The prevalence of cerebral amyloid pathology, as determined by positron emission tomography or cerebrospinal fluid, among subjects without dementia, is associated with age, APOE genotype, and presence of cognitive impairment, according to a meta-analysis including 2,914 subjects with normal cognition, 671 with subjective cognitive impairment (SCI), and 3,972 with mild cognitive impairment (MCI).
Among the 3 groups, the prevalence of amyloid pathology increased from age 50 to age 90 as follows:
| Age 50 | Age 90 | |
| normal | 10% | 44% |
| SCI | 12% | 34% |
| MCI | 27% | 71% |
When stratified by APOE status, the age at which 15% of the participants with normal cognition were amyloid positive was:
• APOE e4e4 carriers: 40 years
• APOE e2e4 carriers: 50 years
• APOE e3e4 carriers: 55 years
• APOE e3e3 carriers: 65 years
• APOE e2e3 carriers: 95 years
“These finding suggest a 20- to 30-year interval between first development of amyloid positivity and onset of dementia,” the study authors wrote.
Citation: Jansen WJ, Ossenkoppele R, Knol DL, et al; Amyloid Biomarker Study Group. Prevalence of cerebral amyloid pathology in persons without dementia: a meta-analysis. JAMA. 2015;313(19):1924-1938. doi: 10.1001/jama.2015.4668.