SPINAL CORD INJURY (SCI) commonly has a major

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1 ORIGINAL ARTICLE Impact of Fatigue on the Health-Related Quality of Life in Persons With Spinal Cord Injury Nirupama Wijesuriya, BMedSc, Yvonne Tran, PhD, James Middleton, PhD, Ashley Craig, PhD ABSTRACT. Wijesuriya N, Tran Y, Middleton J, Craig A. Impact of fatigue on the health-related quality of life in persons with spinal cord injury. Arch Phys Med Rehabil 2012;93: Objective: To study the impact of fatigue on health-related quality of life (HR-QOL) associated with spinal cord injury (SCI). Design: Matched group design with several independent measures. Setting: University-based laboratory. Participants: Persons with SCI (n 41) and an average 16.5 years duration of community living with SCI and a group of able-bodied controls (n 41) with similar sex ratio, age, and level of education. Participants with SCI were enrolled through rehabilitation unit contacts and through advertising in newsletters. Interventions: Not applicable. Main Outcome Measures: The main independent measures reported in this article include the Iowa Fatigue Scale and the Medical Outcomes Study 36-Item Short-Form Health Survey. Results: As expected, persons with SCI were found to have significantly lower HR-QOL. Fatigue was found to be more prevalent in the SCI group, and was associated with lower HR-QOL in both groups. Factorial analysis of variance indicated significant interactions in which persons with SCI with low fatigue levels had similar HR-QOL to the able-bodied controls regardless of their fatigue level, while persons with SCI with elevated fatigue had significantly reduced HR-QOL. Factors such as age, education, completeness and level of lesion, and community integration were not associated with increased fatigue levels. However, a shorter time since injury was found to be significantly associated with higher levels of fatigue. Conclusions: The Iowa Fatigue Scale data suggest over 50% of the SCI group had elevated fatigue, which was associated with significantly reduced HR-QOL. Research is needed that identifies factors that raise vulnerability to fatigue, and strategies designed to address the negative impacts of fatigue need to be evaluated. Key Words: Fatigue; Quality of life; Rehabilitation; Spinal cord injuries by the American Congress of Rehabilitation Medicine 319 SPINAL CORD INJURY (SCI) commonly has a major negative impact on activities, participation, and level of independence due to loss of motor and sensory function. 1,2 Furthermore, bladder and bowel dysfunction, chronic pain, and depressive mood are some of the prevalent secondary conditions that can act to decrease well-being in people with SCI even further. 1-9 Long-term prevalence rates for secondary conditions range from around 60% for chronic pain to 40% for depressive mood. 8,9 It has been shown that factors like chronic pain and a negative mindset can act independently to decrease well-being significantly, well beyond the negative impact expected from the primary burden of a SCI. 3 Others have found that well-being is directly and indirectly impacted by factors such as age, physical health, disability problems, perceptions of aging, and neuropathic pain. 10,11 Health-related quality of life (HR-QOL) measures have become recognized as important outcome measures when assessing the well-being of people with SCI, and they complement physical assessments such as extent of impairment and activity limitation. 12 While concepts of quality of life (QOL) vary, there is agreement that QOL is a construct involving both subjective and objective assessment of a range of life domains. 1 Some QOL measures assess health from a multidimensional perspective including physical, psychological, social, and vocational aspects. 2,13-15 The HR-QOL instrument employed in the research reported in this article, the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), provides a measure of QOL based on participants judgments about their own health and life status. 1,3 The SF-36 was used in this study as it has been shown to be a reliable and valid measure of HR-QOL and has been frequently used to investigate the impact of disease on well-being. 1,16 Research with the SF-36 has repeatedly demonstrated clinically significant lower QOL in domains such as physical health and activity in persons with SCI, especially for factors such as negative mood, spasticity, socioeconomic disadvantage, and medical complications. 1,3,7,17-19 Additionally, research has also shown that HR-QOL in people with SCI is substantially influenced by attitudinal factors like selfefficacy rather than just disability-related factors such as completeness or level of the lesion. 3,20,21 For the purposes of the research reported in this article, fatigue was defined as a state of chronic tiredness and pervasive feeling of exhaustion This definition implies an important distinction between the temporary state of feeling tired after a From the Rehabilitation Studies Unit, Sydney Medical School, The University of Sydney (Wijesuriya, Tran, Middleton, Craig); and the Royal Rehabilitation Centre (Middleton); Sydney, NSW, Australia. Supported by the Australian Research Council (grant no. LP ). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated. Reprint requests to Ashley Craig, PhD, Rehabilitation Studies Unit, Sydney Medical School, The University of Sydney, Ryde, NSW, Australia, 1680, a.craig@sydney.edu.au /12/ $36.00/0 doi: /j.apmr ANOVA CIQ HR-QOL QOL SCI SF-36 TBI List of Abbreviations analysis of variance Community Integration Questionnaire health-related quality of life quality of life spinal cord injury Medical Outcomes Study 36-Item Short-Form Health Survey traumatic brain injury

2 320 FATIGUE ASSOCIATED WITH SCI, Wijesuriya day of physical or mental exertion, contrasted to a state of chronic excessive tiredness. Furthermore, there is general agreement that fatigue is a complex phenomenon involving physical, psychosocial, and behavioral processes including (1) feelings of mental and physical tiredness, (2) associated negative mood states such as anxiety, (3) reduced alertness that impairs willingness to perform a task, (4) decrements in cognitive and psychomotor performance, and (5) circadian rhythm and homeostatic influences. 22,24,26 As 1 of its multidimensional domains, the SF-36 assesses vitality, 16 which is a measure of a person s capacity to cope with life pressures and challenges with energy, vigor, and a joie de vivre. 16 However, fatigue, as defined above, encompasses more than just energy levels, though it is a reasonable assumption that fatigue would be elevated when vitality levels are low. Chronic fatigue is associated with many disorders, such as major depressive disorder, multiple sclerosis, and traumatic brain injury (TBI), and fatigue most likely occurs as a consequence of living with the injury. 22,24 TBI has been found to be associated with elevated fatigue and decreased vitality. 23 In a study of 452 adult participants with minor to severe TBI, almost 70% of participants reported problems with significant fatigue. 23 Fatigue is also a recognized problem for people with SCI. People with SCI have been shown to have over 7 times the risk of increased levels of negative mood states compared with able-bodied controls, and fatigue was 1 of the negative mood states assessed. 27 Krause et al 28 found fatigue was consistently associated with dysphoric mood in persons with SCI. Richardson and Richards 29 investigated depressive symptoms in a large group of people with SCI over 4 time periods up to 25-years postinjury. They found sleep disturbance and fatigue to be consistent negative factors associated with reduced life satisfaction. Thompson 30 found that fatigue was the most frequent problem in 150 adults with SCI attending an outpatient SCI clinic, followed by pain and physical weakness. Fawkes- Kirby et al 31 found that almost 60% of a SCI outpatient sample had levels of fatigue severe enough to interfere with function. Results of qualitative research in persons with SCI suggested that fatigue was a major negative factor associated with SCI, 32 and fatigue was found to be more commonly reported by younger persons with SCI. 10 Finally, Middleton et al 3 found that vitality in people with SCI was significantly and substantially reduced compared with Australian norms. Notwithstanding the above research, investigation into the nature of fatigue and its impact on well-being after SCI has been limited. Therefore, the main objective of the research presented in this article was to investigate the influence of fatigue on the HR-QOL of people with SCI. It was hypothesized that for the same level of fatigue, people with SCI will have lower HR-QOL. METHODS Participants Participants included 41 persons with SCI who were living in the community and 41 able-bodied controls. The participants with SCI were enrolled into the study from SCI rehabilitation unit contacts as well as through advertising in relevant newsletters and magazines. The controls were enrolled into the study through community advertising, and were only admitted into the study if they stated they were free of chronic physical or mental disease at the time of assessment. The 41 controls were selected and matched to the participants with SCI for sex and age ( 5y) on a case by case basis from a sample of over 100 able-bodied participants who, along with the participants with SCI, had enrolled in a larger study concerning the neuropsychophysiology of fatigue. The mean age SD for the SCI group was years (range, 21 70y), and the group was comprised of 39 men and 2 women. The mean age SD for the controls was years (range, 21 70y), and the sample was also comprised of 39 men and 2 women. The 2 women in each group were aged in the mid 50s to early 60s, and they had similar scores on the HR-QOL and fatigue measures similar to the majority of men. Most of the persons with SCI had paraplegia (n 27), while 44% were assessed by a medical specialist as having complete lesions. The mean time since the injury SD was years (range, 1 48y since injury). In terms of cause of injury, the majority (n 23) sustained a SCI due to a motor vehicle accident, followed by falls (n 9), sporting related injuries (n 6), and medical conditions (n 3). The number of years of education was collected for both groups. The controls had a slightly higher number of years of education than the SCI group (controls mean years SD, 16 2; SCI mean years SD, 14 3). The presence of a TBI was established by requesting information about their initial injury in the prestudy interview. The majority of the SCI sample did not have a comorbid TBI (n 32). The majority of the participants with SCI (n 24) were on medications that included analgesics, antispasmodics, hypnotics, and antidepressants. Measures Measures reported in this study include the SF-36 16,33 to measure HR-QOL, and the Iowa Fatigue Scale 34 to measure fatigue levels. Scores on the SF-36 have been shown to have acceptable reliability and validity in various populations, including Australian. 16,35,36 The SF-36 questionnaire was scored by summing and transforming raw data for each of the 8 domains as per the formula in the SF-36 manual. 33 Higher scores on the 8 domains suggest higher HR-QOL. The 8 SF-36 domains include: (1) physical functioning, indicating the extent to which a person s health limits their day to day physical activities; (2) role limitations at work or in the home due to physical health problems (role-physical); (3) bodily pain, indicating the extent to which pain interferes with daily activities; (4) general health status and perception of health; (5) vitality, a measure of a person s energy levels; (6) social function, indicating the extent to which health limits social activities; (7) role limitations due to emotional problems (role-emotional), indicating the extent to which a person s emotional problems impact on daily and work activities; and (8) mental health, indicating the amount of time a person experiences feelings of nervousness, depression, happiness, and so on. The Iowa Fatigue Scale is an 11-item measure of fatigue over the past 4 weeks. The Iowa Fatigue Scale provides an assessment of fatigue in terms of cognitive function, drowsiness, energy level, and productivity, with a higher score indicating greater fatigue. 34 Scores on the Iowa Fatigue Scale have acceptable internal consistency (Cronbach.90) and are correlated with other measures of fatigue (r.90). An Iowa Fatigue Scale total score close to or over 30 indicates a substantial fatigue problem. 34 The Iowa Fatigue Scale has 4 factors, including cognitive functioning (I have trouble concentrating), aspects of fatigue (I feel worn out), aspects of energy (I feel energetic), and the fourth factor includes aspects of productivity (I have low output). 34 Scores on these 4 factors have been shown to have acceptable internal reliability (ie, Cronbach.84) and acceptable discriminant validity. In addition to HR-QOL and fatigue, an assessment of the SCI group s participation in their family and community, social mobility, and social roles was conducted. The Community Integration Ques-

3 FATIGUE ASSOCIATED WITH SCI, Wijesuriya 321 Table 1: SF-36 Domain Scores for the SCI and Able-Bodied Groups, As Well As SF-36 Domain Scores (except Vitality) for the 4 Subgroups, That is, Low Versus High Levels of Fatigue for the SCI and Control Groups SF-36 Domain Aust. SF-36 Norms. SCI Group (n 41) Controls (n 41) Low Fatigue High Fatigue SCI (n 18) Controls (n 29) SCI (n 23) Controls (n 12) Physical functioning (27 43) (84 95) (31 58) (83 97) (18 37) (78 95) Role-physical (43 69) (89 100) (69 97) (93 101) (18 52) (72 103) Bodily pain (47 65) (76 86) (62 83) (76 88) (33 55) (67 88) General health (46 62) (67 78) (62 76) (70 82) (32 53) (52 79) Vitality 64.5* (49 62) (63 72) Social function (58 78) (82 94) (70 89) (79 83) (44 74) (81 105) Role-emotional (73 93) (81 98) (86 103) (78 99) (58 90) (73 110) Mental health (69 80) (74 83) (75 87) (78 87) (61 78) (59 76) NOTE. Values are mean SD (95% confidence intervals) or as otherwise indicated. Low fatigue is a score of 25 on the Iowa Fatigue Scale; high fatigue is score of 25 on the Iowa Fatigue Scale. Abbreviation: Aust. SF-36 Norms., Australian SF-36 age standardized norms are provided along with 1 sample t test significance levels of the difference to the SCI SF-36 mean scores. *P.01; P.001. tionnaire (CIQ) was used to assess this construct. 37 The CIQ was primarily developed to assess community participation in people with TBI; however, the CIQ items were written so that people without injury could also complete the scale, 37 as demonstrated in the following typical items Who usually prepares meals in your household? and Approximately how many times a month do you usually participate in shopping outside your home? Higher scores on the CIQ suggest better social integration. Discriminant validity and internal reliability of the scores on the CIQ have been shown to be acceptable (coefficient of 0.80). 37 Analysis For the factorial analysis of variance (ANOVA), the SCI and able-bodied control groups were divided into fatigue subgroups by dichotomizing on the basis of the SCI group Iowa Fatigue Scale median score of 25. Scores less than 25 constituted the low fatigue subgroups and scores equal or above 25 became the high fatigue subgroups in both the SCI and control groups. A split method was used as it resulted in the groups having highly contrasting scores (ie, the low group had a very low fatigue mean score SD of , while the high group had a severe fatigue mean score SD of ). The split method was also used as it maintained adequate numbers in each subgroup. Mean values for the 8 SF-36 domains and Iowa Fatigue Scale scores were calculated for the 4 subgroups, and the significance of differences was determined by factorial ANOVA. The SF-36 vitality domain was removed from the analysis given that it is a construct similar to fatigue; therefore, only 7 SF-36 domains were entered into the analysis. Assuming a medium effect size (Cohen d) based on prior work on differences in fatigue and HR-QOL between people with SCI and controls, 3,27 a priori statistical power was estimated to be around 60% to 70%. Eta-squared ( 2 ) values are provided as an estimate of the size of the difference between the 2 samples. An eta-squared of around.03 is considered small,.13 is considered a medium difference, and over.20 is considered a large and substantial difference. 38 Post hoc statistical power is also provided with the analyses. All analyses were performed using Statistica Software. a RESULTS Table 1 shows descriptive statistic values for all 8 SF-36 domain scores for the SCI and control groups. Significant differences (df 1,78) between the 2 groups were found for the physical functioning (F 111, P.001, 2.61), role-physical (F 27, P.001, 2.27), bodily pain (F 21, P.001, 2.23), general health (F 11, P.001, 2.16), vitality (F 8, P.05, 2.10), and social function (F 13, P.001, 2.14) domains with moderate to large effect sizes. However, no significant differences were found for role-emotional and mental health. Australian age standardized SF-36 norms are also provided in table 1, along with the level of significance of the difference to the SCI group. 35 Table 2 shows the Iowa Fatigue Scale scores for the 2 groups as well as F values, significance levels, and effect sizes. The SCI sample was found to have significantly elevated fatigue for the total IFS score, as well as for the cognitive factor (eg, feel slowed down in their thinking), fatigue factor (eg, feeling worn out and drowsy), and productivity factor (eg, feeling that they have reduced output in a day). There was a nonsignificant trend for the SCI group to have low energy levels. A contingency analysis ( , P.05) and odds ratio analysis (odds ratio 3.1) based on the median IFS score of 25, revealed that people in the SCI group Table 2: Descriptive Statistics for the SCI Group and the Able-Bodied Controls for the Iowa Fatigue Scale and the 4 Iowa Fatigue Scale Factors Variable SCI Group (n 41) Controls (n 41) F Effect Size (ŋ 2 ) Total Iowa Fatigue Scale ( ) ( ) Cognitive ( ) ( ) 5.5*.06 Fatigue ( ) ( ) 4.4*.05 Energy ( ) ( ) Productivity ( ) ( ) NOTE. Values are mean SD (95% confidence intervals) or as otherwise indicated. *P.05; P.01.

4 322 FATIGUE ASSOCIATED WITH SCI, Wijesuriya had over 3 times the risk of having clinically elevated levels of fatigue in comparison with the able-bodied group. In comparative frequencies, 56.1% of the SCI group and 29.2% of the controls had high levels of fatigue. The SCI group had significantly lower community integration scores compared with nondisabled norms (mean SCI CIQ SD, 17 4; mean control CIQ SD, 21 3; t 5.3; P.01) reported by Willer et al. 37 Pearson correlation analyses were performed to calculate the relationship between fatigue and demographic and injury factors for the SCI sample. No significant associations were found between fatigue and age (r.05), level of injury (r.09), TBI (r.15), completeness of lesion (r.09), years of education (r.31), extent of community integration (r.02), and taking medications or not (r.15). Only time since injury was found to be associated with fatigue (r.44, P.01), where higher fatigue levels were more likely to be found with less time since injury. This finding was supported by the significant association found between the SF-36 vitality domain and time since injury (r.53, P.010), where higher levels of vitality were related to longer time since injury. Table 3 shows Pearson correlations between the fatigue measures and all the SF-36 domains for the SCI group. Table 1 also shows mean SF-36 scores for the low and high fatigue SCI and control subgroups. The results for the ANOVA (df 1,78) indicated a significant main effect for the level of fatigue for physical functioning (F 5, P.05, 2.06), rolephysical (F 21, P.001, 2.21), bodily pain (F 13, P.001, 2.14), general health (F 17, P.001, 2.18), and mental health (F 16, P.001, 2.17), while no significant differences were found for the social function and roleemotional domains. Participants in the high fatigue SCI and control subgroups tended to have lower HR-QOL. Significant level of fatigue group interactions were found for the rolephysical (F 9, P.01, 2.11), bodily pain (F 6, P.05, 2.08), and social function (F 6, P.05, 2.07) domains, and an example interaction effect (role-physical) is shown in figure 1, with the other 2 interaction effects being similar. Post hoc Bonferroni tests confirmed that both the low-fatigue groups and the high-fatigue control group had statistically comparable HR-QOL scores for these 3 SF-36 domains. However, the high fatigue SCI subgroup had significantly lower HR-QOL scores compared with the other 3 fatigue subgroups (P.001 for role-physical and bodily pain, and P.05 for social function). Retrospective statistical power analyses indicated power to range from 80% to 99% for the factorial ANOVAs. Table 3: Pearson Correlation Table for the Total Iowa Fatigue Scale Score and 4 Iowa Fatigue Scale Factors With the SF-36 Domains for the SCI Group Only SF-36 Total IFS IFS Scores Cognitive Fatigue Energy Productivity Physical *.28 functioning Role-physical Pain * Health Vitality Social.41.37* * Role-emotional Mental.35.39* NOTE. Statistically significant probabilities are shown. *P.05; P.01; P.001. Fig 1. Shows the influence of fatigue on SF-36 Role-physical domain. SCI and able-bodied persons with low fatigue are compared with those with higher fatigue. Confidence intervals (95%) are shown. DISCUSSION The research presented in this article confirms prior findings of a negative HR-QOL burden being associated with SCI. 1-3,7 However, the actual HR-QOL domains impacted still need some clarification. Most studies have found large reductions in HR-QOL domains such as physical functioning, role-physical, social function, bodily pain, general health, and vitality. 1-3,7 However, the impact of SCI on the role-emotional and mental health domains is arguable. Middleton et al 3 found significant and large reductions in all SF-36 domains including mental health and role-emotional, while others have not found significant reductions in mental health. 7 The findings presented in this article suggest that sustaining a SCI does not in itself result in significantly lower HR-QOL in the mental health and roleemotional domains. Nevertheless, there is a subgroup of persons with SCI, estimated to be around 40%, who are at risk of experiencing psychological disorder, such as depression and anxiety disorder, 9,20 and research is needed to isolate characteristics typical of those at risk. For instance, those identified to be at risk include people with SCI who believe they have no ability to influence their lives (described as poor self-efficacy), as well as those with severe chronic pain. 3 People with SCI were found to have significantly and clinically elevated levels of fatigue compared with able-bodied controls of a similar age (based on the assumption that a total Iowa Fatigue Scale score of close to 30 is clinically severe). 34 The prevalence of fatigue in the SCI group was high, as demonstrated by the results of the contingency analysis which found the SCI group had over 3 times the odds of being fatigued, compared with the control group. What factors make a person with SCI vulnerable to suffering elevated fatigue? Injury-related factors, such as level and completeness of lesion and taking potentially sedating medications for pain and spasticity management, were not found to be influential factors. Neither were demographic factors such as age, years of education, or community integration. However, time since injury was found to be negatively related to fatigue. Those persons with SCI who had their injury fewer than 9 years ago (9 being the median SCI group value for time since injury) had severely elevated fatigue levels (mean Iowa Fatigue Scale score 29) in comparison with those who had their SCI over 9 years ago

5 FATIGUE ASSOCIATED WITH SCI, Wijesuriya 323 (mean Iowa Fatigue Scale score 23). Further research will need to be conducted to investigate why this is the case. Research has found younger persons with SCI to be more susceptible to fatigue 10 ; however, we did not find age to be a significant factor. Perhaps the more potent factor is the amount of time elapsed since the injury? As time passes, the majority of persons with SCI will begin to adjust to their injury and related impairments, with better fitness, improved coping and participation, and as a result vulnerability to fatigue may become lower. Furthermore, the lowered fatigue associated with a longer time since injury could also be related to undiagnosed medical conditions (eg, obstructive sleep apnoea) that are detected and treated in the long-term postinjury. Research is required to clarify factors that may precipitate and exacerbate fatigue over time. Breaking down the Iowa Fatigue Scale into the 4 Iowa Fatigue Scale factors provided additional insight into the dynamics of fatigue associated with SCI. The participants with SCI had significantly elevated scores on the Iowa Fatigue Scale cognitive, fatigue, and productivity factors, while there was a nonsignificant trend for the SCI group to have reduced energy. Cognition-related aspects of fatigue, such as poor concentration and reduced memory, were increased in the SCI group in comparison with the controls. Cognition-related aspects of fatigue correlated strongly with all the SF-36 domains, except with physical functioning. On a cautionary note, the elevated cognitive fatigue symptoms do overlap with depressive mood symptoms 9,39,40 ; therefore, care should be taken during diagnostic assessment of a person with SCI to distinguish between primary cognition-related fatigue problems and mood disorder symptoms. The SCI group was also significantly more likely to have feelings of drowsiness and feeling worn out in comparison with the controls. These feelings were found to be significantly associated with bodily pain, general health, role-physical, and vitality domains, but not to the psychosocial SF-36 domains. Productivity was significantly lower in the SCI group than the able-bodied controls. Clearly, fatigue exacts a heavy toll, not only in a person with SCI feeling worn out and cognitively challenged, but also in limiting their daily achievements. The Iowa Fatigue Scale productivity factor was significantly correlated with all SF-36 domains except physical functioning and mental health. A nonsignificant trend was found for the SCI group to have reduced energy levels. The major finding of this research was the interaction effect of independent factors level of fatigue and the presence of SCI on HR-QOL. This effect is illustrated in figure 1 for the role-physical domain. Significant interactions occurred for the role-physical, bodily pain, and social function domains, and the interactions were close to significance for the general health and roleemotional domains (P.06 and.07, respectively). Essentially, the interaction effect is the same for all 3 domains, and indicates that if a person with SCI has high levels of fatigue, the negative impact on their HR-QOL is substantial. In contrast, able-bodied controls with high levels of fatigue did not have significantly reduced HR-QOL, nor did this occur for those persons with SCI who had low fatigue levels. Furthermore, there was no difference in HR-QOL scores between participants with SCI and low fatigue levels and the able-bodied controls with low fatigue levels. These findings highlight the fact that a catastrophic injury like SCI does not invariably result in substantial reductions in HR-QOL in the long term. Based on the data presented in this article, we argue that if fatigue levels are low, the well-being of people with SCI can be similar to healthy, able-bodied people. A similar conclusion was reached by Middleton et al 3 when they showed that high self-efficacy acts in a protective manner, boosting HR-QOL in people with SCI to similar levels to that of those in the Australian able-bodied population. The factorial ANOVA results did not indicate significant interaction effects for the physical functioning and mental health domains. However, a main effect was found in which physical functioning was significantly and substantially reduced in the SCI group compared with the controls, regardless of fatigue levels, though a trend existed for physical functioning to be reduced further in the high fatigue SCI group. This result supports the findings of others who have shown SCI results in very substantial physical function deficits. 1-3,5 The mental health results were intriguing. Participants in the high fatigue subgroup in both the SCI and able-bodied groups had comparable and very significant reductions in the SF-36 mental health domain. This finding demonstrates that fatigue has a potential toxic and harmful effect on mental health, regardless of whether a person has a severe and chronic neurologic condition. Study Limitations Limitations exist that require discussion. First, the number of participants in the 2 groups was not large, and dichotomizing the groups to investigate the influence of fatigue on HR-QOL resulted in lowered statistical power. However, a priori power analysis estimated power to be in the region of 60% to 70%, while retrospective power analyses indicated that the statistical power in the study was sufficient (ie, 80% 99%), thus reducing risks of type II error rates. 38 Second, the use of self-report measures to assess all variables is a limitation. Future research in this area should be designed to include physical or behavioral measures, for instance, a physiologic measure of fatigue such as electrooculography. 26 Third, the study findings would be supported by replication, as well as by the provision of longitudinal data in which persons with SCI are assessed over a period of time that spans the rehabilitation phase as well as time living in the community. Fourth, the response to some items in the Iowa Fatigue Scale may result in an inflation of the level of fatigue due to the presence of a SCI (eg, Physically, I feel in good shape. ), or due to a comorbid condition such as TBI or depression (eg, I have trouble with my memory. ). However, the presence of TBI was not found to be significantly correlated with Iowa Fatigue Scale fatigue scores in the SCI sample. Future research will need to examine the validity of using the Iowa Fatigue Scale with SCI populations. CONCLUSIONS Due to necessity, most resources in SCI rehabilitation are employed to address the obvious physical impairment, activity limitations, discharge planning issues, and common secondary conditions associated with SCI such as pain and risk of urinary infection. 1,3,5 Clearly, the challenges associated with SCI are huge and require a substantial continued input of resources so as to best assist the person with SCI to make the necessary personal and social adjustments. 13,41 The results of this study have indicated that over 50% of a sample of adults with SCI, with a mean time since injury of around 16 years duration, had severe levels of fatigue and substantial associated reductions in HR-QOL. Given this finding, it would be beneficial if future research were to focus on fatigue in people with SCI, beginning in the rehabilitation phase and continuing assessment as they settle into their communities. This should involve the search for factors that exacerbate fatigue, such as chronic pain, older age, or the presence of depressive mood. The possible benefits of such research would be improved risk assessment, and the provision of invaluable data on the impact of fatigue on the adjustment and resilience of people with SCI. 39,41

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