Fatigue is a frequent and severe symptom in stroke survivors, associated with poorer physical health, reduced quality of life and even increased mortality. Although post-stroke fatigue (PSF) is common and disabling, there is no consensus on definition, evaluation methods or interventions. Furthermore, the underlying mechanisms of PSF and the significance of different biopsychosocial factors in PSF development are not fully elucidated.
The overall aim of this thesis was to increase the knowledge about assessment, trajectories and associated factors of PSF to establish a better knowledge base for developing treatment strategies aiming at ameliorating PSF. The work is based on two longitudinal observational studies. In the first study, displayed in paper I, trajectories of PSF through the first 18 months post-stroke were investigated. The second study yielded the data for paper II and III. In paper II the overlap and differences in prevalence-estimates in fatigue-caseness using the Fatigue Severity Scale, the Fatigue Questionnaire and the Lynch Interview at one time-point in a sample of stroke-patients was explored. In addition, we investigated how PSF measured with these instruments were associated with different predictor-variables. In paper III, the associations of demographic, medical and symptom-related factors with PSF in the acute phase, at three and twelve months post-stroke were explored.
The first aim of the thesis was to explore whether subgroups of stroke survivors with distinct trajectories could be identified using Growth Mixture Modeling and secondly whether these subgroups differed on sociodemographic, medical and symptom-related characteristics. Paper I displays three distinct trajectories of PSF from the acute phase to 18 months post stroke, namely courses displaying low, medium and high fatigue. Belonging to the high fatigue-class was associated with pre-stroke fatigue, multiple comorbidities and not working. Belonging to a low fatigue-class was associated with few symptoms of depression and being more independent in personal activities of daily living.
Paper II displays a vast variance in prevalence of fatigue-cases in the same sample at the same time-point depending on which of three instruments was used to assess fatigue symptoms and cases. There was also a variance in the associations between being a fatigue-case and the analyzed predictor variables using the different instruments, probably reflecting that they cover slightly different aspects of the PSF-experience. In paper III, the associations of demographic, medical and symptom-related factors with PSF at different time-points were explored. The findings suggest that PSF may be triggered, maintained or worsened by stroke-related impairments, psychological distress and/or maladaptive coping strategies. Furthermore, we found that significant PSF also occur in patients with minor stroke-sequelae.
In summary, this thesis gives insights into different trajectories of fatigue post-stroke. It also expands on current knowledge about which factors may serve as protective against PSF-development and which factors may render stroke survivors vulnerable for developing PSF, hereby suggesting possible targets for development of interventions aimed at ameliorating PSF. A special awareness should be on patients with minor stroke-sequale as they may have unmet need for follow-up, increasing the risk of PSF-development. The results in this thesis also demonstrate how different methodology yields a wide variance in identification of fatigue-cases, underscoring the importance of reaching a consensus on how to measure fatigue. Correct identification of fatigue-cases is crucial for understanding fatigue, its causes and for development of empirically based interventions. Further studies are warranted in larger samples, preferably multicenter studies, to allow for necessary increase in the sample size, to achieve consensus on how to measure fatigue. Methods should include a wide array of measurements, reflecting a biopsychosocial understanding of fatigue