The discovery of minimally invasive and cost-effective blood-based biomarkers for dementia has the potential to transform clinical research and practice by permitting widespread low-cost screening, risk stratification, and efficient identification of persons with the greatest dementia risk for inclusion in dementia prevention trials. Single-molecule array technology permits the detection of total tau (t-tau) from plasma with a greater than 1000-fold improvement in sensitivity over conventional enzyme-linked immunosorbent assay (ELISA).
1,2 Plasma t-tau level measured with this technology is greater in persons with Alzheimer disease (AD) dementia or mild cognitive impairment (MCI) compared with control participants.
3-5 However, the usefulness of plasma t-tau as a diagnostic biomarker is limited by the large overlap in values observed between diagnostic groups, which may signal a lack of specificity for AD. The latest National Institute on Aging–Alzheimer Association Research Framework (NIA-AA) describes t-tau as a biomarker of neuronal injury rather than of neurofibrillary tangle burden, noting that an elevated t-tau level reflects neuronal injury from various causes.
6 Nevertheless, plasma t-tau shows early promise as a predictive biomarker for dementia with 2 longitudinal studies demonstrating that plasma t-tau is associated with endophenotypes of dementia, including cognitive decline.
7,8 However, evidence from representative community-based studies is limited, and studies to date have not been powered to examine the association with risk for dementia. Further studies are required to evaluate plasma t-tau as a predictive biomarker for incident dementia, permitting risk stratification in the setting where blood-based biomarkers would be most useful—in the general community and the age groups of relevance to early dementia prevention trials. Accordingly, we examined the association of plasma t-tau level as a predictive biomarker for dementia of any cause (all dementia) and incident dementia of the Alzheimer type (AD dementia) in the large community-based Framingham Heart Study (FHS), with replication performed in an independent multicenter cohort from France. We also examined endophenotypes associated with dementia, including cognitive function, hippocampal volume, and tau neurofibrillary tangle burden.