THE HERITABILITY OF HUMAN LONGEVITY - A POPULATION-BASED STUDY OF 2872 DANISH TWIN PAIRS BORN 1870-1900

The aim of this study was to explore, in a large and non-censored twin cohort, the nature (i.e., additive versus non-additive) and magnitude (i.e., heritability) of genetic influences on inter-individual differ ences in human longevity. The sample comprised all identified and trac ed non-emigrant like-sex twin pairs born in Denmark during the period 1870-1900 with a zygosity diagnosis and both members of the pairs surv iving the age of 15 years. A total of 2872 pairs were included. Age at death was obtained from the Danish Central Person Register, the Danis h Cause-of-Death Register and various other registers. The sample was almost non-censored on the date of the last follow-up (May 1, 1994), a ll but 0.6% had died, leaving a total of 2872 pairs for analysis. Prop ortions of variance attributable to genetic and environmental factors were assessed from variance-covariance matrices using the structural e quation model approach. The most parsimonious explanation of the data was provided by a model that included genetic dominance (non-additive genetic effects caused by interaction within gene loci) and non-shared environmental factors (environmental factors that are individual-spec ific and not shared in a family). The heritability of longevity was es timated to be 0.26 for males and 0.23 for females. The small sex-diffe rence was caused by a greater impact of non-shared environmental facto rs in the females. Heritability was found to be constant over the thre e 10-year birth cohorts included. Thus, longevity seems to be only mod erately heritable. The nature of genetic influences on longevity is pr obably non-additive and environmental influences non-shared. There is no evidence for an impact of shared (family) environment.