Cross‐sectional comparison of the role of tau burden among Down Syndrome Alzheimer disease and autosomal‐dominant Alzheimer disease
Authors: Wisch Julie K. , Gordon Brian A. , Boerwinkle Anna H. , Flores Shaney , McKay Nicole S. , Henson Rachel L. , Thippabhotla Sharmila , Kennedy James Tyler , Butt Omar Hameed , Chen Charles D. , Handen Benjamin L. , Christian Bradley T. , Head Elizabeth , Mapstone Mark , Tudorascu Dana , Zammit Matthew D , Cohen Annie , Johnson Sterling C , Fagan Anne M. , Klunk William E , Rafii Michael S , O'Bryant Sid E. , Price Julie C , Schupf Nicole , Laymon Charles M , Yassa Michael A. , Keator David B. , Krinsky‐McHale Sharon J , Lai Florence , Rosas H. Diana , Hartley Sigan , Zaman Shahid , Lott Ira T , Silverman Wayne , Lao Patrick J. , Brickman Adam M. , Lee Joseph H. , Allegri Ricardo Francisco , Berman Sarah , Chhatwal Jasmeer P. , Chui Helena C , Cruchaga Carlos , Farlow Martin R. , Fox Nick C , Goate Alison , Day Gregory S. , Graff‐Radford Neill R , Jucker Mathias , Lee Jae‐Hong , Levin Johannes , Martins Ralph N , Mori Hiroshi , Perrin Richard J. , Salloway Stephen , Sanchez‐Valle Raquel , Schofield Peter W. , Xiong Chengjie , Schindler Suzanne E. , Morris John C , Karch Celeste M. , Hassenstab Jason J. , Benzinger Tammie L.S. , McDade Eric , Bateman Randall J. , Ances Beau ,   and the Alzheimer’s Biomarker Consortium‐Down Syndrome and the Dominantly Inherited Alzheimer Network
Published: December 2023

Background

Adults with Down Syndrome (DS) develop Alzheimer disease (AD)‐like pathology and dementia as they age. This is attributed to triplication of the amyloid precursor protein gene. Recent work demonstrated that amyloid is elevated in DS and accumulates in a similar topography to autosomal dominant AD (ADAD). Tau accumulation is the second hallmark of AD and may be measured using tau positron emission tomography (PET) imaging. The pattern of tau accumulation remains unknown in DS.

Method

In a cross‐sectional analysis we evaluated amyloid and tau positron emission tomography (PET) in 124 participants with DS (109 cognitively stable, 8 symptomatic, 7 no consensus), 29 ADAD mutation carriers (26 asymptomatic, 3 symptomatic), and 201 cognitively normal non‐mutation carriers (CN). Regional cortical standard uptake value ratios (SUVR) for tau imaging were obtained and compared by cognitive status. Similarly, regional cortical amyloid SUVR were obtained and converted to centiloids. We then compared the magnitude of tau burden as well as spatial spread of tau across groups relative to amyloid burden.

Result

Compared to CN, tau PET binding was elevated in participants with (µDS = 2.12 ± 0.22 SUVR, µADAD = 2.52 ± 0.37 SUVR) and without (µDS = 1.24 ± 0.15 SUVR, µADAD = 1.16 ± 0.19 SUVR) cognitive changes. For both groups, tau increased with increasing amyloid (centiloids). In some regions, DS had greater tau burden for a given amyloid level (centiloids) (Figure 1). There was increased spatial distribution of tau throughout the brain for participants with DS compared to CN. In contrast, tau burden was more focal in participants with ADAD with tau primarily elevated in posterior regions (Figure 2).

Conclusion

While tau burden was higher with symptomatic disease for both groups, significant differences existed in the overall amount and spatial spread. Tau spread was greatest in participants with DS and more diffuse compared to ADAD. These results indicate a substantial tau burden is present in DS, and suggest not only anti‐amyloid but also tau‐reducing agents should be considered for treating cognitive decline in adults with DS.