Sleep and cognitive outcomes in multiple sclerosis; a systematic review.

BACKGROUND: Multiple sclerosis (MS) is a disabling disease of the central nervous system. People living with MS often have co-existing sleep disorders and cognitive dysfunction. The objective of this study was to scrutinize the relationship between cognitive outcomes and sleep conditions in MS. METHODS: This study followed the Joanna Briggs Institute's (JBI) and PRISMA guidelines. PubMed, Scopus, Embase, and Web of Science databases were searched and original studies delineating the relationship between sleep status and cognitive findings in MS patients| were included. The risk of bias was assessed using the JBI critical appraisal tools. RESULTS: In the final review, out of 1635 screened records, 35 studies with 5321 participants were included. Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and polysomnography were the most common assessment tools for evaluation of sleep condition, and cognitive evaluations were conducted using the tests including Paced Auditory Serial Addition Test (PASAT), California Verbal Learning Test (CVLT), Symbol Digit Modalities Test (SDMT) and Brief Visuospatial Memory Test (BVMT). Assessing the quality of studies showed no significant bias in most of the included articles. A link between sleep condition and cognitive abilities was suggested in the literature, especially with objective measurement of sleep condition; however, current evidence did not support a substantial association between self-reported sleep quality and processing speed and working memory in patients with MS. DISCUSSION: Evidence proposes sleep is an independent factor associated with cognitive outcomes in MS. Given the limitations of the evidence such as the lack of well-designed prospective studies, these findings need to be interpreted with caution.

Serum lipids and cognitive outcomes in multiple sclerosis; a systematic review and meta-analysis.

BACKGROUND: Cognitive impairment is highly prevalent in multiple sclerosis (MS) with poorly understood underlying mechanisms. Lipids are considered to be associated with MS progression through the inflammatory and oxidative stress pathways, brain atrophy, cellular signaling, and tissue physiology. In addition, serum lipids are proposed as a modifiable factor affecting the neuropsychiatric condition; therefore, this study aims to assess the association between serum lipid levels and cognitive outcomes in MS. METHODS: This study was carried out following the PRISMA 2020 statement. A systematic search was conducted in PubMed, Scopus, Web of Science, and Embase in March 2023, and the Joanna Briggs Institute (JBI)'s critical appraisal tools were utilized for risk of bias (RoB) assessments in the included studies. The quantitative synthesis was performed with the comprehensive meta-analysis (CMA3) software. RESULTS: Out of 508 screened records, 7 studies were eventually found to meet our inclusion criteria. In two studies, the course of MS in the sample of the study was only Relapsing-Remitting MS (RRMS), whereas the other five studies' sample was a combination of different phenotypes. Studies utilized different scales such as Minimal Assessment of Cognitive Function in MS (MACFIMS), Brief International Cognitive Assessment for MS (BICAMS), Montreal Cognitive Assessment (MoCA), Brief Repeatable Battery of Neuropsychological Tests (BRB-N) for cognitive evaluations. Dealing with possible confounders such as age, disease duration and level of disability was the most common possible source of bias in the included studies. One study revealed an inverse relationship between serum levels of apolipoproteins (including ApoA-I, ApoB, and ApoB/ApoA-I) and Symbol Digit Modalities Test (SDMT) scores. Also, a correlation between 24S-hydroxycholesterol (24OHC) serum concentrations and SDMT score was reported in one study. The association between serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL) and different aspects of cognitive function was reported in the studies; however, serum levels of high-density lipoprotein cholesterol (HDL) were not found to be associated. The quantitative synthesis revealed a significant correlation between TC and the MoCA scores (r =-0.238; 95 %CI: -0.366 to -0.100; p-value = 0.001); however, the correlation between TG levels and MoCA were not statistically significant (r:-0.070; 95 %CI: -0.209 to 0.072; p-value: 0.334). In addition, the mata-analyses were not associated with significant findings regarding the correlation between lipid profiles (including HDL, LDL, TG, and TC) and other cognitive assessment scales including SDMT, Brief Visuospatial Memory Test (BVMT), and California Verbal Learning Test (CVLT) (p-values>0.05). DISCUSSION: Available evidence suggested a link between TC and LDL with cognitive outcomes of MS patients which was not evident in our quantitative synthesis. The limited number of studies, high RoB, different cognitive assessment scales and reporting methods, and the cross-sectional design of the included studies, were the main limitations that alleviate the clinical significance of the findings of this study and suggested further investigations on this topic. FUNDING AND REGISTRATION: The research protocol was approved and supported by the Student Research Committee, Tabriz University of Medical Sciences (grant number: 71,909). This study is registered in the international prospective register of systematic reviews (PROSPERO ID: CRD42023441625).