APOE and Parkinson disease: Established risk factors include genetic predispositions (e.g., APOE ε4 allele and Down syndrome)28, common medical conditions (e.g., diabetes, hypertension)29,30, neurodegenerative disorders, (e.g., Parkinson's disease, Lewy body dementia)31, and nutritional deficiencies (e.g., thiamine deficiency)32.