A meta-analysis of 55 studies found that cerebral amyloid pathology is prevalent in individuals without dementia, with prevalence increasing with age. Among those with normal cognition, the prevalence of amyloid pathology ranged from 10% at age 50 to 44% at age 90. For those with subjective cognitive impairment (SCI), it ranged from 12% to 43%, and for those with mild cognitive impairment (MCI), from 27% to 71%. APOE ε4 carriers had significantly higher prevalence than noncarriers. Amyloid positivity was more common in highly educated individuals but not associated with sex or biomarker modality. The study suggests a 20- to 30-year interval between the first development of amyloid positivity and the onset of dementia. The findings indicate that MCI is a risk state for Alzheimer's disease, and that amyloid positivity is associated with APOE genotype and cognitive status. The study also found that amyloid positivity was not significantly different between men and women, and that PET and CSF biomarkers showed similar prevalence estimates. The study highlights the importance of APOE genotype in predicting amyloid positivity and suggests that amyloid positivity should be viewed as a risk state rather than an inevitable precursor to dementia. The study's findings have implications for the design of prevention studies and the understanding of the development of Alzheimer's disease.A meta-analysis of 55 studies found that cerebral amyloid pathology is prevalent in individuals without dementia, with prevalence increasing with age. Among those with normal cognition, the prevalence of amyloid pathology ranged from 10% at age 50 to 44% at age 90. For those with subjective cognitive impairment (SCI), it ranged from 12% to 43%, and for those with mild cognitive impairment (MCI), from 27% to 71%. APOE ε4 carriers had significantly higher prevalence than noncarriers. Amyloid positivity was more common in highly educated individuals but not associated with sex or biomarker modality. The study suggests a 20- to 30-year interval between the first development of amyloid positivity and the onset of dementia. The findings indicate that MCI is a risk state for Alzheimer's disease, and that amyloid positivity is associated with APOE genotype and cognitive status. The study also found that amyloid positivity was not significantly different between men and women, and that PET and CSF biomarkers showed similar prevalence estimates. The study highlights the importance of APOE genotype in predicting amyloid positivity and suggests that amyloid positivity should be viewed as a risk state rather than an inevitable precursor to dementia. The study's findings have implications for the design of prevention studies and the understanding of the development of Alzheimer's disease.