Positive association between an estrogen receptor gene polymorphism and Parkinson's disease with dementia.

Parkinson's disease (PD) is a common cause of dementia in the elderly. Dementia in Alzheimer's disease (AD) and PD share common biologic and clinical features. The estrogen receptor (ER) gene is one of the susceptibility genes for AD. In order to test the hypothesis that the overlap between AD and PD may have a genetic basis, we determined ER gene polymorphisms in 13 PD patients with dementia (PDD) (age +/- SD; 71.9 +/- 5.5 years), 71 PD patients without dementia (PDND) (68.4 +/- 7.5 years), 86 AD patients (76.8 +/- 8.0 years) and 51 control subjects (CTL) (74.9 +/- 6.9 years). ER genotypes were classified as a P or p allele on the basis of a Pvu II-RFLP, and X and x on the basis of a Xba I-RFLP. The frequency of the P allele in the PDD group as well as the AD group was higher than that in CTL. There was no significant difference in the distribution of the P allele between CTL and PDND. There were no significant differences in the distribution of the X allele among the PDD, PDND and CTL groups, whereas a higher incidence was found in AD. We conclude that the ER gene may be a common susceptibility gene for dementia in PD as well as AD.