Comment: Epidemiology of dementia with Lewy bodies—The Alzheimer-Parkinson overlap

Dementia with Lewy bodies (DLB) is viewed by many as a condition that combines features of Alzheimer disease (AD) and Parkinson disease (PD). Autopsy in DLB discloses both amyloid and synuclein deposition, and the relative degree of each may determine the clinical phenotype.¹ Despite being the second most common form of dementia, risk factors of DLB have never been systematically studied. The current report by Boot et al.² therefore represents a considerable advance. Relying on data from 3 separate cohorts, the authors found that the risk factor profile of DLB appeared to combine aspects of AD and PD. Known risk factors for PD, such as nonuse of caffeine, anxiety, depression, and family history of PD were present in DLB. Similarly, AD risk factors such as APOE status, depression, and stroke were also present in DLB. Smoking, a protective factor for PD and a risk factor for AD, was not associated with DLB, perhaps suggesting that the risk factors “canceled out.” However, when risk factors were common between conditions (depression and caffeine use), the relationship in DLB appeared to be stronger than for AD or PD individually, suggesting additive risks. Although the risk factors were not always comprehensively assessed and diagnosis was clinical in the majority of cases (albeit with broadly similar results in the subgroup with autopsy confirmation), the study is well-designed and comprehensively analyzed. In addition to providing for the first time a broad picture of risk factors for DLB, the study reinforces the close interactions among DLB, PD, and AD, and points to the potential importance of multiple interacting pathologies in determining clinical disease.