Ethnic differences in the frequency of β-amyloid deposition in cognitively normal individuals

We investigated which factors might explain the differences between the frequencies of brain β-amyloid (Aβ) deposition in Korean and European cognitively normal individuals (CNs). We recruited 434 Korean CNs from the Samsung Medical Center (SMC) and 323 European CNs from the US Alzheimer's Disease Neuroimaging Initiative (ADNI). The Korean CNs showed lower education duration (11.8 ± 4.8 years vs. 16.8 ± 2.5 years, p < 0.001) than the European CNs. The frequency of Aβ (+) was higher in the European CNs (32.8%) than in the Korean CNs (20.0%; p < 0.001). In the SMC genome-wide association study (GWAS), 10 variants (including rs7481773 on chromosome 11, located near the brain-derived neurotrophic factor gene) exceeded the genome-wide significance level (p < 5 × 10^-8). Especially, rs7481773 carriers showed more rapid decline in memory function than non-carriers (p = 0.048). However, this association was not observed in the ADNI GWAS. Our findings suggested that the different frequencies of Aβ (+) between CN Koreans and Europeans might be related to decreased cognitive reserve or genetic factors.