Previous research including a 2003 Lancet paper (Lancet 2003; 361: 393-95) has shown that the relative length of the ends of chromosomes (telomeres) is associated with age-related illness and mortality (shorter telomeres being associated with increased age-related illness and earlier death). Furthermore, on the basis of studies among twins, telomere length seems to be inheritable, but little is known about its mode of inheritance.
Jan A Staessen from the University of Leuven, Belgium, and colleagues measured telomere length in white-blood-cell DNA taken from people already enrolled in the family-based cohort of the Flemish Study on Environment, Genes, and Health Outcomes. The investigators found that telomere length was similar between fathers and daughters, mothers and sons, mothers and daughters, and among siblings, but not among fathers and sons or between spouses. In other words, the inheritance of a parental X chromosome (from mothers for sons, and from both parents for daughters) was strongly correlated with similar telomere length between parents and children.
Dr Staessen comments: "X-linked inheritance of telomere length is the most probable explanation for our findings. Pending confirmation, our observations suggest that the process of ageing might be an X-linked trait."