Telomeres are essential in maintaining chromosome integrity and in controlling cellular replication. Attrition of telomere length in peripheral blood mononuclear cells (PBMCs) with age is well documented from cross-sectional studies. But the actual in vivo changes in telomere lengths and its relationship with the contributing factors within individuals with age have not been fully addressed. Here, we report a longitudinal analysis of telomere length in PBMCs, lymphocytes and monocytes of two hundred and sixteen human subjects aged from 20s to 90s assessed at zero, five- and twelve- year follow-up. For the 5- and 12-year follow-up, telomere length in PBMCs decreased in 34% and 46%, exhibited no detectable change in 56% and 47%, and increased in 10% and 7% of the subjects, respectively. The rate of telomere change was distinct for T-, B-cells and monocytes for any given subject. Telomerase activity declined with age in resting T- and B cells and activated T cells. Finally, a significant portion of telomere attrition in T cells with age was explained by a decline in telomerase activity, decreased naive cells and the change in physiological conditions such as elevated blood glucose and IL-6 levels.These findings show that changes in telomere length of PBMCs with age in vivo occur at different rates in different individuals and cell types, and reveal that changes in telomere length in T cells with age is influenced by telomerase activity, naïve T cell percentage and changes in health conditions.
PMID: 25317735

Age-associated telomere attrition of lymphocytes in vivo is co-ordinated with changes in telomerase activity, composition of lymphocyte subsets and health conditions.