Suite 500, Dallas, TX 75206.
Disclosures: Supported by the Department of Education, National Institute on Disability and Rehabilitation Research grant number H133A120098, Traumatic Brain Injury Model Systems. The contents of this report do not necessarily represent the policy of the Department of Education, and endorsement by the federal government should not be assumed. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/15/9408-0627 American Journal of Physical Medicine & Rehabilitation Copyright * 2014 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000222
ABSTRACT Le D, Shafi S, Gwirtz P, Bennett M, Reeves R, Callender L, Dunklin C, Cleveland S: Effect of obesity on motor functional outcome of rehabilitating traumatic brain injury patients. Am J Phys Med Rehabil 2015;94:627Y632.
Objective: The aim of this study was to determine the association between obesity and functional motor outcome of patients undergoing inpatient rehabilitation after traumatic brain injury.
Design: This retrospective study at an urban acute inpatient rehabilitation center screened data from 761 subjects in the Traumatic Brain Injury Model System who were admitted from January 2010 to September 2013. Inclusion criteria consisted of age of 18 years or older and an abnormal Functional Independence Measure motor score. Body mass index was used to determine obesity in the study population. Patients with a body mass index of 30.0 kg/m2 or greater were considered obese.
Results: A total of 372 subjects met the criteria for inclusion in the study. Of these, 54 (13.2%) were obese. Both obese and nonobese patients showed similar improvement in Functional Independence Measure motor score (mean [SD], 30.4 [12.8] for the obese patients, P = 0.115, and 27.3 [13.1] for the nonobese patients). The mean (SD) Functional Independence Measure motor scores at discharge for the obese and nonobese patients were 63.0 (12.6) and 62.3 (10.1) (P = 0.6548), respectively.
Conclusions: Obesity had no adverse impact on motor functional outcomes of the traumatic brain injury patients who underwent inpatient rehabilitation. Therefore, obesity should not be considered an obstacle in inpatient rehabilitation after traumatic brain injury, if patients are able to participate in necessary therapy. Key Words: Body Mass Index, Disability, Functional Independence Measure, Inpatient Rehabilitation
www.ajpmr.com
Obesity in Patients in Traumatic Injury Rehabilitation Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
627
O
besity has reached an epidemic proportion in the United States and has been associated with multiple medical conditions such as high blood pressure, heart disease, osteoarthritis, stroke, disability, and physical discomfort impeding quality-of-life.1 Previous studies have shown that obese patients with traumatic spinal cord injury and orthopedic trauma, as well as those receiving joint replacements, achieve lower functional gains during rehabilitation compared with patients who are not obese.2Y4 However, there has not been much research on the effects of obesity on patients recovering from traumatic brain injury (TBI). Literature regarding obesity and TBI exists within the intensive care unit setting, with findings that include more difficulties for obese patients in the intensive care unit setting compared with nonobese patients. These complications include respiratory failure, deep vein thrombosis, and multisystem organ failure.5 Another study that involves the association between obesity and TBI looks at the association between body mass index (BMI) and TBI after frontal motor vehicle crashes. In the study, it was found that obese passengers who were involved in frontal motor vehicle crashes are more likely to experience a more severe head trauma. In addition, fatal outcomes were found to be more frequent in obese patients.6 Both studies are indicative of obesity and TBI negatively affecting the health of the patient when compared with the nonobese group. However, an investigation on the association between obesity and TBI in the rehabilitation setting would be beneficial in the area of TBI and obesity research. With 1.7 million people sustaining a TBI each year, it is associated with 52,000 deaths and results in 80,000 new patients with permanent disabilities as well as more than $76 billion in direct and indirect costs to society every year.7 In addition to cognitive deficits, patients surviving TBI require a significant amount of rehabilitation to overcome motor deficits associated with TBI, such as loss of coordination, extremity weakness, and balance.8 Obesity can potentially adversely affect recovery from these motor deficits. It is known that carrying excessive body weight may cause biomechanical strain and contributes to joint degeneration.9 Extremity weakness and balance complications from TBI along with biomechanical strain can potentially hinder functional gains. For example, obese patients may find it difficult to undertake rehabilitation because of the amount of strength required to participate in physical therapy and ambulation. They may need specialized equipment and significant assistance with weight bearing. The amount of time spent in therapy may also be limited by the presence
628
Le et al.
of concomitant medical conditions, such as diabetes. In previous studies, obese patients in rehabilitation are recorded to have a higher prevalence of diabetes compared with nonobese patients; as a result, therapy may be hindered because of time taken for wound care and blood glucose.9 The purpose of this study was to determine the association between obesity and recovery of motor functions after TBI in acute inpatient rehabilitation.
METHODS This retrospective study was undertaken at an urban acute inpatient rehabilitation center after approval from the local institutional review board. Subjects were a part of the Traumatic Brain Injury Model Systems and were admitted between January 2010 and September 2013. The Traumatic Brain Injury Model Systems is a project funded by the United States Department of Education National Institute on Disability and Rehabilitation Research.10 It is a longitudinal multicenter study that examines the outcomes and the course of recovery of patients discharged from inpatient rehabilitation.
Patient Selection The medical records of 761 subjects enrolled in the Traumatic Brain Injury Model Systems at a single rehabilitation institute were screened for inclusion in the study. Inclusion criteria consisted of age of 18 years or older and an abnormal admission Functional Independence Measure (FIM) motor score. An abnormal FIM motor score comprises any score other than a perfect score of 7 of each component assessed. Exclusion criteria consisted of the following: 1. Deaths during inpatient rehabilitation 2. Concomitant nontraumatic neurologic deficits 3. Incomplete information on FIM motor score, height, or weight 4. Underweight patients with BMI of less than 18.5 kg/m2 Underweight patients were excluded from the analysis because of possible confounding effects on functional outcome. Patients with missing information on height and weight (330 subjects) or FIM motor scores at admission or discharge (7 subjects) were excluded. Patients younger than 18 years were excluded from the study (15 subjects). Pediatric BMI is calculated differently than adult BMI, in which age and sex are taken into account. To determine whether the pediatric subject is truly obese, further evaluation of skinfold thickness and assessments of diet would be needed.11 No subjects were excluded because of concomitant nontraumatic
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 8, August 2015 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
FIGURE 1 Patient selection.
neurologic deficits and/or deaths during rehabilitation. These criteria identified 372 subjects who constituted the study population.
locomotion, with the highest possible score of 91 and the lowest possible score of 13.8
Measurement of Obesity Data Collection Data on demographics, severity of TBI, as well as functional status at admission and discharge were extracted from the Traumatic Brain Injury Model Systems database. These data were previously collected by trained personnel using a standardized methodology, using a combination of chart review and patient interviews. Additional data on height and weight at admission to inpatient rehabilitation were extracted manually from the patients’ electronic health records.
Measurement of Motor Functions The FIM instrument is the most commonly used functional assessment tool to measure disability.12 The FIM instrument measures the Btype and amount of assistance required for a person with a disability to perform basic life activities.[13 The FIM instrument is scored on a 7-point scale. The minimum score of 1 in a category indicates Bcomplete dependence,[ and a maximum score of 7 in a category indicates Bcomplete independence.[ The FIM instrument examines two different domains: cognitive and motor, with each domain containing multiple areas. The FIM motor domain includes physical functions such as grooming, eating, toileting, and www.ajpmr.com
BMI was used to determine obesity in the study population. Height (meters) and weight (kilograms) were extracted and used to calculate BMI (weight in kilograms divided by the square of height in meters). The Centers for Disease Control and Prevention guidelines define obesity as a BMI of 30.0 kg/m2 or greater.14 The subjects were categorized as nonobese if their BMI was between 18.5 and 29.9 kg/m2 and obese if their BMI was 30.0 kg/m2 or greater.
Data Analysis The primary outcome of interest was change in FIM motor at discharge for the obese vs. nonobese patients. FIM efficiency was also calculated as change in FIM motor score from admission to discharge per day of inpatient rehabilitation. Data were summarized using mean and standard deviation or counts and percentages, as appropriate. Differences between groups were evaluated using Student’s t tests for continuous data and W2 tests for categorical data. If appropriate assumptions were not met, Wilcoxon tests or Fisher’s exact tests were used instead. Linear regression was used to measure the relationship between obesity and FIM motor at discharge while controlling for age, sex, race, marital status, education status, insurance status, socioeconomic status Obesity in Patients in Traumatic Injury Rehabilitation
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
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TABLE 1 Demographic data Variable
Nonobese (n = 318)
Obese (n = 54)
P
47.1 (21.0) 115 (36) 243 (76) 116 (36) 238 (75) 224 (70) 23.9 (3.0) 35.7 (14.7) 13.2 (6.8) 11.6 (4.0) 18 (11Y25) 313 (98)
51.6 (17.5) 16 (30) 37 (69) 29 (53) 45 (83) 44 (81) 33.7 (3.1) 31.9 (13.9) 14.9 (6.6) 11.7 (4.1) 21 (10Y30) 54 (100)
0.1326 0.3527 0.2137 0.0164 0.1763 0.0946 G0.0001 0.0831 0.0915 0.8725 0.2295b 0.3536
Age, mean (SD), yrs Minority race, n (%) Male sex, n (%) Married, n (%) Educational status: high school diploma, n (%) Insurance, n (%) BMI, mean (SD), kg/m2 FIM motor at admission, mean (SD) FIM cognition at admission, mean (SD) GCS at trauma admission,a mean (SD) Days from injury to rehabilitation, n (IQR) Mechanism of injury: nonpenetrating, n (%)
a For nonobese, n = 231; for obese, n = 42. Missing values are a result of patients being intubated, chemically paralyzed, or sedated. b The nonparametric Wilcoxon test was used for analysis of this value. GCS, Glasgow Coma Scale; IQR, interquartile range.
(using geocoding of residence), mechanism of TBI, as well as FIM motor and cognition scores at admission. Analysis was performed with SAS 9.3 using a P G 0.05 significance level.
with FIM motor at discharge (Table 3). Higher FIM motor scores at admission, education level of high school diploma or higher, younger age, and shorter length of stay were associated with higher FIM motor scores at discharge.
RESULTS In the study population, there were 54 obese patients (13.2%; Fig. 1). The obese patients were significantly more likely to be older and married (Table 1). There were no other significant differences between the two patient groups. The mean (SD) FIM motor scores at admission for the obese and nonobese patients were 31.9 (13.9) and 35.7 (14.7), respectively, but the difference was not statistically significant (Table 1). Both groups showed similar improvement in FIM motor scores during inpatient rehabilitation (Table 2, Fig. 2). FIM motor at discharge and FIM efficiency were also similar between the two groups (Table 2). Length of stay was somewhat higher for the obese group, but the difference did not reach statistical significance. Multivariate regression analysis revealed that obesity was not associated
DISCUSSION Currently, there are no comparable data on how BMI influences the rehabilitation of people with TBI. The main finding of the study is that obesity is not adversely associated with recovery of motor functions after TBI among patients who undergo inpatient rehabilitation. This is contrary to previous studies in non-TBI patients that suggested that obesity hampered recovery of motor functions during rehabilitation.2Y4 The mean (SD) FIM motor scores at admission for the obese and nonobese patients were 31.9 (13.9) and 35.7 (14.7), respectively. This was found to be consistent with other studies involving obese patients in rehabilitative settings such as total hip arthroplasty and orthopedic trauma because it was found that FIM motor score at admission tended to be lower in the obese group
TABLE 2 Patient outcomes Variable
Nonobese (n = 318)
FIM motor at discharge, mean (SD) FIM motor change Mean (SD) Median (IQR) LOS in rehabilitation, median (IQR), days FIM motor efficiency, mean (SD)
Obese (n = 54)
P
63.0 (12.6)
62.3 (10.1)
0.6548
27.3 (13.1) 26.0 (18.0Y37.0) 17 (13Y27) 1.5 (0.8)
30.4 (12.8) 27.0 (21.0Y40.0) 21 (14Y30) 1.5 (0.7)
0.1150 0.1412a 0.2015a 0.8985
a
The nonparametric Wilcoxon test was used for analysis of these values. IQR, interquartile range; LOS, length of stay.
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FIGURE 2 Box plots of change in FIM motor score from admission to discharge. as opposed to the nonobese group.3,9 The median length of stay for the obese patients was 4 days longer than that for the nonobese patients. Although this difference was not statistically significant, it may be clinically and financially relevant. It suggests that obese patients need longer to achieve their rehabilitation goals because of the fact that admission FIM scores tend to be lower in the obese group. The findings of this study in contrast to other studies bring forth a number of implications. The first is that motor deficits in patients with TBI are anatomically and physiologically different from those as a result of orthopedic injuries. In the latter group of patients, trauma is directly affecting the motor functioning parts (knee and hip). As stated before, it is known that carrying excessive body weight may cause biomechanical strain and contributes to joint degeneration, and these parts are also weight bearing and are weakened by the presence
of obesity.9 Age was the difference between this study and the studies involving arthroplasty. The population that underwent arthroplastic surgeries was significantly older as opposed to the population of this study, making it a possible contributable factor for the lack of difference in the obese and nonobese groups. Another possible explanation is that the most important determinant of motor function in patients with TBI is the severity of damage caused by TBI. In fact, the regression analysis suggests that functional status at admission to inpatient rehabilitation was one of the strongest predictors of functional status at discharge. This effect may overshadow any adverse impact of obesity on motor functions. Another explanation may be that healthcare facilities, such as the one in this study, have started to recognize the needs of their obese patients by acquiring special equipment, such as bariatric beds and special sling lifts. Clinical providers are also trained to treat obese
TABLE 3 Predictors of FIM motor at discharge Variable Obese Admission FIM motor Age Male sex Minority race/ethnicity Married HS diploma Insurance Blunt injury Rehabilitation LOS Geo unit quality score Admission FIM cognition
Estimate
SE
P
1.99 0.41 j0.18 1.80 j2.40 2.37 5.20 j2.17 j6.01 j0.18 j0.02 j0.21
1.94 0.07 0.04 1.70 1.59 1.50 1.75 1.84 5.75 0.08 0.04 0.16
0.3066 G0.00001 G0.0001 0.2888 0.1304 0.116 0.0032 0.2387 0.2972 0.0190 0.48385676 0.1985
R2 = 0.373. HS, high school; LOS, length of stay; R2, coefficient of determination.
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patients. With these accommodations, it is possible that obesity no longer interferes with patients’ rehabilitation.The rehabilitation center in which data were collected had the equipment and the trained personnel to provide such aid that could be contributable to the lack of significant difference in outcome between the obese and nonobese patients. Another likely explanation of this study’s findings is that patients are admitted to inpatient rehabilitation only if they are able to participate in several hours of therapy daily. Obesity may not play a role in this patient population. In other words, obese patients who are well enough to be admitted to inpatient rehabilitation are likely not hampered by their obesity. This study has a few limitations that should be acknowledged. It is a retrospective analysis with all its inherent limitations. It is a study with negative findings with a risk for type II error, that is, inability to find a difference when one exists. This may be a result of a small sample of obese patients in this population. A single-center experience may not be generalizable to patients treated at other centers, especially if centers have not similarly adopted special equipment to accommodate obese patients. A multicentered study looking at this subject would provide a larger sample and a more accurate depiction; however, because of resource and time restraints, this study could not provide the collaboration of a multicentered study. There is also a possibility of a selection bias because only patients who are able to participate in rehabilitation are admitted to inpatient rehabilitation facilities. Obese TBI patients have more complications during acute care hospitalization compared with nonobese patients and, as a result, may not be able to participate in rehabilitation.4 It is not known whether obese TBI patients were as likely as nonobese patients to be sent to rehabilitation from trauma centers. The effect of comorbidities was not investigated in this study because of lack of data for the vast majority of subjects. Analysis of comorbidities in both groups would examine levels of health among the sample group and determine whether the comorbidities have an effect on functional outcome. Lastly, a large number of patients were excluded because of lack of data on height and weight, which may bias the results.
CONCLUSIONS The findings of this study suggest that obesity had no adverse impact on motor functional outcomes of TBI patients who underwent inpatient rehabilitation. Hence, obesity should not be considered a hindrance in inpatient rehabilitation after TBI.
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ACKNOWLEDGMENTS
The authors thank Angela Welch, clinical system analyst of the Baylor Institute for Rehabilitation, for assistance in obtaining the necessary electronic records and Kelli R. Trungale, MLS, ELS, Baylor Scott & White Health, for editorial assistance. REFERENCES 1. Centers for Disease Control and Prevention: Adult obesity facts. Available at: http://www.cdc.gov/obesity/ data/adult.html. Accessed April 15, 2014 2. Stenson KW, Deutsch A, Heinemann AW, et al: Obesity and inpatient rehabilitation outcomes for patients with a traumatic spinal cord injury. Arch Phys Med Rehabil 2011;92:384Y90 3. Vincent HK, Seay AN, Vincent KR, et al: Effects of obesity on rehabilitation outcomes after orthopedic trauma. Am J Phys Med Rehabil 2012;91:1051Y9 4. Vincent HK, Vincent KR: Obesity and inpatient rehabilitation outcomes following knee arthroplasty: A multicenter study. Obesity 2008;16:130Y6 5. Brown CV, Rhee P, Neville AL, et al: Obesity and traumatic brain injury. J Trauma 2006;61:572Y6 6. Tagliaferri F, Compagnone C, Yoganandan N, et al: Traumatic brain injury after frontal crashes: Relationship with body mass index. J Trauma 2009; 66:727Y9 7. Centers for Disease Control and Prevention: Injury prevention & control: Traumatic brain injury. Available at: http://www.cdc.gov/TraumaticBrainInjury/data/ index.html. Accessed April 8, 2014 8. Mayo Clinic Staff: Traumatic brain injury. Available at: http://www.mayoclinic.com/health/traumatic-braininjury/DS00552/DSECTION=symptoms. Accessed April 8, 2014 9. Vincent HK, Weng JP, Vincent KR: Effect of obesity on inpatient rehabilitation outcomes after total hip arthroplasty. Obesity 2007;15:522Y30 10. National Institute on Disability and Rehabilitation Research: The Traumatic Brain Injury Model Systems. Available at: https://www.tbindsc.org/StaticFiles/ Documents/TBIModel%20SystemsBrochure2010.pdf. Accessed April 9, 2014 11. Centers for Disease Control and Prevention: About BMI for children and teens. Available at: http://www. cdc.gov/healthyweight/assessing/bmi/childrens_bmi/ about_childrens_bmi.html. Accessed June 7, 2014 12. DeCuypere M, Klimo P Jr: Spectrum of traumatic brain injury from mild to severe. Surg Clin North Am 2012;92:939Y57 13. Cournan M: Use of the Functional Independence Measure for outcomes measurement in acute inpatient rehabilitation. Rehabil Nurs 2011;36:111Y7 14. Centers for Disease Control and Prevention: About BMI for adults. Available at: http://www.cdc.gov/ healthyweight/assessing/bmi/adult_bmi/index.html. Accessed April 8, 2014
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