Modulation of the age at onset of Parkinson's disease by apolipoprotein E genotypes.

Parkinson's disease (PD) patients often develop dementia, and Alzheimer's disease (AD) patients frequently develop parkinsonian signs. The apolipoprotein E epsilon4 allele is associated with increased risk and earlier onset of AD. We studied 137 unrelated white PD patients. Those with epsilon4 had the earliest onset (52.7 +/- 9.8 years), epsilon3/epsilon3 patients had an intermediate onset (56.1 +/- 11.1 years), and those with epsilon2 had the latest onset (59.1 +/- 13.4 years). The age at onset distribution for epsilon4/epsilon- was significantly earlier than for epsilon3/epsilon3 and epsilon2/epsilon3. These preliminary results suggest that apolipoprotein E genotypes modulate the age at onset of PD.