Assessment of the unmediated relationship between neurological impairment and health-related quality of life following spinal cord injury

Abstract

Objective: To assess the unmediated association between neurological impairment and quality of life (QoL) among persons with spinal cord injury (SCI), in the context of both early post-acute and long-term rehabilitation settings.

Design: An observational prospective cross-sectional study.

Setting: Two neurological rehabilitation centers, specializing in spinal cord injury, within a university hospital.

Methods: 156 adults with spinal cord injury in the early post-acute and chronic stages of rehabilitation.

Outcome Measures: Participants were categorized into tetraplegia or paraplegia groups based on neurological level of injury, and into complete or incomplete groups based on American Spinal Injury Association (ASIA) Impairment Scale (AIS) score. QoL was assessed by means of the World Health Organization Quality of Life Assessment-BREF (WHOQOL-BREF), Satisfaction with Life Scale (SWLS), Life Satisfaction Questionnaire (LISAT-9), and Personal Well-Being Index (PWI).

Results: WHOQOL-BREF and PWI predicted Level of Injury group classification and WHOQOL-BREF predicted Setting group classification. None of the questionnaires differentiated between the Type of Injury groups. At the early post-acute stage of rehabilitation, the QoL scores of participants with tetraplegia and paraplegia did not differ significantly, while significantly higher QoL scores were revealed in paraplegics in the long-term setting group.

Conclusions: A direct, unmediated effect of severity of neurological impairment was revealed with the WHOQOL-BREF, which distinguished between the tetraplegia and paraplegia groups, but not between the complete and incomplete injuries. QoL was significantly higher in paraplegia than in tetraplegia following the early post-acute stage of rehabilitation.

Introduction

Despite advances in our understanding of its pathogenesis, no curative treatment has been developed for spinal cord injury (SCI), which can leave survivors with significant residual impairment and permanent disability.¹ Residual impairments after neurological recovery depend on the initial severity of injury.

Rehabilitation aims to maximize level of functioning and quality of life (QoL) among SCI survivors, in accordance with the residual severity of their injuries.^2,3 As such, QoL is a key outcome measure in evaluating the effectiveness of rehabilitation programs.^4,5 While QoL is often used interchangeably with subjective well-being (SWB) in research and practice, the two terms are linked to different theoretical concepts. Both reflect person-centered approaches to assessing the subjective experience of “good life.” Rooted in a hedonistic philosophical view, SWB captures “experienced well-being,” through measures of positive affect, pleasure, and happiness, and their opposites: negative affect, misery, and distress.⁶ Meanwhile, subjective QoL was defined in 1994 by the World Health Organization (WHO) as follows:

An individual’s perception of their position in life, in the context of the culture and value system in which they live, and in relation to their goals, expectations, standards and concerns. It is a broad-ranging concept, incorporating in a complex way the person’s physical health, psychological state, level of independence, social relationships, personal beliefs, and salient features of the environment.⁷

This definition incorporates the concept of Eudaimonia, reflecting the view that a purposeful and worthwhile life is good. Subjective QoL includes health-related QoL (HRQoL), in adherence with the WHO and International Classification of Functioning, Disability and Health (ICF) models.⁸ In health care, HRQoL provides an assessment of how an individual's well-being might be affected over time by a disease, disability, or disorder.⁹

QoL has been shown to drop following SCI,^2,10 as a function of health and injury-related factors, age, sex, race, marital status, time since injury, educational level, mobility, environmental surroundings, work, and participation in various life domains.^11,12 Functional status, as defined by the ICF activity and participation domains, is considered an essential determinant of QoL.^2,3 However, the relationship between QoL and severity of neurological impairment remains controversial. Tate and Boschen et al.^13,14 did not find significant relationships between QoL and lesion-related factors (lesion level or completeness, time since injury, physical impairment, and medical complications). In contrast, a meta-analysis on 32 reports published from 1983 to 1992 suggested that severity of injury is negatively correlated with QoL, though the authors noted that definitive conclusions could not be drawn due to methodological limitations of the included studies.¹⁵ Variability in the approaches used to assess severity of impairment might also have contributed to these inconsistent results,^16–18 as suggested in meta-analyses on QoL following SCI.^19,20

Despite these inconsistencies, there is no ambiguity with regard to the strong negative correlation between QoL and measures of functional status, such as social engagement and ability to perform activities of daily living,²¹ which are in turn negatively impacted by the severity of neurological injury. It can therefore be assumed that impairment severity indirectly influences QoL, through its substantial impact on activity and participation.^11,22 In accordance, the current study investigated the unmediated association between neurological impairment and HRQoL among individuals with SCI, in the context of both early-subacute and long-term rehabilitation settings.

Methods

Participants and data collection

This study was conducted as part of a multi-center international development process for Core Sets following SCI in accordance with the ICF.²³

160 participants (40 participants in the early post-acute and long-term rehabilitation settings in each study center) were sequentially recruited from two departments specializing in post-SCI rehabilitation in Israel, and from the outpatient clinics of both hospitals. They were included if they had (a) sustained a SCI, (b) were at least 18 years old, and (c) could read and participate in an adequate level of conversation; and excluded if they had (a) prior diagnosis of a mental disorder, (b) sustained a severe traumatic head injury, or (c) other acquired or innate disabilities.

In accordance with the definitions used in the preliminary studies of the ‘ICF Core Set Development for Spinal Cord Injury (SCI)’ project, patients were recruited from the ‘early post-acute context’ and the ‘long-term context’.²³ The early post-acute context begins with active rehabilitation and ends upon completion of the first comprehensive rehabilitation period after the acute SCI. The long-term context follows the early post-acute context. This definition is considered internationally applicable, irrespective of different health systems.

The study was approved by the ethics committees at both medical centers. All participants were provided with written and verbal information about the study and signed an informed consent form.

Independent variables

All participants underwent a comprehensive assessment by a Board-certified physiatrist with extensive experience in the field of spinal cord injury, at each of the rehabilitation centers. Measures included in the ICF component of “body structure and function,” in relation to neurological impairment in SCI, were determined based on the clinical examination. Completeness or type of injury and level of injury were established based on the American Spinal Injury Association (ASIA) International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI).²⁴ Neurological level of injury (NLI) was determined according to the ISNCSCI, representing the most caudal segment of the cord with intact sensation and antigravity muscle function strength on both sides of the body.

Socio-demographic data (e.g. age, sex, years of education) and time since injury were also collected.

Dependent variables (QoL)

The World Health Organization Quality of Life Assessment-BREF (WHOQOL-BREF)²⁵ is a self-report questionnaire comprising five items selected from the more comprehensive WHOQOL to address overall QoL, satisfaction with health, daily activities, relationships, and living conditions. Each item is scored from 1 (very dissatisfied) to 5 (very satisfied). The WHOQOL-BREF was specifically developed for cross-cultural use and is available in 36 languages. It is widely used to assess perceived QoL and was selected for this study due to its excellent psychometric properties in many disability groups and its suitability for measurement of QoL in people with SCI. Its internal consistency ranged between .75 and .87. It has been used in different international WHO collaboration projects since 2002.

The Satisfaction with Life Scale (SWLS)²⁶ is a self-report measure of global life satisfaction. It comprises five items scored on a 7-point Likert scale, with ratings from 1 (strongly disagree) to 7 (strongly agree), which are summed to obtain a total score.²⁷ The SWLS is widely used in SCI research, especially in the United States. Its internal consistency ranges between .79 and .89 and several studies have confirmed its single factor structure.

The Life Satisfaction Questionnaire (LISAT-9)²⁸ is a measure of domain-specific life satisfaction. It comprises nine items, including one on general life satisfaction and eight domain-specific items (self-care, vocational situation, financial situation, leisure situation, sexual life, partner relations, family life, contact with friends). Responses are rated on a 6-point scale from “very dissatisfying” to “very satisfying” and scores are determined by averaging all items. The LISAT has been used to compare SCI samples from different countries (Sweden and Japan; China and UK; UK, Germany, Austria, and Switzerland).

The Personal Well-Being Index (PWI)²⁹ comprises seven items addressing satisfaction with specific life domains (standard of living, health, achieving in life, relationships, personal safety, community-connectedness, future security) and one optional item about overall life satisfaction. Responses are rated on a numeric scale from 0 “completely dissatisfied” to 10 “completely satisfied,” and summed to yield the total score. The PWI was developed in Australia for use in national surveys and has been adapted for international use. It has been designed as a unidimensional tool with internal consistency ranging between .70 and .85. In addition, it has been used in several published studies on SCI.^30,31

Data analysis

Neurological impairment was classified in relation to level (paraplegia vs. tetraplegia) and type (complete vs. incomplete) of injury. A multivariate analysis of variance (MANOVA) was conducted to compare the Level of Injury groups (paraplegia vs. tetraplegia) with respect to clinical and demographic data (e.g. age, years of education, time since injury), to ensure correct matching. Since the vast majority (93.5%) of participants had experienced traumatic SCI, the group was not divided and analyzed based on etiology. Another MANOVA was conducted to compare the groups with respect to questionnaire (WHOQOL-BREF, SWLS, LISAT, PWI) scores. Participants scoring two standard deviations above or below average scores on any questionnaire were omitted from analysis.

A binary logistic regression analysis was conducted to determine which questionnaire scores differentiated between groups based on Level of Injury (paraplegia vs. tetraplegia), Setting (inpatient vs. outpatient), and Type of Injury (complete vs. incomplete) most effectively. The dependent variable in this analysis was the measure used for classification, and the independent variables were the QoL questionnaires. The independent predictive values of the variables were expressed in odds ratios (ORs) with 95% confidence intervals (CI). P values of 0.05 or less were considered significant.

Finally, two 2-way analyses of variance (ANOVA) were conducted with (1) Setting and Level of Injury as independent variables and (2) Setting and Type of Injury as independent variables. The dependent variable was the questionnaire found to be most sensitive in the previous analyses. P values of 0.05 or less were considered significant.

Results

Of the 160 participants eligible for this study, 156 participants (128 males; mean age 45.62 years, SD = 15.75) met the inclusion criteria and could, thus, be included in the analysis. All participants had experienced SCI: 115 traumatic (74%), 8 (5%) non-traumatic, and 33 (21%) for which the data available was not sufficient to unequivocally determine etiology. No participants were excluded in this study for incomplete data acquisition, since full data were available in all QoL measures. The number of participants in each medical setting and injury is presented in Table 2.

Table 2. Participant and injury characteristics of the spinal cord injury cohort.

	Setting (early post-acute context/long-term context) 73/83	Level of injury (tetraplegia/paraplegia) 95/61	Type of injury (complete/incomplete)70/86
Age	42.12 (14.50)/46.06 (16.85)	47.95 (15.53)/44.12 (15.79)	43.63 (16.03)/47.23 (15.42)
Years of education	12.75 (3.99)/11.31 (3.43)	12.07 (3.82)/11.94 (3.74)	12.41 (3.27)/11.64 (4.1)
Time since injury (months)	3.26 (2.44)/140.17 (135.48)	63.45 (108.02)/73.37 (125.81)	73.46 (113.63)/62.34 (116.54)

WHOQOL-BREF and PWI predicted Level of Injury group classification and WHOQOL-BREF predicted Setting group classification at a significant level. None of the questionnaires differentiated between the Type of Injury groups (see Table 1).

Table 1. Summary of logistic regression analysis scores for all quality of life questionnaires.

	Percent correctly classified	Questionnaire	B (SE)	Wald χ2	OR
Level of injury	60.4	WHOQOL-BREF	−0.16 (0.07)	4.77*	0.84
		SWLS	−0.03 (0.04)	0.69	0.96
		LISAT-9	−0.69 (0.38)	3.32	0.49
		PWI	0.05 (0.02)	4.08*	1.05
Setting	58.4	WHOQOL-BREF	−0.15 (0.07)	4.43*	0.89
		SWLS	0.03 (0.04)	0.76	1.03
		LISAT-9	0.31 (0.36)	0.72	0.77
		PWI	−0.003 (0.02)	0.01	1.01
Type of injury	57.4	WHOQOL-BREF	−0.11 (0.07)	2.44	0.85
		SWLS	0.03 (0.04)	0.6	1.03
		LISAT-9	−0.25 (0.37)	0.45	1.36
		PWI	0.01 (0.02)	0.37	0.99

Note: WHOQOL-BREF = World Health Organization Quality of Life Assessment-Brief, LISAT-9 = Life Satisfaction Questionnaire, PWI = Personal Well-Being Index, SWLS = Satisfaction with Life Scale, SE = standard error, OR = odds ratio, *P < 0.05.

In accordance with these results, Type of Injury was omitted from further analysis, while Level of Injury was included. Between-group comparisons with respect to Level of Injury across demographic, clinical, and questionnaire data produced non-significant results, F(1,156) = 0.75, P = 0.52, partial η² = .01 (see Table 2).

Comparisons of the two Level of Injury groups with respect to the questionnaires were significant F(1,149) = 3.31, P = .03, partial η² = .08. All QoL questionnaire scores were higher in the paraplegia group than in the tetraplegia group except the PWI, for which the between-group difference was not significant (see Figure 1).

Figure 1.

Comparison between paraplegia and tetraplegia groups with respect to scores on quality of life questionnaires. Note: WHOQOL-BREF = World Health Organization Quality of Life Assessment-Brief, LISAT-9 = Life Satisfaction Questionnaire, PWI = Personal Well-Being Index, SWLS = Satisfaction with Life Scale. *p < 0.05.

In accordance with these results, we used the WHOQOL-BREF as the sole QoL measure, as it was found to have the best discrimination capacity and therefore the highest predictive value.

The two-way Setting x Level of Injury ANOVA yielded a significant model, F(3,154) = 5.27, P = .002, partial η2 = .09. The main effect of Setting was significant, F(1,154) = 6.3, P = .01, partial η² = .04, showing that the inpatient group (M = 16.8, SD = 4.03) reported higher QoL than the outpatient group (M = 15.46, SD = 3.68). Another main effect was found for Level of Injury, F(1,154) = 5.02, P = .02, partial η² = .03, showing that the paraplegia group (M = 16.73, SD = 3.87) reported higher QoL than the tetraplegia group (M = 15.14, SD = 3.77).

Setting and Level of Injury were also found to interact, F(1,154) = 4.87, P = .02, partial η² = .03. An independent sample t-test was significant t(1,78) = 3.57, P < .01, revealing that participants with paraplegia in the inpatient setting (M = 16.82, SD = 4.08) reported better QoL than participants with tetraplegia in the outpatient setting (M = 13.85, SD = 3.04) (see Figure 2).

Figure 2.

WHOQOL-BREF scores by Setting and Level of Injury classifications. Note: WHOQOL-BREF = World Health Organization Quality of Life Assessment-Brief.

An independent samples t-test revealed that the QoL results of the paraplegia and tetraplegia groups within the inpatient setting did not differ significantly, t(1,71) = .04, P = .87, (M = 16.82, SD = 4.08), while within the outpatient setting, the paraplegia group reported better quality of life than the tetraplegia group t(1,78) = 3.57, P < .01, (M = 13.85, SD = 3.04) (see Figure 2).

Finally, the two-way Setting x Type of Injury ANOVA yielded a significant model, F(1,146) = 2.91, P = .03, partial η2 = .05. However, there were no significant main effects of Setting, F(1,146) = 3.36, P = .06, or Type of Injury F(1,146) = .94, P = .33, and there was no interaction F(1,146) = 3.06, P = .08.

Discussion

In this study, we compared four QoL assessment instruments in their ability to differentiate between groups based on two measures of neurological impairment in patients with SCI, completeness and level of injury. Improving QoL, a key outcome measure in this population, is a major clinical goal. As healthcare steadily improves, more people survive SCIs and must live with disabilities for longer. Independence, self-esteem, and living without suffering are explicitly defined components of QoL in the SCI population.³² In accordance with the aims of this study, there is increasing interest in examining factors that can potentially enhance QoL within the context of medical and rehabilitative care.³³

SCI-related impairments involve multiple body functions and structures (e.g. cardio-vascular, muscles, bones, bladder and bowel functions) caused by direct damage to neural structures within the spinal cord.³⁴ As a result, SCI survivors experience limitations in performing daily living and social activities, which negatively impact QoL.²¹ To date, the contribution of each domain of the ICF (body function/structure, activity and participation) to QoL is not well-established. On these grounds, we aimed to characterize the unmediated relationship between specific characteristics of neurological impairment (body function/structure) and diminished well-being among survivors.

Our study showed that the WHOQOL-BREF distinguished between the tetraplegia and paraplegia groups, but not the type of injury groups. This finding contrasts with Kivisild et al.’s³⁵ assumption that the ASIA Impairment Scale (AIS) can be a significant predictor of QoL, as measured by the Medical Outcome Study 36-item short-form health status survey (RAND-36-item health survey 1.0). Also in contrast with the current findings, Ebrahimzadeh et al.³⁶ and Rognoni et al.³⁷ found no association between injury level and QoL as assessed using the SF-36 QoL questionnaire. Jain et al.¹² however, did demonstrate that higher injury level, resulting in decreased overall muscle strength and more severe muscle loss, was associated with lower QoL scores.

Some researchers^20,38,39 have proposed that these conflicting results were caused, at least partially, by differences in the instruments used to asses QoL. HRQoL is used in the medical literature to assess QoL when health status is affected, especially due to chronic impairments that lead to disability. It is a multidimensional construct that incorporates objective measures of QoL alongside measures of subjective well-being (SWB), which involve feelings and cognitive judgements about the “goodness” of life as a whole. As such, SWB is strongly associated with aspects of mental health such as anxiety and depression and to a lesser extent with factors impacting physical health.^40,41 There is some disagreement regarding which, and to what extent, specific domains of HRQoL are associated with SWB, and regarding the direction of causality in this relationship. It is commonly accepted that HRQoL influences SWB while the reverse relationship does not hold. However, the influence of SWB on the social dimension of HRQoL is still to be determined.⁴²

In the current study, only the WHOQOL-BREF was found to discriminate adequately between the inpatient and chronic SCI groups. This questionnaire stands out in its inclusion of social relationship and environment domains alongside physical and psychological health. Skevington et al.⁴³ showed good discriminant validity for all its domains.

We also revealed a significant interaction between rehabilitation setting (inpatient vs. outpatient) and level of neurological impairment in relation to QoL. Overall, the QoL of SCI participants during early post-acute (inpatient) rehabilitation was higher than that in the long-term context (chronic) participants. Interestingly, participants in the paraplegic group showed significant higher QoL scores compared to the tetraplegic group uniquely in the chronic setting. This finding might be explained by health-related factors such as fatigue,⁴⁴ orthostatic hypotension, or pressure injuries, which are more likely to occur in tetraplegia in the long-term rehabilitation context. All these factors are known to occur in both groups during the early post-acute stage of rehabilitation, and to wear off with time in individuals with paraplegia. Tate et al.¹³ suggested that QoL holds steady at first but declines in later years. However, Westgren and Levi⁴⁵ claimed that individuals with SCI are more likely to report good QoL the longer they have had their injuries. Kreuter et al.⁴⁶ also reported a positive correlation between time from lesion and QoL scores in a group of Swedish patients with SCI. In these studies, emotional and mental health were also found to improve with time, influencing QoL

Study limitations

Our ability to generalize the current study findings is limited due to the sampling procedure, as only SCI participants who voluntarily showed up for outpatient follow-up were included in the chronic group. These patients were more likely to exhibit medical complications that could unidirectionally influence HRQoL. Furthermore, due to its cross-sectional design, the study could not unequivocally support causal relationships between the variables. Future longitudinal studies should be conducted using modeling analysis (e.g. path analysis) to examine distinct causal relationships.

Conclusions

HRQoL reflects the ability of survivors to cope with and adapt to the medical and social consequences of SCI. It is imperative to address this concern, as the majority of survivors now have life expectancies approaching those of the general population. As such, we aimed to examine the strength of the interaction between neurological impairment and the four most frequently used QoL instruments, in Israeli individuals with SCI in two clinical settings. To our knowledge, no previous study has compared these instruments under such conditions. Completeness and level of injury were the major factors associated with severity of neurological impairment.

The WHOQOL-BREF was the only QoL measure associated with level of injury, though not with type of injury. A direct, unmediated effect of severity of neurological impairment was revealed with the WHOQOL-BREF, which distinguished between tetraplegia and paraplegia groups, but not between complete and incomplete injuries. The process of post-injury adaptation appears to have been more powerful in participants with paraplegia, as their QoL scores were higher after discharge in comparison to those with tetraplegia, unlike in the early post-acute rehabilitation setting. To our knowledge, this is the first investigation demonstrating the unmediated role of injury severity in determining QoL among individuals with SCI.

Abbreviations

AIS – American Spinal Injury Association Impairment Scale

ASIA – American Spinal Injury Association

HRQoL – health-related quality of life

ICF – International Classification of Functioning, Disability and Health

ISNCSCI – International Standards for Neurological Classification of Spinal Cord Injury

LISAT-9 – Life Satisfaction Questionnaire

NLI – neurological level of injury

QoL – quality of life

PWI – Personal Well-Being Index

SCI – spinal cord injury

SWB – subjective well-being

SWLS – Satisfaction with Life Scale

WHO – World Health Organization

WHOQOL-BREF – World Health Organization Quality of Life Assessment-BREF

Disclaimer statements

Contributors None.

Funding None.

Conflicts of interest Authors have no conflict of interest to declare.