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Sex Differences After All Those Years? Heritability of Cognitive Abilities in Old Age

¹ School of Health Sciences, Institute of Gerontology, Jönköping, Sweden.
² Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
³ Department of Psychology, University of Southern California, Los Angeles.
⁴ Department of Public Health, University of Helsinki, Finland.
⁵ Department of Psychology, University of Göteborg, Sweden.
⁶ Department of Biobehavioral Health and Center for Developmental and Health Genetics, The Pennsylvania State University, University Park.

Address correspondence to Sanna Read, Institute of Gerontology, School of Health Sciences, PO Box 1026, 551 11 Jönköping, Sweden. E-mail: sata{at}hhj.hj.se

We investigated sex differences in genetic and environmental effects on cognitive abilities among older adult twins. We drew participants from the Swedish Twin Registry; our sample included 647 twin pairs. Our cognitive measures included Synonyms, Block Design, Digit Span, Thurstone's Picture Memory, Symbol Digit, and general cognitive ability tests. Higher age was related to lower performance in all cognitive measures, except synonyms. For digit span forward, symbol digit, and general cognitive ability tasks, there was a Sex x Age interaction, with greater deficits in the performance of women compared with those of men at higher ages. We found no sex-specific genetic influences. In other words, the same genetic effects were operating for men and women. Furthermore, the magnitude of genetic effect was similar for men and women.