Weighting and standardization of frequencies to determine prevalence of AD imaging biomarkers
© 2017 American Academy of Neurology. Objective: To estimate the prevalence of elevated brain amyloid and reduced cortical thickness (as a marker for neurodegeneration) in a defined population. Methods: Mayo Clinic Study of Aging participants underwent MRI to assess a composite Alzheimer disease (AD) signature cortical thickness measure and PET to assess brain amyloid accumulation. Participants were characterized as having elevated amyloid (A+/A-), reduced cortical thickness (N+/N-), and A+N+, A+N-, A-N+, or A-N-. The prevalence of AD biomarkers was derived by adjusting for nonparticipation and standardizing to the Olmsted County, Minnesota, population. Results: Among 1,646 participants without dementia (mean age 70.8 years; 53.2% men), the prevalence (95% confidence interval) of amyloidosis was 21.1% (19.1%-23.2%): women, 24.3%; men, 17.5%. The prevalence of reduced cortical thickness was 28.9% (26.4%-31.5%): women, 27.9%; men, 30.2%. The prevalence estimates of biomarker categories were as follows: A-N-: 61.4%; A+N-: 9.7%; A-N+: 17.4%; and A+N+: 11.5%, and varied by sex and by APOE ϵ4 carrier status. In men, prevalence estimates were as follows: A-N-: 62.6%; A+N-: 7.3%; A-N+: 19.9%; and A+N+: 10.2%. In women, prevalence estimates were as follows: A-N-: 60.4%; A+N-: 11.7%; A-N+: 15.3%; and A+N+: 12.6%. In ϵ4 carriers, prevalence estimates were as follows: A-N-: 54.6%; A+N-: 16.6%; A-N+: 12.4%; and A+N+: 16.4%. In non-ϵ4 carriers, prevalence estimates were as follows: A-N-: 63.3%; A+N-: 6.9%; A-N+: 19.9%; and A+N+: 10.0%. Conclusions: These prevalence estimates are important for understanding age-related trends in amyloid positivity and AD signature cortical thickness in the population, and for potentially projecting the future burden of biomarkers in elderly persons.
Digital Object Identifier (DOI)
Roberts, Rosebud O.; Knopman, David S.; Syrjanen, Jeremy A.; Aakre, Jeremiah A.; Vassilaki, Maria; Kremers, Walter K.; Mielke, Michelle M.; Machulda, Mary M.; Graff-Radford, Jonathan; Geda, Yonas E.; Vemuri, Prashanthi; Lowe, Val; Jack, Clifford R.; and Petersen, Ronald C., "Weighting and standardization of frequencies to determine prevalence of AD imaging biomarkers" (2017). Neurology Articles. 366.