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How heritable is individual susceptibility to death? The results of an analysis of survival data on Danish, Swedish and Finnish twins

Published online by Cambridge University Press:  21 February 2012

Ivan A Iachine*
Affiliation:
Department of Statistics and Demography, Odense University, Denmark. [email protected]
Niels V Holm
Affiliation:
Institute of Community Health, Odense University, Denmark.
Jennifer R Harris
Affiliation:
Section for Epidemiology, National Institute of Public Health, Oslo, Norway; Division of Genetic Epidemiology, Institute of Environmental Medicine, The Karolinska Institute, Stockholm, Sweden.
Alexander Z Begun
Affiliation:
Max Planck Institute for Demographic Research, Rostock, Germany.
Maria K Iachina
Affiliation:
Aging Research Unit, Odense University, Denmark.
Markku Laitinen
Affiliation:
Department of Biology, University of Turku, Finland.
Jaakko Kaprio
Affiliation:
Department of Public Health, University of Helsinki, Finland.
Anatoli I Yashin
Affiliation:
Max Planck Institute for Demographic Research, Rostock, Germany; Duke University Center for Demographic Studies, Durham, North Carolina, USA.
*
*Correspondence: IA Iachine, Department of Statistics and Demography, Odense University, Hollufgaard, Hestehaven 201, DK-5220 Odense SO, Denmark. Phone: + 45 6557 3604; Fax: + 45 6595 7766

Abstract

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Molecular epidemiological studies confirm a substantial contribution of individual genes to variability in susceptibility to disease and death for humans. To evaluate the contribution of all genes to susceptibility and to estimate individual survival characteristics, survival data on related individuals (eg twins or other relatives) are needed. Correlated gamma-frailty models of bivariate survival are used in a joint analysis of survival data on more than 31 000 pairs of Danish, Swedish and Finnish male and female twins using the maximum likelihood method. Additive decomposition of frailty into genetic and environmental components is used to estimate heritability in frailty. The estimate of the standard deviation of frailty from the pooled data is about 1.5. The hypothesis that variance in frailty and correlations of frailty for twins are similar in the data from all three countries is accepted. The estimate of narrow-sense heritability in frailty is about 0.5. The age trajectories of individual hazards are evaluated for all three populations of twins and both sexes. The results of our analysis confirm the presence of genetic infiuences on individual frailty and longevity. They also suggest that the mechanism of these genetic infiuences may be similar for the three Scandinavian countries. Furthermore, results indicate that the increase in individual hazard with age is more rapid than predicted by traditional demographic life tables.

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Articles
Copyright
Copyright © Cambridge University Press 1998