APOE and Alzheimer disease: APOE ε4 has also been found to increase the risk of dementia in pure alpha-synucleinopathies in a study where its frequency was 38% in pathologically diagnosed pure AD, 40.6% in the mixed AD and DLB group, 31.9% in pure DLB, 19.1% in Parkinson’s Disease Dementia (PDD) and 7.2% among healthy controls24.