Social Cognitive Impairment in Early Parkinson’s Disease: a novel “Mild Impairment”?

Abstract Introduction Growing evidence highlighting a social cognition (SC) deficit in Parkinson’s disease (PD) have recently emerged, while pointing to ambiguous findings. Our objective was to determine if SC abilities impairment is frequent at the early stages of PD. Methods 109 patients with idiopathic PD diagnosed within the past four years (ICEBERG cohort) and 39 healthy participants were enrolled in this study. SC was evaluated using the Mini-Social Cognition and Emotional Assessment (Mini-SEA), that allows a multi-domain assessment of SC. Relationships between SC and clinical characteristics, global cognitive efficiency, mood, anxiety, apathy and impulse control disorders, were also evaluated. Results 30% of the cohort of patients was significantly impaired on the socio-emotional assessment. Further, SC deficit in isolation (20.2% of the cohort) was 3.5 times more frequent than a Mild Cognitive Impairment in isolation (5.5%). Both emotion identification and Theory of Mind were impaired compared to healthy participants. No effect of age, level of education, disease severity or dopamine replacement therapy, and global cognitive efficiency were found. Only scores on the Frontal Assessment Battery were correlated with the SC abilities. Conclusion SC impairment is frequent in early PD and should be given more consideration. It is commonly observed in the absence of any other cognitive disorder and may represent the most common neuropsychological deficit at the early stages of PD. In line with the definition of MCI criteria, we suggest highlighting the presence of a sixth MCI subtype and naming it the "Mild Social Cognition Impairment (MSCI)".