Here we have shown that the frequency of subjects with detectable clonal mosaicism for large chromosomal anomalies in peripheral blood is low (<0.5%) from birth until 50 years of age, after which it rises rapidly. This relationship between mosaicism and age is very robust to both study and subject characteristics. Among the covariates sex, ethnicity, smoking and disease status (exclusive of hematological cancer), none had a significant effect on mosaic status. The age effect in GENEVA subjects is consistent with a recent study showing that acquired differences in structural chromosome variants between members of monozygotic twin pairs (including clonal mosaic anomalies) are observed in pairs >55 years of age but not in younger pairs29. Nevertheless, longitudinal studies are required to rule out the possibility that a trend in environmental exposures across birth cohorts may contribute to the increase in mosaicism with age.
