Abstract
Fatigue is one of the most debilitating symptoms of Multiple Sclerosis (MS). The importance of fatigue management to quality of life, and challenges in measuring this construct, suggest a need to better understand and assess fatigue. The measurement of fatigue has historically been comprised of self-report scales, but recent research literature has begun reporting attempts to objectively measure fatigue using performance during sustained cognitive tasks, such as the Paced Auditory Serial Addition Test (PASAT) and the Symbol Digit Modalities Test (SDMT). However, there has yet to be a consensus as to whether these objective measures of fatigue concur with more traditional subjective approaches. The current meta-analysis was conducted to evaluate the relationship between these two fatigue measurement approaches and determine whether expected moderators (e.g., demographic, clinical, and measure type variables) affected the strength of this association. Following a literature search and contacting authors for necessary data, 66 eligible studies were identified with 106 effects that were utilized in the main analyses. A three-level random-effects model revealed a significant overall small effect ( r = .19, 95% CI [0.16 to 0.23]). Age, race, education, disease severity, disease duration, and type of fatigue assessment used (objective or subjective) did not significantly moderate this main effect. While MS subtype did not reach the level of significance as a moderator, it revealed a positive effect that is important to consider conceptually and to avoid Type II error. However, sex was a significant moderator, such that studies involving more females had stronger associations. Results corroborate limited previous findings of a significant, but small, relationship between subjective and objective measurements of fatigue, but also suggest further investigation is needed in considering fatigue construct definitions and assessment within the context of these significant moderators. Findings have important clinical and research implications for improving assessment of fatigue and improving current treatment approaches in MS samples, as well as other populations that suffer from fatigue.