University of Groningen
Outcomes after Spinal Cord Injury
Osterthun, Rutger
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Publication date: 2018
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Osterthun, R. (2018). Outcomes after Spinal Cord Injury. Rijksuniversiteit Groningen.
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6
Physical capacity in relation to
participation in persons with
long-standing spinal cord injury
Rutger Osterthun, MD1,2,3, Elisabeth J van Overbeeke, MD4, Floris
WA van Asbeck, MD, PhD4, Jacinthe JE Adriaansen MD, PhD4,
Casper F van Koppenhagen, MD, PhD5, Sonja de Groot, PhD6,7,
Ilse JW van Nes, MD, PhD8, Marcel WM Post, PhD2,4
1 Jeroen Bosch Hospital, Tolbrug Rehabilitation Centre, ‘s Hertogenbosch, the Netherlands 2 University of Groningen, University Medical Center Groningen, Department of Rehabilitation
Medicine, Groningen, the Netherlands
3 Rijndam Rehabilitation, Rotterdam, the Netherlands 4 Center of Excellence in Rehabilitation Medicine, Brain Center Rudolf Magnus, University
Medical Center Utrecht and De Hoogstraat Rehabilitation, Utrecht, the Netherlands
5 Department of Rehabilitation, Physical Therapy Sciences and Sports, Brain Center Rudolf
Magnus, University Medical Center Utrecht, Utrecht, the Netherlands
6 Amsterdam Rehabilitation Research Center, Reade, Amsterdam, the Netherlands 7 University of Groningen, University Medical Center Groningen, Center for Human Movement
Sciences, Groningen, the Netherlands
8 Department of Rehabilitation, Sint Maartenskliniek, Nijmegen, the Netherlands
aBSTRaCT
Objective: To study the relationship between physical capacity and participation in
persons with long-standing spinal cord injury (SCI).
design: Cross-sectional study. Setting: Community.
Participants: 244 persons with a long-standing SCI. Inclusion criteria were: time since
injury (TSI) ≥10 years, age at injury between 18 and 35 years, current age between 28 and 65 years and wheelchair dependency.
Interventions: Not applicable.
main outcome measures: Participation was measured with the Restrictions subscale of
the Utrecht Scale for Evaluation of Rehabilitation-Participation (USER-P). Peak power output (POpeak) was measured with a graded peak wheelchair exercise test. Informa-tion on demographics, cause and severity of injury, mental health and secondary health conditions (SHCs) was gathered by a self-report questionnaire and an extensive medical assessment by the rehabilitation physician.
Results: 150 of the 244 included participants performed the exercise test. Persons who
did not participate in the exercise test were older, had a longer TSI, had more often a tetraplegia, were lower educated, had more frequently four or more SHCs and had lower functional independence and participation scores. Univariable linear regression analysis showed a significant relation between POpeak and participation (beta 0.429, p<0.001). A multivariable linear regression model showed that POpeak was also related to participation (beta 0.272, p=0.001) when controlled for functional independence. In this model, POpeak explained an additional 7.5% of the variance of the Restriction scale of the USER-P.
Conclusion: A higher physical capacity was independently related to better
INTROduCTION
Since survival and medical care after spinal cord injury (SCI) have considerably improved, optimizing the participation level has become one of the main goals of rehabilitation after a SCI, especially in the outpatient clinic.1,2 Participation may be
defined as the involvement of an individual in a life situation and represents the social perspective on functioning.3 Participation levels among persons with SCI are
in general lower than among non-disabled persons.4-12 Different approaches may be
used to describe participation after SCI.4 Objective participation is society-perceived
participation, based on social standard judged against the impact of chronic health conditions in different populations.4 Subjective participation takes the person’s
experi-ence regarding participation into account.4 Several determinants of participation have
been described, such as severity of the injury, age (both at injury as at the time of the study), educational level, functional independence, wheelchair skills, self-efficacy and purpose in life.4,6,7,9,13 Furthermore, hospitalization due to secondary health conditions
(SHCs) may lead to lower participation levels.14 Maintaining participation levels may
thus be an important issue for persons aging with their SCI.
It is often assumed that a higher physical capacity is beneficial for participation. The relation between physical capacity and participation is especially interesting since physical capacity is a modifiable factor. Physical capacity may be defined as the combined ability of the cardiovascular, respiratory and neuro-musculoskeletal systems to attain a certain level of fitness.15 The combination of physical disabilities, loss of
autonomic control and changes in metabolic, pulmonary and vascular functions may lead to a diminished physical capacity after SCI. Due to a sedentary lifestyle, physical capacity may further decrease.15-18 In the literature, physical capacity is commonly
expressed as peak oxygen uptake (VO2peak) and peak power output (POpeak). Although the VO2peak is considered a useful measure for physical fitness in SCI, the POpeak is more informative of the actual capacity to propel a hand-rim wheelchair, as the POpeak is also determined by, among others, mechanical efficiency and wheelchair propulsion skills.19
It has been shown that better physical capacity is related to better health, performing activities and quality of life.20-23 Little is known, however, on the relation between
physical capacity and participation. Manns et al. found no relation between VO2peak and overall participation levels.24 Van Velzen et al. examined the influence of physical
capacity on returning to work five years after SCI in a prospective cohort. They found that a higher POpeak resulted in a higher percentage of persons returning to work.25
Since little is known on the relation between physical capacity and participation, the purpose of our study was to investigate the relationship between physical capacity and participation in persons with long-standing SCI controlling for demographics, injury
characteristics, SHCs, mental health and functional independence. We hypothesized that persons with a better physical capacity would have significantly higher participation levels.
mEThOdS
design
Data for this study was derived from the ‘Active LifestyLe Rehabilitation Interventions in aging Spinal Cord injury’ (ALLRISC) study, a cross-sectional study performed in eight rehabilitation centers with SCI rehabilitation in the Netherlands.26,27
Participants
Inclusion criteria of the ALLRISC study were: SCI with a time since injury (TSI) of at least 10 years, age at injury between 18 and 35 years, current age between 28 and 65 years and wheelchair dependency (at least for longer distances). Participants were excluded if their mastery of the Dutch language to understand questionnaires and test instructions was insufficient. All participants signed informed consent before participating.27
For the purpose of this study, participants were excluded if information on participation levels was missing, or if POpeak values of participants who performed the exercise test were missing.
Procedure
Participants were invited for a one-day visit to one of the eight participating rehabilitation centers. This day included an aftercare check-up by the SCI rehabilitation physician and an oral interview and physical tests by a trained research assistant, including a graded peak wheelchair exercise test. Participants were also asked to complete a questionnaire before the visit to the rehabilitation center. The study protocol was approved by the Medical Ethics Committee of the University Medical Centre Utrecht.27
Instruments
Participation
The Restrictions scale of the Utrecht Scale for Evaluation of Rehabilitation-Participation (USER-P) was used to measure participation. The USER-P is a self-report questionnaire, which contains three scales, namely Frequency, Restrictions and Satisfaction. The Restrictions Scale of the USER-P has been shown to be the most valid and responsive scale of the USER-P.2,28,29
The 11 items of the Restrictions subscale are scored on a 4-point scale, ranging from not possible at all to no difficulty at all. There is a “not applicable” option,
if the item is not relevant to the participant or the experienced restrictions are not related to the participant’s health status or disability. The scale score is the sum of the item scores, converted to a 0 – 100 scale. Higher scores indicate better levels of participation (less restrictions).30 The USER-P covers chapters 6 to 9 of the International
Classification of Functioning, Disability and Health (ICF), which are most characteristic for participation.31
Physical capacity
A graded peak wheelchair exercise test on a motor-driven treadmill was used to test the physical capacity, which was measured by POpeak (Watt). The protocol of the test is described in more detail by Dallmeijer et al.32 and is used in multiple studies
for examining physical capacity.15,25,33-35 During the test there was a 0.36° increase in
treadmill inclination per minute. The POpeak was determined from the product of drag force measured during a separate wheelchair drag test and the treadmill belt velocity during the exercise test. POpeak was defined as the power output corresponding to the highest slope of the treadmill, which was maintained for at least half a minute.
Demographics
Information on age, gender and level of education was gathered with the questionnaire. Participants who completed high school were arranged in the ‘high level of education’ group, others were arranged in the ‘low level of education’ group.
Injury characteristics
During the visit to the rehabilitation center, participants were neurologically examined by the rehabilitation physician. The SCI was characterized according to the International Standards for the Neurological Classification of Spinal Cord Injury (ISNCSCI).36
Ameri-can Spinal Injury Association (ASIA) Impairment Scale (AIS) A and B were considered motor complete, AIS C and D motor incomplete. Levels of injury C1-C8 were defined as tetraplegia, levels below C8 as paraplegia.
Secondary health conditions
As part of the structured interview, the rehabilitation physician asked whether partici-pants had suffered from hypotension, pneumonia, autonomic dysreflexia (AD), pressure ulcers, problematic spasticity, urinary tract infections (UTI), musculoskeletal pain and neuropathic pain in the last 3 months. Also the presence of neurogenic heterotopic ossification (NHO) was recorded. Each SHC was scored as present (1) or absent (0) and a sum-score of the number of SHCs (0-9) was calculated
Hypotension was checked for by the assessment of symptoms (e.g. light-headedness or fainting).
Pneumonia was defined as an infection of the lower respiratory tract treated with antibiotics.
AD was defined as a sudden reaction of the autonomic nervous system triggered by a stimulus below the level of the lesion, causing an increase in blood pressure accompa-nied by other symptoms as pallor, piloerections, cold extremities and profuse sweating below the level of the lesion, and severe headaches, flushing of the skin, bradycardia and nasal congestion above the injury level.
Pressure ulcers were defined as category I, II, III or IV according to the classification of European Pressure Ulcer Advisory Panel (EPUAP).37
Problematic spasticity was scored when a participant indicated that spasticity was pres-ent and that it interfered moderately or extensively with activities in daily life.
UTI was defined as a symptomatic infection of the urinary tract treated with antibiotics, and the presence of one or more of the following characteristics: increased spasticity, malaise, onset of urinary incontinence, gritty particles or mucus in the urine or cloudy urine with increased odor, AD, discomfort or pain during urination.
Neuropathic pain was defined as at-level or below-level pain, originating from syringo-myelia, spinal cord ischemia or trauma.38
Musculoskeletal pain was defined as nociceptive pain originating from bone, joint or muscle trauma or overuse.39
NHO was defined as the presence of bone in soft tissue surrounding paralyzed joints, confirmed by radiological examination.
Functional independence
The Spinal Cord Independence Measure (SCIM) III was administered during an oral in-terview by the research assistant. The SCIM III is designed to measure the performance of activities of daily living in persons with SCI. The SCIM III consists of three subscales: self-care, respiration and sphincter management, and mobility, with a total score rang-ing from 0 to 100, a higher score indicatrang-ing more independency.40,41
Mental health
Mental health was measured with the Mental Health Inventory-5 (MHI-5), which con-sists of five questions on mood. A sum-score was calculated and converted to a 0 – 100 scale. Higher scores indicate a better mental health.42
Statistical analysis
Descriptive statistics were calculated. Mann-Whitney U and Chi-square tests were used to analyze the differences in participation scores between participants who did and did not participate in the graded peak wheelchair exercise test.
USER-P Restriction scale scores were analyzed for persons with a high and low POpeak, based on the median of POpeak, and tested for differences with Mann-Whitney U tests. For these analyses, persons with a paraplegia and tetraplegia were separately analyzed and cut-off points for high or low POpeak were thus separately established for these subgroups.
The association between physical capacity (POpeak) and participation (USER-P Restrictions scale), corrected for possible confounding factors (demographics, injury characteristics, mental health, functional independence and the SHC sum-score), was studied with linear regression analyses. Within these analyses, POpeak was the independent variable and the USER-P Restrictions scale the dependent variable. First, an univariable regression analysis for the relation between POpeak and participation was performed. Second, a multivariable linear regression analysis was performed for this relation. In these analyses, possible confounders were added one by one and only confounders that changed the regression coefficient B of POpeak with ≥10% were included in the final model. Within the multivariable regression analysis, the squared partial correlation was calculated to determine the unique explained variance of POpeak. All analyses were performed using SPSS 21.0 for windows (IBM; Armonck NY).
RESulTS
descriptives
Between November 2011 and February 2014, 566 persons were invited of whom 282 participated in ALLRISC. For the purpose of this study, 19 participants were excluded as information on participation levels was missing. Further, 19 participants who performed the exercise test were excluded as POpeak values were missing (nearly all due to defect force transducers).
A total of 150 of 244 included participants performed the graded peak wheelchair exercise test. Most frequent reasons for not performing the test were either health-related, like having a high blood pressure or shoulder problems, or the use of a power wheelchair. Characteristics of persons who did and who did not perform the exercise test are displayed in Table 1 to get an impression of differences between these groups. The median POpeak was 50.8 Watt (IQR 33.3-69.1). Persons who did not participate in the exercise test were older, had a longer TSI, had more often a tetraplegia, were lower educated and had more frequently four or more SHCs. Further, they had lower functional independence and participation scores than persons who did participate in the exercise test.
Relation between physical capacity and participation
Scores of the USER-P Restriction scale are displayed in Table 2 for persons with a high and low POpeak. Those with a low POpeak showed significantly lower participation scores in both persons with tetraplegia and paraplegia.
Univariable linear regression analysis showed a significant relation between POpeak and participation (Table 3). The final multivariable linear regression model showed that POpeak was related to participation when controlled for confounders (Table 3). In this model, POpeak explained 7.5% of the variance of the restriction scale of the USER-P. Functional independence was the only confounder.
Table 1. Characteristics of participants and non-participants of the exercise test Total (N=244) No exercise test (n=94) Exercise test (n=150)
median (IQR) median (IQR) median (IQR)
mann-Whitney u p
Age (years) 48.0 (42.4-55.1) 50.7 (44.7-58.0) 46.3 (40.6-53.9) -3.3 0.001
TSI (years) 22.5 (17.0-31.0) 25.0 (19.0-34.0) 21.0 (16.0-29.0) -3.1 0.002
Functional independence (SCIM) 64.0 (39.3-68.0) 37.0 (25.0-66.0) 66.0 (60.0-69.0) -5.9 <0.001 Mental health (MHI-5) 76.0 (64.0-88.0) 76.0 (64.0-84.0) 76.0 (66.0-88.0) -0.9 0.395 USER-P – Restrictions scale 78.8 (63.4-93.3) 66.7 (51.5-79.4) 86.7 (72.7-96.7) -6.8 <0.001
frequency N (%) frequency n (%) frequency n (%) Chi-square p Gender (male) 181 (74.2) 71 (75.5) 110 (73.3) 0.1 0.703
Level of education (high) 172 (70.5) 52 (55.3) 120 (80.0) 16.9 <0.001
Lesion type (complete) 201 (82.4) 78 (83.0) 123 (82.0) 0.04 0.845
Level of injury (tetraplegia) 100 (41.2) 59 (63.4) 41 (27.3) 30.9 <0.001
SHC sum-score (≥4) 80 (32.8) 39 (41.5) 41 (27.3) 5.3 0.022
Abbreviations; MHI-5: Mental Health Inventory-5; SHC: secondary health condition; SCIM: Spinal Cord Independence Measure III; TSI: time since injury; USER-P: Utrecht Scale for Evaluation of Rehabilitation-Participation; IQR: interquartile range
Table 2. USER-P Restriction Scores for persons with a high and low POpeak, separately for persons
with a paraplegia and tetraplegia
Paraplegia (n=109) Tetraplegia (n=41)
Median (IQR)
Mann-Whitney U
p Median (IQR)
Mann-Whitney U p
Low POpeak 81.5 (70.4-93.3) 892.5 <0.001 66.7 (52.1-84.2) 103.0 0.005
dISCuSSION
In this cross-sectional study we found that a higher physical capacity was related to better participation levels in persons with a long-standing SCI after controlling for func-tional independence, which turned out to be the only confounder. POpeak explained 7.5% of the variance of the Restriction scale of the USER-P.
The median values of physical capacity found in our study correspond with values found among persons with SCI who used a wheelchair measured 5 years after discharge from first inpatient rehabilitation.21,25 A review and a secondary analysis of five
studies examining physical capacity in persons with SCI found higher POpeak scores. However, both studies also included athletes and the participants of those studies were considerably younger and in general had a shorter TSI.43,44
Our main result that POpeak is related to participation roughly corresponds with the existing literature. Three studies have been performed with similar objectives, but different methodologies. In a longitudinal cohort study, an association was found between POpeak, but not VO2peak, with return to work at one and at five years after the injury.25,45
In a cross-sectional study, no correlations were found between participation levels and fitness (VO2peak, determined by arm-crank ergometry) in 38 persons with long-standing SCI, except for one correlation between VO2peak and the physical independence aspect of handicap in the subgroup of persons with paraplegia. POpeak was not analyzed in that study.24 Our study therefore provides new clues for the importance of good physical
capacity for maintaining participation. An intervention study would, however, be necessary to show the impact of improving physical capacity on participation.
Some methodological considerations should be taken into account when considering the results of our study. Firstly, participation is a complex concept with several dimensions. The USER-P Restrictions subscale is a subjective measure of the experienced restrictions in participation, which is hard to compare with objective measures, such as the CHART.46 A consequence of using a subjective measure of participation may be that
Table 3. Univariable and multivariable linear regression analyses with USER-P Restrictions subscale
as dependent variable, POpeak (W) as independent variable and functional independence as confounder (N=150) Determinant B (SD) Beta T P Univariable Constant POpeak 68.388 (2.747) 0.269 (0.047) 0.429 5.8 <0.001 Multivariable Constant POpeak 45.216 (5.933) 0.170 (0.050) 0.272 3.4 0.001 Functional independence 0.455 (0.105) 0.346 4.3 <0.001
the outcomes may be blurred by mental health conditions such as a depressed mood. Our results did however not confirm a confounding effect of mental health.
Secondly, in general, POpeak and VO2peak are measures that are both used to describe physical capacity after SCI. In a study performed with the same data, a strong correlation has been described between POpeak and VO2peak (pearson r=0.86).47 For
the purpose of this study we have decided to use POpeak for the analyses since POpeak is a more functional measure of physical capacity.19
Thirdly, a wheelchair exercise test, as used in our study, may be closer related to daily wheelchair related activities than an arm-crank ergometry test.
Finally, considering the ICF model, the relation between physical capacity and participation may be more complex than stated in the hypothesis of this study. Although we had hypothesized that a better physical capacity would be beneficial for participation, higher participation levels may in turn also lead to a better physical capacity. Furthermore, in the conceptual model used in this study, functional independence (SCIM III) is considered as a confounder of the relation between physical capacity and participation. Higher participation levels of persons with a better physical capacity may partly be directly the result of better functional independence levels. However, even when corrected for the SCIM III, there was a relation between the physical capacity and participation.
Concerning the clinical relevance of this study, the results suggest that improving physical capacity could lead to better participation levels in this diagnostic group. For example, Bougenot et al. found that a six week interval-training programme of 45 minutes training for three times a week improved the maximal tolerated power (the highest load that could be maintained for one minute) with 14.4 Watts in a wheelchair exercise test.48 Using the regression coefficient of our univariable regression analysis,
an increase of PO peak with 14.4 Watts would correspond with a better performance of 1.3 point on one of the 4-point scale USER-P Restriction Scale items. Of course, an intervention design would be necessary to draw conclusions on this subject. Nevertheless, considering the importance of participation, the results of our study may thus be of relevance for persons with a SCI. Another study found that fatigue and decreased muscle strength were negatively affecting participation in exercise, particularly for those who lived 36-55 years after SCI.49 A decrease of the physical
capacity could thereby possibly lead to a downward spiral.
Remarkably, the level and completeness of the injury did not confound the relation between physical capacity and participation. This may be the result of including mainly persons with a paraplegia and persons with AIS A, B and C. This is also reflected by the small interquartile range of the functional independence (SCIM III) scores in this group. And although the presence of SHCs was asked during a thorough structured interview, limited information was gathered on the severity of SHCs. This may be important
information considering our hypothesis. Finally, age may become a confounder when analyzing persons older than 65 years.
Study limitations
Several methodological aspects have subsequently resulted in a the selection of a group of better functioning persons with SCI. Due to the cross-sectional study design and inclusion of participants with a long TSI there may have been a survivor effect, meaning that healthier persons may have been more available to participate in the study. Within the included study population, the group of persons that was finally analyzed was clearly the better functioning group. It is likely that the physical capacity of the group who did not perform the exercise test would have been lower. It is unclear to what extent the relation between physical capacity and participation would be influenced if it would be possible to analyze this group. Considering generalization of the results, the analyzed participants were in general younger, had more often a complete SCI and a paraplegia than persons with SCI admitted to Dutch and Flemish rehabilitation centres.50
Due to the inclusion criteria, the results are applicable to a group of wheelchair-dependent persons with long-standing SCI aged under 65 years.
Clinical implications
Besides the known benefits of a good physical capacity, this study provides clues for another beneficial effect of a good physical capacity for persons with SCI, namely a better participation level. Especially since persons with a SCI tend to have an inactive lifestyle, paying attention to improving the physical capacity during rehabilitation and afterwards is important as it may improve or maintain participation levels.
Conclusions
A higher POpeak was related to better participation levels in persons with a long-standing SCI after controlling for functional independence, which turned out to be the only confounder. The results suggest that improving the physical capacity may lead to higher participation levels. An intervention study would be necessary to confirm this.
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