The Comorbidity of AD and PD: Exploring Clinical, Pathological, and Biomarker Interactions

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative disorders, primarily characterized by cognitive decline and motor dysfunction, respectively. The comorbidity of AD and PD further increases disease complexity and presents significant challenges for clinical diagnosis and treatment. Due to substantial clinical overlaps in the advanced stage of AD and PD, comorbid cases are frequently misdiagnosed as a single disease, which hinders early recognition and timely intervention. Based on pathological observations from patients with comorbidity of AD and PD, this review discusses the prevalence and clinical features of AD-PD comorbidity, the spatiotemporal progression and potential interactions of key pathological proteins, including β-amyloid (Aβ), phosphorylated tau (pTau), and α-synuclein (α-syn). The aim of this review is to update potential new insights and strategies to improve diagnostic accuracy, advance personalized therapeutic approaches, and guide future research into the underlying mechanisms of comorbidity.