The cognitive-behavioral missing link in myotonic dystrophy type 1: Rethinking social cognition assessment

Background Myotonic dystrophy type 1 (DM1) is associated with central nervous system involvement and cognitive–behavioral alterations, including deficits in social cognition. However, standard neuropsychological assessments based on accuracy may underestimate clinically relevant dysfunction. Objectives To determine whether task completion times provide a more sensitive index of social-cognitive performance than accuracy-based metrics in DM1. Methods Thirty-three individuals with genetically confirmed DM1 and 40 healthy controls completed the Reading the Mind in the Eyes Test (RMET) and the Story-Based Empathy Test (SET). Both accuracy and task completion times were analyzed. Executive functions and processing speed were evaluated using standard neuropsychological measures. Group comparisons and regression analyses were performed adjusting for age, education, and executive performance. Results DM1 patients showed different patterns for accuracy and completion time across social-cognitive tasks. RMET accuracy was reduced, whereas SET accuracy was comparable between groups. In contrast, completion times were consistently prolonged across all social-cognition tasks in DM1. These differences remained significant after controlling for executive function. SET completion time showed stronger discriminative performance than SET accuracy measures, whereas RMET completion time and accuracy showed comparable discriminative performance. Conclusions Social cognition in DM1 is characterized by prolonged completion times, while accuracy is relatively preserved on several measures. This discrepancy suggests that conventional accuracy-based assessments may not fully capture subtle differences in social-cognitive performance. Temporal metrics may reveal aspects of social cognition performance not detected by accuracy-based assessments alone and contribute to a more comprehensive neuropsychological evaluation.