Objective: Fatigue is one of the most frequent sequelae of traumatic brain injury (TBI), although its causes are poorly understood. This study investigated the interrelationships between fatigue and sleepiness, vigilance performance, depression, and anxiety, using a structural equation modeling approach.
Methods: Seventy-two participants with moderate to severe TBI (78% males) were recruited a median of 305 days postinjury. They completed the Fatigue Severity Scale, a vigilance task, the Epworth Sleepiness Scale, and Hospital Anxiety and Depression Scale. A model of the interrelationships between the study variables was developed, tested, and modified with path analysis.
Results: The modified model had a good overall fit (χ22 = 1.3, P = .54; comparative fit index = 1.0; root-mean square error of approximation = 0.0; standardized root-mean square residual = 0.02). Most paths in this model were significant (P < .05). Fatigue predicted anxiety, depression, and daytime sleepiness. Depression predicted daytime sleepiness and poor vigilance, whereas anxiety tended to predict reduced daytime sleepiness.
Conclusions: This model confirms the complexity of fatigue experience. It supports the hypothesis that fatigue after TBI is a cause, not a consequence, of anxiety, depression, and daytime sleepiness, which, in turn (especially depression), may exacerbate fatigue by affecting cognitive functioning. These findings suggest that to alleviate fatigue, it is important to address each of these factors. However, the findings need to be confirmed with a longitudinal research design.
School of Psychological Sciences, Monash University, Clayton, Victoria, Australia (Drs Ponsford, Schönberger, and Rajaratnam); Monash-Epworth Rehabilitation Research Centre, Epworth Hospital, Melbourne, Victoria, Australia (Drs Ponsford and Schönberger); and Department of Rehabilitation Psychology and Psychotherapy, Institute of Psychology, University of Freiburg, Freiburg im Breisgau, Germany (Dr Schönberger).
Corresponding Author: Jennie Ponsford, PhD, School of Psychological Sciences, Monash University, Clayton 3800, Victoria 3121, Australia (email@example.com).
This work was supported by the National Health and Medical Research Council (project ID 334002) and Monash University. The authors acknowledge the contributions of Monique Roper to data collection for this study and Carlo Ziino for design of the vigilance task.
Jennie Ponsford has received royalties from Psychology Press and Guilford Press for textbooks on traumatic brain injury, has received an honorarium, travel, and accommodation support to present a lecture on fatigue and sleep disturbance at the TBI Interagency Conference in Washington, District of Columbia, May 2011. Michael Schönberger reports no conflicts of interest. Shantha Rajaratnam has served as a consultant through his institution to Vanda Pharmaceuticals, Philips Respironics, EdanSafe, The Australian Workers' Union, and National Transport Commission and has through his institution received research grants and/or unrestricted educational grants from Vanda Pharmaceuticals, Takeda Pharmaceuticals North America, Philips Lighting, Philips Respironics, Cephalon, and ResMed Foundation and reimbursements for conference travel expenses from Vanda Pharmaceuticals. His institution has received equipment donations or other support from Optalert, Compumedics, and Tyco Healthcare. He has also served as an expert witness and/or consultant to shift work organizations.
The authors declare no conflicts of interest.