title: Multivariate modeling of age and retest in longitudinal studies of cognitive abilities.
abstract: Longitudinal multivariate mixed models were used to examine the correlates of change between memory and processing speed and the contribution of age and retest to such change correlates. Various age- and occasion-mixed models were fitted to 2 longitudinal data sets of adult individuals (N>1,200). For both data sets, the results indicated that the correlation between the age slopes of memory and processing speed decreased when retest effects were included in the model. If retest effects existed in the data but were not modeled, the correlation between the age slopes was positively biased. The authors suggest that although the changes in memory and processing speed may be correlated over time, age alone does not capture such a covariation.
authors.affiliation: Department of Psychology, University of California, Davis, CA 95616-8686, USA. eferrer@ucdavis.edu
authors.forename: Emilio
authors.initials: E
authors.lastname: Ferrer
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Salthouse
authors.forename: John J
authors.initials: JJ
authors.lastname: McArdle
authors.forename: Walter F
authors.initials: WF
authors.lastname: Stewart
authors.forename: Brian S
authors.initials: BS
authors.lastname: Schwartz
mesh_terms: D000367:Age Factors; D000368:Aged; D003072:Cognition Disorders / Q000175:diagnosis* / Q000523:psychology; D006801:Humans; D007854:Lead; D020265:Lead Poisoning, Nervous System, Adult / Q000175:diagnosis* / Q000523:psychology; D008137:Longitudinal Studies; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000523:psychology; D008875:Middle Aged; D015233:Models, Statistical; D015999:Multivariate Analysis; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D011214:Practice, Psychological; D011446:Prospective Studies; D011594:Psychometrics / Q000706:statistics & numerical data*; D011930:Reaction Time; D012016:Reference Values; D015203:Reproducibility of Results; D013223:Statistics as Topic
chemical_list: D007854:Lead