Cognitive impairment at diagnosis predicts 10-year multiple sclerosis progression

Background: Cognitive impairment occurs from the early phases of multiple sclerosis (MS), and more frequently affects secondary progressive (SP) subjects than relapsing-remitting (RR). Objective: To investigate relationships between cognitive dysfunctions in newly diagnosed RRMS, and long-term MS-related outcomes. Methods: The present 10-year retrospective longitudinal study included 155 RRMS subjects, tested with the Rao Brief Repeatable Battery at MS diagnosis. The reaching of Expanded Disability Status Scale (EDSS) 4.0, and the SP conversion were recorded. Results: 67 subjects (43.2%) reached EDSS 4.0, and 34 subjects (21.9%) converted to SP during a follow-up period of 10.0 +/- 1.8 years. Subjects with cognitive impairment at diagnosis had a rate of reaching EDSS 4.0 more than three times greater (p<0.001; HR=3.183), and a rate of SP conversion more than two times greater, as compared to cognitively preserved subjects (p=0.008; HR=2.535). In particular, better scores in the Selective Reminding Test-Delayed Recall and in the Symbol Digit Modalities Test at baseline were associated with lower SP conversion rates during the follow-up period (p=0.018; HR=0.835; and p=0.001; HR=0.941, respectively). Conclusion: Cognitive impairment, with particular involvement of processing speed and memory, predicts disability progression and SP conversion in newly diagnosed RRMS, highlighting the importance of cognitive assessment from the beginning of MS.