Introduction: Emotional issues are often reported among individuals with myotonic dystrophy type 1 (DM1) and some studies have suggested that deficits in ability to quickly encode emotions may contribute to these problems. However, poor performance on emotion encoding tasks could also be explained by a more general cognitive deficit (Full Scale IQ [FSIQ]), rather than a specific deficit in emotional processing. Since individuals with DM1 are known to exhibit difficulties in general cognitive abilities, it is important to account for FSIQ when evaluating emotion encoding. The aim of this study was to compare emotion encoding abilities between individuals with and without DM1, while adjusting for the impact of general cognitive abilities (FSIQ). Methods: The sample included 35 individuals with adult-onset DM1 and 54 unaffected adults who completed assessments of emotion encoding abilities (Ekman faces test) and general cognitive abilities (Wechsler Adult Intelligence Scale-IV). Performance on the emotion encoding task was operationalized as proportion correct and response time. Group differences in proportion correct were evaluated with generalized linear regression, while linear regression models were used to determine the effect of group on response time. Models were adjusted for age, sex, and FSIQ. The false discovery rate (FDR) was applied to control false positives due to multiple comparisons (pfdr ). Results: No significant group differences were observed for emotion encoding abilities (all pfdr > 0.13). FSIQ was significantly associated with proportion correct and with response time (all pfdr < 0.05). Conclusions: Emotion encoding appears intact in individuals with DM1 and variation in the ability to encode facial expressions was associated with FSIQ. Further research is required to address the relationship between general cognitive abilities and emotion encoding abilities among DM1 patients.
Keywords: Myotonic dystrophy type 1; cognition; emotion encoding; emotion recognition; general intelligence.