There is some disagreement between clinical and basic science as to the benefit of estrogen in preventing cognitive decline. For cardiovascular disease, estrogen effects have been shown to vary with estrogen receptor (ESR) genotype. The present study was conceived to review evidence of ESR association with Alzheimer's disease (AD) which could account for the variability observed in estrogen treatment outcome.A meta-analysis was performed on data from 8288 cases and controls, controlling for ethnicity (Asian vs European). To explore the specificity of our findings further, a second meta-analysis of association studies was then appended, addressing non-AD forms of dementia or cognitive impairment (total n=11036).A significant overall association of AD with two neighboring ESR1 variants located in a transcription-enhancing region (p=0.015) was noted. The genotypic effect was driven by the minor alleles in Asian populations, and did not reach significance in European samples (OR=1.1, p>0.267). When the phenotype was extended to other forms of dementia or cognitive impairment, the association was no longer observed.ESR1 variability was confirmed to modulate susceptibility to AD in Asian individuals, but not in Europeans. More research is required to address possible clinical implications, e.g., for hormone replacement therapy in early stages of AD.