Fatigue following acquired brain injury (FABI): Advancing methods for treatment and assessment of fatigue for people living with an acquired brain injury

Fatigue is a common complaint among adults living with an acquired brain injury (ABI). Perceived fatigue can be persistent, disabling, and limiting for reintegration into everyday life. Despite the large impact of fatigue, scientific evidence is limited in guiding clinical practice for treating and assessing fatigue. This thesis comprises two research projects concerning rehabilitation of fatigue following ABI. The first project concerns the development of a treatment model for promoting self-management of fatigue. The second concerns the validation of the Danish translation of Dutch Multifactor Fatigue Scale (DMFS). In Denmark, a common approach to treating fatigue in neurorehabilitation includes educational and behavioral strategies, termed energy management (EM; energiforvaltning). However, the approach is not well defined. Consensus is lacking regarding its components, and underpinning treatment theories are largely unarticulated. Paper I, “Defining a Treatment Model for Self-Management of Fatigue Following Acquired Brain Injury: A Collective Case Study Using the Rehabilitation Treatment Specification System”, presents a model of EM based on practice-based routines and understandings at a specialized brain injury rehabilitation center. First, an initial model was co-produced with clinicians in iterative workshops using the Rehabilitation Treatment Specification System. Next, the model was refined in a collective case study of four individuals in vocational rehabilitation. The EM model comprises five main treatment components: (a) Knowledge and Understanding of Fatigue, (b) Interoceptive Attention of Fatigue, (c) Acceptance of Fatigue, (d) Activity Management, and (e) Self-Management of Fatigue. The model may facilitate theory-driven evaluation research and guide clinical decision-making in tailored treatment.
Treatment planning implies valid assessment instruments. DMFS addresses the multifaceted nature of fatigue following ABI in order to facilitate targeting of treatment to individual needs. DMFS comprises 38 items distributed on five subscales: (a) Impact of xii Fatigue, (b) Signs and Direct Consequences of Fatigue, (c) Mental Fatigue, (d) Physical Fatigue, and (e) Coping with Fatigue. A multicenter validation study on DMFS was conducted using both qualitative (Paper II) and quantitative (Paper III) methods. In Paper II, “Evaluation of Response Processes to the Danish Version of the Dutch Multifactor Fatigue Scale in Stroke Using the Three-Step Test-Interview”, nine adults with stroke were interviewed to investigate interpretative processes involved in responding to DMFS. In Paper III, “Measurement Properties of the Dutch Multifactor Fatigue Scale in Early and Late Rehabilitation of Acquired Brain Injury in Denmark”, unidimensionality, measurement invariance, and factorial structure of the original subscales were evaluated among 149 adults in rehabilitation of ABI using factor analysis. 
Joint results from both papers support validity of the subscales Impact of Fatigue, Signs and Direct Consequences of Fatigue, and Mental Fatigue. Further, they were partially invariant across early versus late rehabilitation settings. Physical Fatigue demonstrated evidence of local dependency, indicated by both interview and factor analyses. Coping with Fatigue was not unidimensional, although response processes were congruent with the intended (multifaceted) construct. Consequently, sumscores are not readily interpreted. The entire scale was multidimensional, but the original factorial structure was not adequately reproduced. Altogether, the three first-named subscales are recommended for measuring fatigue, although constructs may be overlapping. Properties of individual items is analyzed, and item revisions to the Danish translation are recommended.
Several methodological strengths and limitations are considered in the appraisal of findings, including data triangulation, sample size, and generalization. Finally, clinical implications and future perspectives for rehabilitation of fatigue following ABI are discussed, including the prospects of using DMFS as a preassessment tool for targeting EM components to individual needs.