Association between apolipoprotein E genotypes and Parkinson's disease.

Previous studies on the association between apolipoprotein E (APOE) alleles and Parkinson's disease (PD) have shown contradictory results. A recent study showed that APOE is involved in a molecular pathway of α-synuclein-induced neurodegeneration. We therefore conducted the first Thai study on APOE genotypes in patients with PD. We analysed the frequencies of APOE genotypes in our case-control study of 155 patients with sporadic PD and 158 control participants. We identified a higher frequency of the APOE-ε2 allele among patients with PD than among controls (odds ratio=2.309, 95% confidence interval=1.111-4.799). Genetic association is a powerful tool for detecting disease susceptibility alleles, but there are many pitfalls to consider before claiming any association. The discrepancy among the results of the genetic association studies of APOE genotypes as a risk of susceptibility to PD emphasises that this association merits clarification by the study of a single large homogeneous population.