title: Intraindividual variability across cognitive tasks as a potential marker for prodromal Alzheimer's disease.
abstract: Recent studies have shown that increased cognitive intraindividual variability (IIV) across accuracy scores from tests representing different cognitive domains (across-domain IIV) might indicate prodromal Alzheimer's disease (AD). Although IIV has been proposed to index cognitive control processes, IIV across accuracy scores from cognitive control tasks (within-domain IIV) has not been examined in healthy controls subjects (HCS), mild cognitive impairment (MCI), and AD patients in a single comparative study. This study examines the discriminative properties of within-domain IIV, and across-domain IIV in 149 HCS, 31 MCI, and 26 AD. Three tasks representing different cognitive domains were identified to calculate across-domain IIV. Three other tasks representing cognitive control were identified to calculate within-domain IIV. The intraindividual standard deviation was calculated across accuracy scores. To compare IIV between groups, ANCOVAs with the covariates age, gender, education, and mean performance were computed. IIV scores in general were higher in AD vs. HCS (p < 0.01). Only across-domain IIV was higher in AD vs. MCI (p = 0.001), and only within-domain IIV was higher in MCI vs. HCS (p = 0.05). Within-domain IIV may constitute a cognitive marker for the detection of prodromal AD at the MCI stage, whereas across-domain IIV may detect beginning AD at the MCI stage.
authors: Division of Psychiatry Research and Psychogeriatric Medicine, University of Zurich, Zurich Switzerland.
authors: Andrea M
authors: AM
authors: Kälin
authors: Department of Forensic Psychiatry, Psychiatric University Clinics, University of Basel, Basel Switzerland.
authors: Marlon
authors: M
authors: Pflüger
authors: Division of Psychiatry Research and Psychogeriatric Medicine, University of Zurich, Zurich Switzerland.
authors: Anton F
authors: AF
authors: Gietl
authors: Division of Psychiatry Research and Psychogeriatric Medicine, University of Zurich, Zurich Switzerland.
authors: Florian
authors: F
authors: Riese
authors: Division of Neuropsychology, Institute of Psychology, University of Zurich, Zurich Switzerland ; International Normal Aging and Plasticity Imaging Center, University of Zurich, Zurich Switzerland ; University Research Priority Program "Dynamics of healthy aging", University of Zurich, Zurich Switzerland.
authors: Lutz
authors: L
authors: Jäncke
authors: Division of Psychiatry Research and Psychogeriatric Medicine, University of Zurich, Zurich Switzerland.
authors: Roger M
authors: RM
authors: Nitsch
authors: Division of Psychiatry Research and Psychogeriatric Medicine, University of Zurich, Zurich Switzerland.
authors: Christoph
authors: C
authors: Hock
keywords: Alzheimer’s disease; cognitive control; cognitive variability; early diagnosis; mild cognitive impairment; neuropsychology