APOE4 Allele, Sex, and Dementia Risk in Parkinson's Disease: Lessons From a Longitudinal Cohort.

Introduction: The effect of APOE4 allele on dementia risk is well established in Alzheimer's disease and Parkinson's disease (PD). However, it is unknown if sex modifies this relationship. We sought to determine the effect of sex on the relationship between APOE4 status and incident cognitive decline in PD.

Methods: Data from the prospectively collected longitudinal National Alzheimer's Coordinating Center (NACC) Uniform Data Set (UDS) and Neuropathology Data Set (NDS) were analyzed. The NACC develops and maintains data from approximately 29 National Institutes of Aging-funded Alzheimer's Disease Research Centers. Further details may be found at the NACC web site (www.alz.washington.edu). The visit at which diagnosis of PD was made was termed the baseline visit. All patients with a PD diagnosis but without dementia at the baseline visit were included in the analyses.

Results: Presence of APOE4 allele was associated with higher odds (OR = 7.4; < .001) of subsequent diagnosis of dementia and with a faster time to developing dementia ( = .04). Those with APOE4 allele were more likely to have neuropathology associated with Alzheimer's disease than those without APOE4 allele. We did not find any difference by sex. There were no differences between Lewy body pathology or neuron loss in the substantia nigra between the 2 groups. Sex was not associated with dementia risk in PD (OR = 0.53, = .15) or with the time to dementia onset ( = .22). Sex did not modify the relationship between the APOE4 allele and dementia onset in PD patients ( = .12).

Conclusions: APOE4 allele status in PD may be a predictor of cognitive decline in PD but does not appear to be modified by sex.