The situational fatigue scale: A different approach to measuring fatigue

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(1)Quality of Life Research (2005) 14: 1357–1362 DOI 10.1007/s11136-004-5680-0. Ó Springer 2005. The Situational Fatigue Scale: A different approach to measuring fatigue Chien-Ming Yang1 & Chih-Hsing Wu2 1 Department of Psychology, National Chengchi University, Taipei, Taiwan (E-mail: yangcm@nccu.edu.tw); 2 Department of Family Medicine, National Cheng-Kung University, Tainan, Taiwan Accepted in revised form 31 October 2004. Abstract Fatigue can be defined as a subjective state of an imbalance in the availability of inner resources needed to perform physical or mental activities. The level of fatigue is determined not only by the availability of inner resources but also by the demands of the activities performed. Most conventional fatigue scales require subjects to rate their level of fatigue without specifying the situation. In the present study, we constructed a subjective rating scale, the Situational Fatigue Scale (SFS), with which subjects estimated their level of fatigue in specific activities of daily life. We administered the SFS, along with the Fatigue Assessment Instrument (FAI) to 96 outpatients in a family-medicine clinic and to 62 college students to assess the psychometric properties of the SFS. Principle component analysis revealed two underlying factors: physical fatigue and mental fatigue. SFS scores were significantly correlated with several FAI scores and differentiated patients complaining of fatigue from those who did not. The SFS also showed good internal consistency and test–retest reliability. These results suggest that the SFS could be a useful tool to measure a different dimension of the broad concept of fatigue. Key words: Fatigue, Rating scale, Reliability, Validity Abbreviations: DEFS – Dutch Exertion Fatigue Scale; FAI – Fatigue Assessment Instrument; MFS – Mental Fatigue Subscale; PFS – Physical Fatigue Subscale; SFS – Situational Fatigue Scale. Introduction Fatigue is one of the most common health complaints and affects different aspects of an individual’s quality of life. Fatigue has been reported in approximately 10–45% of community samples and in patients examined in primary-care settings; the rates vary depending on the methods used and the populations surveyed [1–3]. Fatigue is a complex and multidimensional phenomenon that can be defined from different perspectives [4, 5]. The North American Nursing Diagnosis Association (NANDA) defined fatigue as ‘an overwhelming, sustained sense of exhaustion and decreased capacity for physical and mental work’ [6]. Aaronson, after reviewing dif-. ferent definitions, defined fatigue as ‘the awareness of a decreased capacity for physical and/or mental activity due to an imbalance in the availability, utilization, and/or restoration of resources needed to perform activity’ [4]. The definitions suggest that fatigue is determined by one’s subjective feeling about the state of his or her internal resources and also by the demands of the activity (or the ‘physical and mental work’) being performed. In clinical populations, various pathologies can reduce a patient’s internal resources and thus lead to fatigue. In healthy individuals, increased demands or activities can induce fatigue. Therefore, to measure fatigue, one should consider both the individuals’ internal resources and the situational context..

(2) 1358 Several approaches have been developed to measure fatigue. Some assess the severity of symptomatic complaints, distress, or functional impact of fatigue. Examples include the item ‘Fatigue interferes with my physical functioning’. On the Fatigue Severity Scale [7] and ‘To what degree is the fatigue you are feeling now interfering with your ability to visit or socialize with your friends?’ on the Revised Piper Fatigue Scale [8]. These items emphasize the ‘interferences’ caused by fatigue and specify the associated symptoms or affected functions to be rated. Most of these scales were designed as tools for screening/diagnosing, treating, or evaluating patients with fatigue-related medical conditions. They provide clinically valuable information and have had good reliability and validity in clinical populations [7–10]. However, these scales may not be sensitive to fatigue that does not cause significant functional impairments. Fatigue is not necessarily a symptom of disease but may be a daily experience of persons in the general population. Several researchers have differentiated the ‘acute fatigue’ and ‘normative fatigue’ caused by daily life or extensive activities from the ‘chronic fatigue’ associated with prolonged stress or pathologies [11, 12]. The scales measuring functional impacts of fatigue may be limited in the evaluation of this ‘normal range’ of fatigue. Some other approaches assess the subjective quantification of fatigue or related concepts directly. Examples include items asking subjects to rate their general level of fatigue or fatigability directly on a Likert or a visual analog scale [13, 14], and instruments that require subjects to rate their subjective feelings about adjectives used to characterize fatigue or brief descriptions of different dimensions of fatigue, such as ‘active’, ‘tired’, ‘worn out’, or having a ‘desire to lie down’ [15–17]. These scales have generated valid results in studies with both clinical and non-clinical populations [13–17]. Since these scales require subjects to rate their level of fatigue without specifying the situational context, the obtained ratings reflect the feeling of availability of the inner resources to fulfill demands of the individuals’ daily life activities. Therefore, the level of fatigue in a patient with chronic illness may be rated the same as that in a healthy individual working three jobs, though the fatigue is from different sources. When the purpose of the measure is to assess the level of. fatigue in response to the same daily life activity level, these scales may not be valid instruments. The rating may be confounded by individual differences in daily routines. To avoid this confounding, one should measure the level of fatigue under a given set of daily life conditions. To our knowledge, only one scale, the Dutch Exertion Fatigue Scale (DEFS), has attempted to measure fatigue by specifically describing fatigueinducing situations [18]. The authors of this scale called the fatigue associated with performing certain activities ‘exertion fatigue’. The DEFS contains nine-item Likert-scales to assess the level of fatigue, each corresponding to a given activity of daily life (such as walking for 30 min, shopping, or visiting someone). Some items may still be too general for a critical evaluation of fatigue levels. Only two items refer to a specific length of time for a particular activity. However, the duration is important because, for example, shopping for 30 min could result in substantially less fatigue than shopping for 3 hours. Without specifying the length of time, raters are more likely to provide an estimate based on their general feelings of their overall inner status. Also, previous research has shown that fatigue has physical and mental dimensions [19]. The DEFS contains no items concerning fatigue associated with activities involving primarily mental effort. Although the mental aspect of fatigue is included in the DUFS (Dutch Fatigue Scale), which was constructed by the authors of the DEFS, the activities involving mental efforts were not well described either [18]. Therefore, there is a need to develop another scale that measures both mental and physical fatigue while taking situational demands into consideration. The primary goal of this study was to develop such as scale – the Situational Fatigue Scale (SFS) – and then to evaluate its validity and reliability. In designing the SFS, we interviewed healthy individuals to identify activities involving different levels of physical and mental effort and to determine the length of activity engagement needed to generate fatigue. We then conducted two studies: one to evaluate the construct, internal consistency, and validity of the SFS in a clinical population and the second to evaluate the internal consistency and test–retest reliability of the SFS in a healthy population..

(3) 1359 Methods Construction of the SFS Thirty individuals (15 male and 15 female), with no reported current medical conditions, were interviewed to collect data about activities of daily life that may lead to fatigue. Their age ranged from 21 to 57 years (21–30 years old: n ¼ 11; 31–40 years old: n ¼ 9; 41–50 years old: n ¼ 6; 51–57 years old: n ¼ 4). All were blinded to the purpose of the study. The participants were asked to list all of their activities of daily life that might cause fatigue. A list of 32 different activities was obtained after similar activities were combined. Only the 13 activities that were reported by at least two participants were selected to be items on the SFS (see the Appendix A). Forty-three healthy individuals (22 male and 21 female) aged 18–59 years were then recruited from a college campus and offices and given the list of 13 activities. They were asked to estimate how long they would have to be engaged in each activity to experience fatigue. The median length of time reported for each activity was used to specify the duration of the items included on the SFS (see the Appendix A). A six-point Likert scale was used for each item, with scores ranging from 0 ¼ ‘not fatigued at all’ to 5 ¼ ‘extremely fatigued’. The summation of their ratings for each item was used to determine the total score and subscale scores of the SFS. The original SFS was constructed in Chinese language. The English version in the Appendix A was translated with the consultation with a professional translator who is a native English speaker.. package that included the SFS; the Fatigue Assessment Instrument (FAI) [13]; and a simple questionnaire, which was used to record the patient’s demographic information and chief complaint(s) and to ask a single question: ‘Is fatigue one of your problems?’ The FAI was a 29-item rating scale consisting of four underlying constructs: the severity of fatigue, the sensitivity of one’s fatigue in a particular circumstance (such as heat, cold, or stress), the consequences of fatigue, and the response of fatigue to rest and/or sleep. Internal consistency of the SFS was assessed with Cronbach’s a test. Principle component analysis was also conducted to investigate the underlying factors of the SFS. The validity of the scale was evaluated by correlating SFS scores with FAI results and by comparing SFS scores between patients reporting fatigue and those denying fatigue with an independent-group t-test. Study 2 To investigate the internal consistency and the test–retest reliability of the scale, the SFS was administered repeatedly to 63 college students (23 male and 40 female) with a mean age of 21.0 years (SD ¼ 1.99). They were recruited from two introductory psychology courses. The SFS was administered twice to each participant with an inter-test interval of 3–4 weeks. Test–retest reliability was assessed by performing Pearson correlations between the scores obtained on the two occasions. Cronbach’s a test was also conducted to evaluate the internal consistency of the scale.. Study 1. Results. Ninety-six patients (45 male and 51 female) aged 18–60 years (mean ¼ 31.1 years, SD ¼ 10.0) were recruited from an outpatient clinic of a family medicine department in a general hospital. They were randomly selected at different times of day immediately after they completed registration and as they were waiting to be seen by the physicians. These patients attended the clinic for a variety of conditions, which ranged from acute maladies, such as the flu and stomachaches, to chronic illness such as diabetes and hypertension. Trained graduate students individually administered a survey. Study 1 Principle component analysis with varimax rotation was conducted to assess the underlying factors of the SFS. A loading value of 0.5 was used as the cut-off to determine the factors. The results revealed two underlying factors. The first (generated with items 5– 13) consisted of activities that required more mental effort than physical effort, and the second (generated with items 1–4) was characterized by predominantly physical activities (see Table 1). Therefore, we divided the SFS into a Physical Fatigue Subscale (PFS).

(4) 1360 based on items 1–4 and a Mental Fatigue Subscale (MFS) based on items 5–13. Cronbach’s a coefficients indicated good internal consistency for the overall scale (Cronbach’s a ¼ 0.90), as well as for the PFS (Cronbach’s a ¼ 0.88) and the MFS (Cronbach’s a ¼ 0.89). The subjects were divided into two groups according to their answers to the single question of whether fatigue was one of their problems. Of the 96 participants, 51 (20 males and 31 females, mean age ¼ 31.8 ± 9.9) reported experiencing problems of fatigue, and 45 (25 males and 20 females, mean age ¼ 30.3 ± 10.1) did not. To evaluate the relative discriminability of the scales, we conducted an independent-group t-test to determine the extent to which the overall SFS scores differed between the two groups. The mean total SFS scores were 26.6 (SD ¼ 10.9) for the group reporting fatigue and 18.0 (SD ¼ 10.9) for the group that did not. The difference was statistically significant (t ¼ 3.9, p < 0.001). When we examined the subscales separately, the group reporting fatigue had a mean PFS score of 9.5 (SD ¼ 4.6) and a mean MFS score of 17.2 (SD ¼ 8.2); the other group had a mean PFS score of 5.5 (SD ¼ 3.8) and a mean MFS score of 12.5 (SD ¼ 8.5). Results for both the PFS and the MFS were significantly different between the two groups (t ¼ 4.5, p < 0.001 and t ¼ 2.7, Table 1. Factor loading values with principal components analysis Item. 1. Playing a ball gamea 2. Jogginga 3. Taking a walka 4. Cleaning housea 5. Readingb 6. Watching TVb 7. Chattingb 8. Shoppingb 9. Drivingb 10. Hosting a social eventb 11. Doing paperworkb 12. Meetingb 13. Attending a social activityb a b. Factor 1. Factor 2. Mental Fatigue. Physical Fatigue. 0.018 0.153 0.172 0.383 0.615 0.736 0.648 0.593 0.617 0.759 0.763 0.705 0.774. 0.862 0.877 0.863 0.716 0.265 )0.013 0.313 0.400 0.466 0.357 )0.047 0.167 0.138. Items of the Physical Fatigue Subscale (item 1–4). Items of the Mental Fatigue Subscale (item 5–13).. p < 0.01, respectively). Table 2 lists the mean SFS scores, standard deviations, and results of t-tests. Pearson correlations were conducted to assess criteria-related validity between SFS and FAI scores. Total scores on the SFS and the FAI were moderately correlated (r ¼ 0.47, p < 0.001). Scores derived from the SFS demonstrated modest correlation with the ‘fatigue severity’ and ‘consequences of fatigue’ subscales of the FAI (r ¼ 0.30–0.38). Total SFS scores (r ¼ 0.26, p < 0.05) and MFS scores (r ¼ 0.28, p < 0.01) were weakly correlated with results of the ‘fatigue under particular circumstances’ subscale of the FAI. Similarly, the PFS (r ¼ )0.23, p < 0.05) was weakly correlated with the ‘response to rest/sleep’ subscale of the FAI. Table 3 lists all of the correlation coefficients. Study 2 The test–retest correlation yielded a coefficient of 0.69 for the total scale, 0.65 for the PFS, and 0.69 for the MFS (all p < 0.001). These results indicated good test–retest reliability of the scales when individual fluctuations in fatigue were considered. Cronbach’s a coefficients indicated reasonable internal consistency for the overall scale (Cronbach’s a ¼ 0.76), as well as for the PFS (Cronbach’s a ¼ 0.64) and the MFS (Cronbach’s a ¼ 0.75).. Discussion Although many scales have been developed to measure fatigue, the SFS is unique in that it asks subjects to estimate their level of mental and physical fatigue in the context of specific daily activities. It is designed in this way to measure the Table 2. Comparisons of the SFS scores between patients with and without fatigue complaints. Total SFS score PFS Subscale MFS Subscale. Fatigue N. Mean. SD. t. Yes No Yes No Yes No. 26.6 18.0 9.5 5.5 17.2 12.5. 10.9 10.9 4.6 3.8 8.2 8.5. 3.9 <0.001. 51 45 51 45 51 45. P. 4.5 <0.001 2.7 0.008. SFS: Situational Fatigue Scale; PFS: Physical Fatigue Subscale; MFS: Mental Fatigue Subscale..

(5) 1361 Table 3. Correlation coefficients between the SFS scores and the FAI scores The SFS Total score. The FAI Total score Fatigue severity Circumstances Consequences Rest/Sleep. PFS subscale. MFS subscale. r. p. r. p. r. p. 0.47 0.38 0.26 0.37 )0.14. <0.001 <0.001 0.011 <0.001 0.173. 0.40 0.38 0.13 0.33 )0.23. <0.001 <0.001 221 0.001 0.022. 0.41 0.30 0.28 0.32 )0.06. <0.001 0.003 0.006 0.001 0.545. SFS: Situational Fatigue Scale; PFS: Physical Fatigue Subscale; MFS: Mental Fatigue Subscale; FAI: Fatigue Assessment Instrument.. availability of inner resources while controlling the demands of situational context. It targets a specific dimension of the broad concept of fatigue that is different from what is measured by other conventional fatigue rating scales. This scale can be used alone or in combination with other scales to expose the multiple faces of fatigue across all populations. The principle component analysis revealed two underlying constructs of the SFS: physical fatigue and mental fatigue. These results were consistent with findings of previous studies [5, 19]. In terms of reliability, the SFS had good internal consistency for the total scale and also for the MFS and the PFS, in both clinical populations and healthy young adults. In addition, test–retest reliability was reasonably consistent over the 3–4-week testing period, in light of the presumed fluctuating nature of fatigue (r ¼ 0.65–0.67). In terms of validity, SFS scores were moderately correlated (r ¼ 0.47) with overall FAI ratings. The FAI tends to target the pathological aspects of fatigue, while the SFS attempts to measure fatigue in response to daily activities. It is reasonable to conclude that the moderate correlation between the two scales suggests good validity of the SFS. The SFS was best correlated with the ‘fatigue severity’ and ‘consequences of fatigue’ components of the FAI. Also, SFS scores were significantly different between patients complaining of fatigue and those who did not. These results further support the notion that the SFS is a valid instrument for assessing self-reported levels of fatigue among primary-care populations. The SFS may have a few limitations. One of our intentions in designing the SFS was to enable an assessment of fatigue that can eliminate con-. founding of differences between individuals’ daily life routines by specifying a set of situations in the scale. However, some individuals may have no recent experience with the specific activities listed on the scale; therefore, they may have difficulty in accurately judging their level of fatigue. In our experience, subjects usually provide an estimate by recalling similar experiences. Also, in the instruction of the SFS, respondents are asked to rate the level of fatigue they ‘might’ experience following the given activities. Therefore, it should be kept in mind that the ratings on the SFS reflect more an estimate of the fatigue level rather than the actual fatigue level responding to the daily life activities specified. Also, the reference time interval used in the SFS was ‘the past month’. We selected this time interval because fatigue could fluctuate in an individual. We assumed that a sample set of fatigue over a 1-month period reflected the general state of the individual. This assumption could be further tested in future studies. Furthermore, the validity of the SFS for the general population has not been fully evaluated. Also, the sample size of the present study is limited. Hence, future studies are needed to evaluate the SFS in different populations with larger sample size and to establish a cut-off score for clinically significant fatigue. In addition, the use of adjective checklists to measure fatigue has been shown to be influenced by social desirability and individual personality styles [20]. It is not clear whether this bias could be reduced when the situational context is specified, as is the case in the SFS. The influences of possible confounding factors, such as mood, level of fitness, personality style, and personal concerns, should be addressed in future studies..

(6) 1362 In summary, the SFS introduces a new way to measure a dimension of fatigue that is different from what is measured by the conventional fatigue rating scales. The scale is brief and simple to use. With further research, it could be a reliable and valid scale for the assessment of fatigue in both clinical and research settings. Acknowledgements This research was supported by National Science Council,Taiwan (Grant number NSC89-2413-H006-009). Appendix A. Situational Fatigue Scale Name: ID #: Gender: Age: Date: According to your general feelings for the past month, please rate the level of fatigue you might experience after engaging in the following activities. 0 = no fatigue at all; 5 = extreme fatigue. Activity Level of Fatigue 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.. 12. 13.. Playing a ball game for 30 min. Jogging for 20 min. Taking a walk for 1 hour. Cleaning house for 30 min. Reading (magazines or newspapers) for 1 hour. Watching TV for 2 hours. Chatting for 1 hour. Shopping for 1 hour. Driving for 1 hour. Hosting a social event for 30 min. Doing paperwork (e.g. typing, writing, accounting, or making plans) for 1 hour. Meeting for 2 hours. Attending a social activity for 1 hour.. 012345 012345 012345 012345 012345 012345 012345 012345 012345 012345 012345. 012345 012345. References 1. Lewis G, Wessely S. The epidemiology of fatigue: More questions than answers. J Epidemiol Commun H 1992; 46: 92–97. 2. Cathebras P, Robbins J, Kirmayer L, Hayton B. Fatigue in primary care: Prevalence, psychiatric comorbidity, illness behaviour and outcome. J Gen Intern Med 1992; 7: 276–286. 3. David A, Pelosi A, McDonald E, et al. Tired, weak or in need of rest: Fatigue among general practice attenders. Brit Med J 1990; 301: 1199–1202 4. Aaronson LS, Teel CS, Cassmeyer V, et al. Defining and measuring fatigue. Image: J Nurs Scholarship 1999; 31: 45–50.. 5. Tiesinga LJ, Dassen TWN, Halfens RJ. Fatigue: A summary of the definitions, dimensions, and indicators. Nursing Diagnosis 1996; 7: 51–62. 6. North American Nursing Diagnosis Association. Nursing Diagnoses: Definitions & Classification, 2003–2004. Philadelphia, PA: NANDA, 2004. 7. Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD. The fatigue severity scale: Application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol 1989; 46: 1121–1123. 8. Piper BF, Dibble SL, Dodd MJ, Weiss MC, Slaughter RE, Paul SM. The revised Piper Fatigue Scale: Psychometric evaluation in women with breath cancer. Oncol Nurs Forum 1998; 25: 677–684. 9. Schwartz AL. The Schwartz cancer fatigue scale: Testing reliability and validity. Oncol Nurs Forum 1998; 25: 711–717. 10. Zachrisson O, Regland B, Jahreskog M, Kron M, Gottfries CG. A rating scale for fibromyalgia and chronic fatigue syndrome (the Fibro Fatigue scale). J Psychosom Res 2002; 52: 501–509. 11. Piper B. Fatigue. In: Carrieri-Kohlman V, Lindsey A, West C (eds), Pathophysiological Phenomena in Nursing: Human Responses to Illness, 2nd ed. Philadelphia, PA: Saunders, 1993; 279–302. 12. Jensen S, Given BA. Fatigue affecting family caregivers of cancer patients. Cancer Nurs 1991; 14: 181–187. 13. Schwartz JE, Jandorf L, Krupp LB. The measurement of fatigue: A new instrument. J Psychosom Res 1993; 37: 753–762. 14. Smets EMA, Grassen B, Bonke B, De Haes JC. The Multidimensional Fatigue Inventory (MFI) psychometric qualities of an instrument to assess fatigue. J Psychosom Res 1995; 39: 315–325. 15. Lee KA, Hicks G, Nino-Murcia G. Validity and reliability of a scale to assess fatigue. Psychiatr Res 1991; 36: 291–298. 16. McNair DM, Lorr M, Droppleman LF. EDITS Manual for the Profile of Mood States. San Diego, CA: Educational and Industrial Testing Service, 1981. 17. Shapiro CM, Flanigan M, Fleming JAE, et al. Development of an adjective checklist to measure five FACES of fatigue and sleepiness: Data from a national survey of insomniacs. J Psychosom Res 2002; 52: 467–473. 18. Tiesinga LJ, Dassen TWN, Halfens RJG. DUFS and DEFS: Development, reliability and validity of Dutch Fatigue Scale and the Dutch Exertion Fatigue Scale. Int J Nurs Study 1998; 34: 115–123. 19. Chalder T, Berelowitz G, Pawlikowska T, Watts L, Wessely S, Wallace EP. Development of a fatigue scale. J Psychosom Res 1993; 37: 147–53. 20. May J, Kline P. Problems in using an adjective checklist to measure fatigue. Pers Indiv Differ 1988; 9: 831–832.. Address for correspondence: Chien-Ming Yang, National Chengchi University, Department of Psychology, 64, sec.2, Chih-Nan Rd., Taipei, Taiwan 116 Phone: +886-2-29387383; Fax: +886-2-29390644 E-mail: yangcm@nccu.edu.tw.

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