Relationship between sleep disorders and information processing speed in multiple sclerosis

Objectives: It is estimated that up to 65 % of pwMS (people with multiple sclerosis) experience varying degrees of cognitive impairment, the most commonly affected domain being Information Processing Speed (IPS). As sleep disturbance is a predictor of detriments in IPS, the authors aimed to study the association between the severity of Restless Legs Syndrome (RLS) and Obstructive Sleep Apnea (OSA) symptoms with IPS in pwMS. Methods: In a cross-sectional study, the authors enrolled people with relapsing-remitting and secondary progressive MS referred to the comprehensive MS center of Kashani Hospital in Isfahan, Iran. The authors used Berlin and STOP-Bang questionnaires for assessing OSA symptoms, and the International Restless Legs Syndrome Study Group (IRLSSG) scale for the presence and severity of symptoms of RLS. The authors used the Integrated Cognitive Assessment (ICA) test, a language and education-independent tool, to assess visual processing speed. Results: The authors included 211 pwMS, with a mean age of 36.73 +/- 8.9 (81.9 % female). PwMS with higher RLS scores showed lower IPS, with ICA indexes of 0.66 +/- 0.09 vs. 0.61 +/- 0.12 in low- and high-risk RLS groups, respectively (p < 0.01). There were no significant associations between IPS as measured by the ICA index and OSA symptom severity. Conclusion: The authors found impairments in IPS in pwMS to be linked with the severity of RLS symptoms, but not with OSA. Considering the high prevalence and underdiagnosis of RLS in pwMS, and the profound impact of IPS on quality of life, this association highlights the importance of screening and treating RLS in this population.