Lower practice effects as a marker of cognitive performance and dementia risk: A literature review.
BACKGROUND
Practice effects (PEs) are improvements in performance after repeated exposure to test materials, and typically viewed as a source of bias in repeated cognitive assessments. We aimed to determine whether characterizing PEs could also provide a useful marker of early cognitive decline.


METHODS
We conducted a systematic review of the literature, searching PsycInfo (Ebsco) and PubMed databases for articles studying PEs in aging and dementia populations. Articles published between 1920 and 2019 were included.


RESULT
We identified 259 articles, of which 27 studied PEs as markers of cognitive performance. These studies consistently showed that smaller, less-robust PEs were associated with current diagnostic status and/or future cognitive decline. In addition, lower PEs were associated with Alzheimer's disease risk factors and neurodegeneration biomarkers.


CONCLUSION
PEs provide a potentially useful marker of cognitive decline, and could prove valuable as part of a cost-effective strategy to select individuals who are at-risk for dementia for future interventions.