People with Multiple Sclerosis (PwMS) and healthy controls (HCs) were evaluated on cognitive variability indices and we examined the relationship between fatigue and cognitive variability between these groups. Intraindividual variability (IIV) on a neuropsychological test battery was hypothesized to mediate the group differences expected in fatigue.

Fifty-nine PwMS and 51 HCs completed a psychosocial interview and battery of neuropsychological tests and questionnaires during a 1-day visit. Fatigue in this study was measured with the Fatigue Impact Scale (FIS), a self-report multidimensional measure of fatigue. IIV was operationalized using two different measures, a maximum discrepancy score (MDS) and intraindividual standard deviation (ISD), in two cognitive domains, memory and attention/processing speed. Two mediation analyses with group (PwMS or HCs) as the independent variable, variability composite (memory or attention/processing speed) measures as the mediators, total residual fatigue (after accounting for age) as the outcome, and depression as a covariate were conducted. The Baron and Kenny approach to testing mediation and the PROCESS macro for testing the strength of the indirect effect were used.

Results of a mediation analysis using 5000 bootstrap samples indicated that IIV in domains of both attention/processing speed and memory significantly mediated the effect of patient status on total residual fatigue.

IIV is an objective performance measure that is related to differences in fatigue impact between PwMS and HCs. PwMS experience more variability across tests of attention/processing speed and memory and this experience of variable performance may increase the impact of fatigue.

多发性硬化症患者 (PwMS) 和健康对照组 (HCs) 的认知变异性指数进行了评估，我们检查了这些组之间疲劳和认知变异性之间的关系。假设神经心理学测试电池上的个体内变异性 (IIV) 可以调节疲劳中预期的组差异。

在为期 1 天的访问中，59 名 PwMS 和 51 名 HC 完成了社会心理访谈以及一系列神经心理学测试和问卷调查。本研究中的疲劳是用疲劳影响量表 (FIS) 测量的，这是一种自我报告的多维疲劳测量方法。IIV 在两个认知领域、记忆和注意力/处理速度中使用两种不同的测量方法进行操作，即最大差异评分 (MDS) 和个体内标准差 (ISD)。以组（PwMS 或 HCs）作为自变量、可变性复合（记忆或注意力/处理速度）测量作为中介、总残余疲劳（考虑年龄后）作为结果以及抑郁作为协变量进行了两项中介分析.

使用 5000 个引导样本的中介分析结果表明，IIV 在注意力/处理速度和记忆力方面显着调节了患者状态对总残余疲劳的影响。

IIV 是一种客观的性能指标，与 PwMS 和 HC 之间的疲劳影响差异有关。PwMS 在注意力/处理速度和记忆力的测试中经历了更多的可变性，这种可变性能的体验可能会增加疲劳的影响。