The behavioral variant of Alzheimer’s disease is characterized by early predominant behavioral changes, mimicking the behavioral variant of frontotemporal dementia, which is characterized by social cognition deficits and altered biometric responses to socioemotional cues. These functions remain understudied in the behavioral variant of Alzheimer’s disease. We investigated multiple social cognition components(i.e., emotion recognition, empathy, social norms and moral reasoning), using the Ekman-60-faces-test, Interpersonal-Reactivity-Index, empathy eliciting videos, Social-Norms-Questionnaire and moral dilemmas, while measuring eye-movements and galvanic skin response. We compared 12 patients with the behavioral variant of Alzheimer’s disease with patients with the behavioral variant of frontotemporal dementia(n = 14), typical Alzheimer’s disease(n = 13) and individuals with subjective cognitive decline(n = 13), using ANCOVAs and age and sex adjusted post hoc testing. Patients with the behavioral variant of Alzheimer’s disease(40.1 ± 8.6) showed lower scores on the Ekman-60-faces-test compared to individuals with subjective cognitive decline(49.7 ± 5.0, p < 0.001), and patients with typical Alzheimer’s disease(46.2 ± 5.3, p = 0.05) and higher scores compared to patients with behavioral variant of frontotemporal dementia(32.4 ± 7.3, p = 0.002). Eye-tracking during the Ekman-60-faces-test revealed no differences in dwell time on the eyes(all p > 0.05), but patients with the behavioral variant of Alzheimer’s disease(18.7 ± 9.5%) and frontotemporal dementia(19.4 ± 14.3%) spent significantly less dwell time on the mouth than individuals with subjective cognitive decline(30.7 ± 11.6%, p < 0.01) and patients with typical Alzheimer’s disease(32.7 ± 12.1%, p < 0.01). Patients with the behavioral variant of Alzheimer’s disease(11.3 ± 4.6) exhibited lower scores on the Interpersonal-Reactivity-Index compared with individuals with subjective cognitive decline(15.6 ± 3.1, p = 0.05) and similar scores to patients with the behavioral variant of frontotemporal dementia(8.7 ± 5.6, p = 0.19) and typical Alzheimer’s disease(13.0 ± 3.2, p = 0.43). The galvanic skin response to empathy eliciting videos did not differ between groups(all p > 0.05). Patients with the behavioral variant of Alzheimer’s disease(16.0 ± 1.6) and frontotemporal dementia(15.2 ± 2.2) showed lower scores on the Social-Norms-Questionnaire than patients with typical Alzheimer’s disease(17.8 ± 2.1, p < 0.05) and individuals with subjective cognitive decline(18.3 ± 1.4, p < 0.05). No group differences were observed in scores on moral dilemmas(all p > 0.05), while only patients with the behavioral variant of frontotemporal dementia(0.9 ± 1.1) showed a lower galvanic skin response during personal dilemmas compared with subjective cognitive decline(3.4 ± 3.3 peaks per minute, p = 0.01). Concluding, patients with the behavioral variant of Alzheimer’s disease showed a similar though milder social cognition profile and a similar eye-tracking signature to patients with the behavioral variant of frontotemporal dementia and greater social cognition impairments and divergent eye-movement patterns compared with patients with typical Alzheimer’s disease. Our results suggest reduced attention to salient facial features in these phenotypes, potentially contributing to their emotion recognition deficits.

Background: Limited literature exists regarding the clinical features of end stage behavioral variant frontotemporal dementia (bvFTD). This data is indispensable to inform and prepare family members as well as professional caregivers for the expected disease course and to anticipate with drug-based and non-pharmacological treatment strategies. Objective: The aim of the present study was to describe end stage bvFTD in a broad explorative manner and to subsequently evaluate similarities and dissimilarities with the end stage of the most prevalent form of young-onset dementia, Alzheimer’s disease (yoAD). Methods: We analyzed medical files on patients, using a mixed model of qualitative and quantitative approaches. Included were previously deceased patients with probable bvFTD and probable yoAD. End stage was defined as the last 6 months prior to death. Primary outcome measures comprised somatic, neurological, and psychiatric symptoms and the secondary outcome measure was cause of death. Results: Out of 89 patients, a total of 30 patients were included (bvFTD; n = 12, yoAD; n = 18). Overall, the end stages of bvFTD and yoAD were characterized by a broad spectrum of clinical symptoms including severe autonomic dysfunction and an increased muscle tone. Patients with bvFTD displayed more mutism compared with yoAD while compulsiveness was only present in bvFTD. Conclusion: Our study describes the full clinical spectrum of end stage bvFTD and yoAD. In this study, symptoms extend far beyond the initial behavioral and cognitive features. By taking both somatic, psychiatric, and neurological features into account, family members and professional caregivers may anticipate (non) pharmacological treatment.