Cognitive change in aging: A life span perspective of gender and individual differences in APOE genotype

Abstract: Degree of licentiate in Psychology Abstract Praetorius, M. (2011). Cognitive change in aging: A life span p erspective of gender and individual differences in APOE genotype. Department of Psychology, University of Gothenburg, Sweden The world population is aging and which unfortunately produces greater challenges because of the increasing risk with age for cognitive ilI-health. In that sense, research on potential risk factors from a life span perspective is of importance. The aim of the thesis was to investigate how two congenitai factors Apolipoprotein E and gender, influence mortality related cognitive performance in late life. The genetic predisposition remains throughout the life span although influences on functioning and cognitive performance can differ over time. The effect of gender is more clearly influenced by the social environment through life style and cohort differences. In the two studies, we used the same statistical analyses, mixed level modelling, to analyze longitudinal data and both also took individual differences in mortality/survival into account for a better understanding of cognitive performance in late life. The aim of study I was to examine the assumed negative association between the APOE e4 allele and cognitive change in old age and we investigate the potential contribution of incident dementia for this association. The sample consisted of 366 non-demented individuals and 116 incident dementia cases, with confirmed death dates, aged 80 years and older, bom 1893-1913 and drawn from the OCTO-twin study. We found that there was a negative effect of the APOE e4 allele on cognitive performance in late life and that the association is moderated by incident dementia. The aim of study II was to examine gender differences in level and change in cognitive performance in oldest old in the context of time to death. Previous studies have found that gender differences in late life are stable, i.e. there is no change over the life-cycle. None of these studies, however, have taken gender differences in mortality and survival into account for these differences. 568 individuals with confirmed death dates aged 80 years and older, bom 1893-1913 was drawn from the OCTO-twin study. We used two different time metrics for analyzing gender differences. A linear chronological age metric and a linear time to death metric that was based on differences in mortality was applied. When we used the linear chronological age model we found gender differences in level of cognitive performance but not in change. When we employed the linear time to death mode! we found gen der differences in level of cognitive performance and also in change. Our results reflect that there are gender differences in level of cognitive performance and change in late life that is influenced by a female advantage in longevity. In sum, this thesis indicates that there is a relationship between cognitive performance and differences in mortality and survival in late life that is associated with differences 'given from birth', genes (APOE) and gender. The thesis also demonstrates the importance of investigating differences in the APOE genotype and gender differences for cognitive leve! of functioning and change in the context of time to death. Keywords: cognitive performance, late life, APOE, gender, time to death ISSN 1101-718X ISRN GUIPSYKlA VH--257--SE Marcus Praetorius, Department of Psychology, University of Gothenburg, Box 500, 504 30, Gothenburg, Sweden. Phone: +46317861646, E-mail: [email protected]