Ouroboros comments on recent research indicating that infection shortens telomeres in immune cells: "Chronic stress has been associated with decreased telomere length in lymphocytes. The association is robust and has been observed in multiple studies ... The question still remains, however, whether the relationship is correlative or causative. Do stress and other lifestyle factors somehow cause shortened telomeres, or are the two phenomena otherwise-unrelated indications of some common underlying cause? ... Chronic infection requires increased production of lymphocytes, which overworks the stem cell compartment from which these cells are derived; increased cell divisions leads to decreased telomere length - a perfectly satisfactory explanation for the observation. If that is true, then chronic infection in the absence of lifestyle risk factors should cause telomere shortening on its own (let's stipulate for the moment that stress increases susceptibility to disease, an idea supported by my own anecdotal experience of college finals). Ilmonen et al. have demonstrated that this is indeed the case, at least in [mice]."