Frequency of preclinical Alzheimer's disease in Japanese clinical study settings: a meta-analysis

BackgroundMany of earlier studies reporting the frequency of preclinical Alzheimers disease (AD) among cognitive normal (CN) individuals have based on the clinical study cohort from Western countries, and it has not been validated whether the frequency of preclinical AD in Asian country cohort may differ from that in Western countries. MethodsWe conducted meta-analysis of earlier literature and original data of 4 Japanese cohort study (i.e., AMED-Preclinical, Brain/Minds Aging Imaging Study, J-ADNI, and A4 study screening conducted in Japan), among which we incorporated cognitive normal (CDR = 0) clinical study participants who were examined their amyloid status by amyloid-PET or CSF. ResultsIn total, among the reviewed 658 Japanese CN participants from 10 different groups, 103 turned out to be amyloid positive, and the estimated overall frequency of preclinical AD (of any stage) was 17.2% (95% CI: 12.0 - 23.0%) with a high statistical heterogeneity of I2 = 64%. In meta-regression, being the Japanese cohort was barely significantly associated with the lower frequency of preclinical AD (p = 0.048). ConclusionsOur study suggested that currently there is no robust evidence to support the lower frequency of preclinical AD in clinical study settings of Japan than that of Western countries.