Matt McGue1, Kaare Christensen2,
In 1995 we initiated the Longitudinal Study of Aging Danish Twins by assessing the health, physical functioning, cognitive status and depression symptomatology of all living and willing Danish twins aged 75 years and older (N=2401 or 78% of the target population). In 1997, the survey was repeated on all twins aged 73 years and older (N=2172 or 79% of the target population). In both surveys, cognitive status was assessed using the Mini Mental State Examination (MMSE) and a battery of five brief cognitive tests. Analysis of the 1995 cognitive data revealed that approximately 50% of the variability in cognitive functioning and liability to cognitive impairment was associated with genetic factors, with the balance of variance being associated with nonshared environmental factors. For the 1595 twins who completed both the 1995 (at an average age of 80.9 years) and the 1997 (average age of 82.8 years) LSADT surveys, there were significant declines in average performance on all of the cognitive tests (standardized effect sizes ranged from .10 to .70), but significant stability of individual differences (retest correlations ranged from .36 to .65). Findings from a joint analysis of the cognitive data from the two surveys will be presented and discussed in the terms of whether the heritability of cognitive functioning appears to increase, decrease or remain stable in late-life.
Address: 75 East River Rd., Minneapolis, MN., 55455, (612)-625-8305, (612)-626-2079(FAX), mmcgue@tfs.psych.umn.edu
1Department of Psychology, University of Minnesota, Minneapolis, MN 55455. 2Odense University Medical School, Odense Denmark. 3Supported by NIH grant P01-AG08761