# Weighting and standardization of frequencies to determine prevalence of AD imaging biomarkers

## Document Type

Article

## Abstract

© 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.

## Publication Date

1-1-2017

## Publication Title

Neurology

## ISSN

00283878

## Volume

89

## Issue

20

## First Page

2039

## Last Page

2048

## PubMed ID

29030451

## Digital Object Identifier (DOI)

10.1212/WNL.0000000000004652

## Recommended Citation

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*. 366.

https://scholar.barrowneuro.org/neurology/366