Absence of Practice Effects in Preclinical Alzheimer's Disease
Objective: To describe how practice effects influence cognitive trajectories and determine if a reduction in practice effects is a potential marker of Stage-III preclinical Alzheimer's disease (AD). Method: Participants included 263 older adults who were cognitively normal at baseline (i.e., ha...
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Veröffentlicht in: | Neuropsychology 2015-11, Vol.29 (6), p.940-948 |
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Zusammenfassung: | Objective: To describe how practice effects influence cognitive trajectories and determine if a reduction in practice effects is a potential marker of Stage-III preclinical Alzheimer's disease (AD). Method: Participants included 263 older adults who were cognitively normal at baseline (i.e., had a Clinical Dementia Rating [CDR] of 0; Morris, 1993) and returned for an average of 9.5 annual visits. Participants completed standard tests of episodic memory, visuospatial ability, semantic memory, and executive function. Progressors (n = 66) converted to CDR > 0 with a diagnosis of symptomatic AD after a minimum of 3 visits and stable participants (n = 197) never progressed to CDR > 0. Practice effects, defined as the slope of performance across Visits 1-3, were compared between groups and used within subjects to predict risk of conversion. Change-point models that accounted for retest were contrasted with linear models that ignored retest. Results: The stable group showed practice effects on episodic-memory measures (β = 0.14, SE = .02, p < .0001) but the progressor group did not (β = 0.03, SE = .03, p = .343). Across all participants, practice effects on episodic-memory tests were associated with a decreased risk of progression to AD as indicated by the subdistribution hazards model (SHR; Fine & Gray, 1999); SHR = .110, 95% CI [.032, .384], p = .001). Finally, use of change-point models dramatically altered rate-of-change estimates compared with models that ignored practice. Conclusion: Our results indicate that preclinical AD is marked by a reduction in practice effects in episodic memory and that the magnitude of gain from retesting is inversely related to progression risk. Assessment of practice effects may be a face-valid indicator of Stage-III preclinical AD. |
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ISSN: | 0894-4105 1931-1559 |
DOI: | 10.1037/neu0000208 |