Association analyses of apolipoprotein E genotypes and cognitive performance in patients with Parkinson's disease

Background Cognitive impairment is a common non-motor symptom of Parkinson's disease (PD). The apolipoprotein E (APOE) epsilon 4 genotype increases the risk of Alzheimer's disease (AD). However, the effect of APOE epsilon 4 on cognitive function of PD patients remains unclear. In this study, we aimed to understand whether and how carrying APOE epsilon 4 affects cognitive performance in patients with early-stage and advanced PD.Methods A total of 119 Chinese early-stage PD patients were recruited. Movement Disorder Society Unified Parkinson's Disease Rating Scale, Hamilton anxiety scale, Hamilton depression scale, non-motor symptoms scale, Mini-mental State Examination, Montreal Cognitive Assessment, and Fazekas scale were evaluated. APOE genotypes were determined by polymerase chain reactions and direct sequencing. Demographic and clinical information of 521 early-stage and 262 advanced PD patients were obtained from Parkinson's Progression Marker Initiative (PPMI).Results No significant difference in cognitive performance was found between ApoE epsilon 4 carriers and non-carriers in early-stage PD patients from our cohort and PPMI. The cerebrospinal fluid (CSF) Amyloid Beta 42 (A beta 42) level was significantly lower in ApoE epsilon 4 carrier than non-carriers in early-stage PD patients from PPMI. In advanced PD patients from PPMI, the BJLOT, HVLT retention and SDMT scores seem to be lower in ApoE epsilon 4 carriers without reach the statistical significance.Conclusions APOE epsilon 4 carriage does not affect the cognitive performance of early-stage PD patients. However, it may promote the decline of CSF A beta 42 level and the associated amyloidopathy, which is likely to further contribute to the cognitive dysfunction of PD patients in the advanced stage.