Lower prevalence of cognitive impairment in a specific MS population: associated factors and probable reasons

Introduction: Multiple Sclerosis (MS) symptoms vary according to the affected brain topography and can cause cognitive dysfunction, a common cause of limitations in everyday life and highly associated with the risk of ongoing disability. 

Objectives: To assess the frequency of cognitive impairment (CI) in MS patients and their association with other variables of interest.

Methods: In this cross-sectional study we applied the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) as cognitive measurement. It was considered CI when test performance of an individual falls by 1.5 Standard Deviation (SD) in relation to normative values. Statistical associations were performed with: age, sex, years of education, disease duration, previous relapse number, brain lesional load, Expanded Disability Status Scale (EDSS), Modified Fatigue Impact Scale (MFIS), Multiple Sclerosis Impact Scale (MSIS-29), and Hospital Anxiety and Depression Scale (HADS).

Results: 98 subjects were included in the study (78.9% female, mean age 39.0 ± 9.8 years, median disease duration 7.6 years (IQR=4.3-11.0), median EDSS 2.0 (IQR=2.0-3.0). Mean processing speed Z-core was -0.18, with 4.1% <1.5 SD, mean verbal memory Z-score was -0.60, with 17.3% <1.5 SD, mean visual memory Z-score was -0,16, with 9.2% <1.5 SD. Worse processing speed scores were found in progressive phenotypes. Significant correlations between visual memory and EDSS (r=-0.324; p=0.002) and processing speed and EDSS (r=-0.298; p=0.004) were identified. No significant BICAMS Z-score tests associations were observed with age, sex, education, disease duration, previous relapse number, lesional load, MFIS, MSIS-29 and HADS scores.

Conclusions: The findings pointed to a lower frequency of CI (up to 17.3%) in our study, as compared to classical cohorts previously described. This result may be related to early treatment in the current era, access to health resources, shorter duration of disease, and probably to a higher cognitive reserve in our sample.