Fatigue is common in multiple sclerosis and is associated with reduced quality of life. This study aimed to assess the correlation between fatigue scores and data from other self-assessment questionnaires, neuropsychological tests and neuroimaging, as well as data on neuroimmunological markers in cerebrospinal fluid (CSF) and serum/plasma, in clinically isolated syndrome (CIS) and relapsing remitting MS (RRMS).Modified fatigue impact scale (MFIS) scores were determined in 38 patients with newly diagnosed CIS or RRMS at baseline and after one year in a prospective longitudinal cohort study. Non-parametric correlation analyses were used to assess associations between MFIS scores and other self-assessment questionnaire data (Hospital Anxiety and Depression scale (HAD), Multiple Sclerosis Impact Scale 29 (MSIS-29) and Short Form 36 (SF-36)), as well as with neuropsychological test performances (e.g. Auditory Consonant Trigram Test (ACTT)), clinical parameters (e.g. disease duration and expanded disability status scale (EDSS)), magnetic resonance imaging (MRI) data (number of T2 lesions in brain MRI and total brain volume) and several neurodegenerative/neuroinflammatory markers in CSF and serum/plasma (IL-1β, IL-6, CXCL1, CXCL10, CXCL13, CCL-22 in plasma; neurofilament light chain (NFL) in serum; IL-6, CXCL1, CXCL10, CXCL13, CCL22, NFL and chitinase-3-like-1 (CHI3L1) in CSF. CSF and serum/plasma from 21 age- and sex-matched healthy controls were available for comparison.At both baseline and one-year follow-up, fatigue scores correlated significantly with HAD, MSIS-29 and SF-36 scores and ACTT performance (Spearman´s rho 0.45-0.78, all p ≤ 0.01) but not with the other neuropsychological test results, disease duration, EDSS ratings, number of T2 lesions, total brain volume or neurodegenerative/neuroinflammatory markers, including neurofilament light chain levels in CSF and serum. In group comparisons, MFIS scores were similar in patients fulfilling no evidence of disease activity-3 (NEDA-3) (n = 18) and patients not fulfilling NEDA-3 (n = 20) during one year of follow-up (p > 0.01).In this cohort of patients with newly diagnosed CIS and RRMS, fatigue scores were associated with mood, disease impact on daily life and quality of life as well as with alterations of attentive functions. Study results indicate that subjective fatigue scores are not well reflected by some commonly used and objectively measurable disease parameters like EDSS, T2 lesions and NFL levels.
