Characterising the prodromal phase in dementia with Lewy bodies

Introduction: Three presentations of prodromal dementia with Lewy bodies (DLB) have recently been proposed. This study investigates the frequency of symptoms in the prodromal phase of DLB. Method: Patients diagnosed with DLB between the 1^st of February 2017 and 1^st of February 2021 were retrospectively identified and matched to a group of patients diagnosed with Alzheimer's disease (AD). Patient case files were reviewed identifying the first symptoms and symptoms in the prodromal phase (cognitive impairment, psychiatric symptoms, delirium/acute confusional episodes, RBD, motor symptoms indicative of Parkinson's disease, anosmia, and autonomic dysfunction). Results: A total of 166 DLB patient and 168 AD patients were included. Of the proposed presentations in patients diagnosed with DLB, 30% presented with cognitive impairment at onset in isolation, 6% with psychiatric symptoms, and 2% with delirium/acute confusional episodes. Prodromal DLB was more likely to present with no cognitive symptoms at initial presentation (38% vs 10%) and was more likely to involve other symptoms (69% vs 26%). Of other possible presentations, Rapid eye-movement sleep Behaviour Disorder (RBD) was found at onset in 22% with a mean prodromal length of 8.4 years (all symptoms: mean 4.3 years, SD 5.8). Conclusion: We found some supportive evidence of the proposed cognitive and psychiatric presentations of prodromal DLB. Our findings build on previous findings that an RBD presentation exist, and further research is needed to characterise this presentation.