Practice and drop-out effects during a 17-year longitudinal study of cognitive aging

Rabbitt, Patrick, Diggle, Peter, Holland, Fiona and McInnes, Lynn (2004) Practice and drop-out effects during a 17-year longitudinal study of cognitive aging. Journals of Gerontology, 59 (2). P84-P97. ISSN 1079-5014

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Abstract

Interpretations of longitudinal studies of cognitive aging are misleading unless effects of practice and selective drop-out are considered. A random effects model taking practice and drop-out into account analyzed data from four successive presentations of each of two intelligence tests, two vocabulary tests, and two verbal memory tests during a 17-year longitudinal study of 5,899 community residents whose ages ranged from 49 to 92 years. On intelligence tests, substantial practice effects counteracted true declines observed over 3 to 5 years of aging and remained significant even with intervals of 7 years between successive assessments. Adjustment for practice and drop-out revealed accelerating declines in fluid intelligence and cumulative learning, linear declines in verbal free recall, and no substantial change in vocabulary. Socioeconomic status and basal levels of general fluid ability did not affect rates of decline. After further adjustment for demographics, variability between individuals was seen to increase as the sample aged.

Item Type:	Article
Additional Information:	McInnes is fourth author, but is an equal status author. This work was funded by an ESRC grant awarded to McInnes as Investigator (1998-2003). She is panel manager for the North East Age research project, and the data were collected and analysed by her in Newcastle.
Subjects:	A900 Others in Medicine and Dentistry C800 Psychology
Department:	Faculties > Health and Life Sciences > Psychology
Depositing User:	EPrint Services
Date Deposited:	09 Dec 2008 12:52
Last Modified:	12 Oct 2019 16:27
URI:	http://nrl.northumbria.ac.uk/id/eprint/2650

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