Cognitive, neuropsychiatric, and motor features associated with apolipoprotein E ε4 allele in a sample of Bulgarian patients with late-onset Parkinson's disease.

OBJECTIVE: To evaluate the role of apolipoprotein E (APOE) ε4 allele on cognitive, neuropsychiatric, and motor features in a sample of Bulgarian patients with late-onset Parkinson's disease (LOPD, age at onset > 55 years). METHODS: A total of 16 patients with LOPD having APOE ε3/ε4 genotype were compared to 30 patients with LOPD having APOE ε3/ε3 genotype and 20 healthy control individuals. Detailed cognitive assessment and evaluation of neuropsychiatric and motor symptoms were performed. RESULTS: The patients with LOPD had significantly lower scores in all cognitive domains compared to controls. The patients with LOPD carrying an ε4 allele showed some significant differences in their cognitive, motor, and neuropsychiatric features. CONCLUSIONS: The data suggest a role of the APOE genotype as a disease-modifying factor.