title: Intraindividual variability is a fundamental phenomenon of aging: evidence from an 8-year longitudinal study across young, middle, and older adulthood.
abstract: Moment-to-moment intraindividual variability (IIV) in cognitive speed is a sensitive behavioral indicator of the integrity of the aging brain and brain damage, but little information is known about how IIV changes from being relatively low in young adulthood to substantially higher in older adulthood. We evaluated possible age group, sex, and task differences in IIV across adulthood using a large, neurologically normal, population-based sample evaluated thrice over 8 years. Multilevel modeling controlling for education, diabetes, hypertension, and anxiety and depressive symptoms showed expected age group differences in baseline IIV across the adult lifespan. Increase in IIV was not found until older adulthood on simple tasks but was apparent even in the 40s on a more complex task. Females were more variable than males but only at baseline. IIV in cognitive speed is a fundamental behavioral characteristic associated with growing older, even among healthy adults.
authors.affiliation: Department of Human Development and Family Studies.
authors.forename: Allison A M
authors.initials: AA
authors.lastname: Bielak
authors.affiliation: Centre for Research on Ageing, Health and Wellbeing, The Australian National University.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Cherbuin
authors.affiliation: Institute of Psychological Sciences, Faculty of Medicine and Health, University of Leeds.
authors.forename: David
authors.initials: D
authors.lastname: Bunce
authors.affiliation: Centre for Research on Ageing, Health and Wellbeing, The Australian National University.
authors.forename: Kaarin J
authors.initials: KJ
authors.lastname: Anstey
mesh_terms: D000328:Adult; D000375:Aging / Q000523:psychology*; D002755:Choice Behavior / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D008875:Middle Aged; D011930:Reaction Time / Q000502:physiology; D012044:Regression Analysis; D012727:Sex Characteristics; D055815:Young Adult