Women tend to live longer than men for reasons that remain much debated, an example of the way in which identifying cause and effect for natural variations in longevity can be very challenging. Telomeres, the caps of repeating DNA sequences at the end of chromosomes, tend to become shorter on average with age and illness. Some forms of telomere length measurement in some tissues may be useful as a biomarker of aging, but so far this hasn't proven to be straightforward. Given these two line items we might expect to find that women have longer telomeres than men, once the details are sorted out:
It is widely believed that females have longer telomeres than males, although results from studies have been contradictory. We carried out a systematic review and meta-analyses to test the hypothesis that in humans, females have longer telomeres than males and that this association becomes stronger with increasing age. Searches were conducted in EMBASE and MEDLINE and additional datasets were obtained from study investigators. Eligible observational studies measured telomeres for both females and males of any age, had a minimum sample size of 100 and included participants not part of a diseased group. We calculated summary estimates using random-effects meta-analyses. Heterogeneity between studies was investigated using sub-group analysis and meta-regression.
Meta-analyses from 36 cohorts (36,230 participants) showed that on average females had longer telomeres than males. There was little evidence that these associations varied by age group or cell type. However, the size of this difference did vary by measurement methods, with only Southern blot but neither real-time PCR nor FlowFISH showing a significant difference. This difference was not associated with random measurement error. Further research on explanations for the methodological differences is required.