Among patients with multiple sclerosis (MS), cognitive reserve (CR) and brain reserve (BR) may moderate the effect of gray matter atrophy on classic and social cognition, respectively, with greater protective effects seen in early stages of MS, according to study results published in Multiple Sclerosis and Related Disorders.
Previous studies have focused on cognitive deficits in classic domains, including complex attention, working memory, information processing speed, learning and executive functions. However, limited data are available on social cognition in patients with MS. The objective of the current cross-sectional study was to determine the impact of CR and BR on social cognition in patients with MS.
The study sample included 60 patients with MS (age, 18-55 years) and 60 age-, sex-, and education-matched healthy controls. Of these, 34 patients with MS (56.7%) were cognitively impaired.
All participants underwent clinical assessment and detailed neurologic examination, a battery of neuropsychological testing, as well as Theory of Mind (ToM) testing, defined as the ability to infer other persons’ mental states and predict behavior. In addition, all participants completed a 3Tesla brain MRI. Study researchers assessed patients’ cortical and subcortical gray matter volume. Assessment of CR was determined based on education, while intracranial volume (ICV) was used as a proxy of BR.
Participants with MS had lower scores compared with those in the healthy control group on both tasks of ToM: Eye Test (58.7% vs 81.9%, respectively; P <.001) and Videos Test (75.3% vs. 88.1%, respectively; P <.001).
Total gray matter volume (37.6 vs 39.8, respectively; P <.001), cortical gray matter volume (28 vs. 29.4; P = .002), subcortical gray matter volume (3.40 vs 3.80, respectively; P <.001), and white matter volume (28.0 vs 29.8, respectively; P <.001) were lower in patients with MS, compared with those in the healthy controls group. Among patients in both groups there was no correlation between education and ICV.
According to the statistical analysis, education was an independent predictor of overall cognitive status. Patients with higher education had better cognitive status (R2, 0.088; P =.005). There was a significant interaction between education and subcortical gray matter volume (R2, 0.219; P < .001), as higher education reduced the negative impact of gray matter atrophy on cognitive function.
Additionally, there was a significant interaction between ICV and cortical gray matter volume, as a larger ICV was associated with superior performance in social cognitive tests, moderating the negative effects of cortical GM atrophy on these. However, CR had no significant effect.
The protective effect of education and ICV was indicated in early stages of disease, mostly in patients with less than 10 years of disease duration.
The study had several limitations, including its cross-sectional design, the use of proxies to assess reserve, and the assessment of social cognitive based on tests that were not validated specifically for patients with MS.
“The results obtained in the present study confirm that CR and BR both have protective roles on cognition in MS patients, moderating the negative effect of GM [gray matter] atrophy,” concluded the study researchers.
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Machado R, Lima C, d’Almeida OC, et al. Protective effects of cognitive and brain reserve in multiple sclerosis. Mult Scler Relat Disord. Published online December 26, 2020. doi:10.1016/j.msard.2020.102716