Gender and telomere length: Systematic review and meta-analysis

• Systematic review examining the association between gender and telomere length
• Calculated summary estimates using random-effects meta-analyses.
• Heterogeneity between studies was investigated using meta-regression.
• On average females had longer telomeres than males.
• Only Southern blot showed a significant gender difference in telomere length.

BackgroundIt is widely believed that females have longer telomeres than males, although results from studies have been contradictory.MethodsWe 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 (by November 2009) 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.ResultsMeta-analyses from 36 cohorts (36,230 participants) showed that on average females had longer telomeres than males (standardised difference in telomere length between females and males 0.090, 95% CI 0.015, 0.166; age-adjusted). There was little evidence that these associations varied by age group (p = 1.00) or cell type (p = 0.29). However, the size of this difference did vary by measurement methods, with only Southern blot but neither real-time PCR nor Flow-FISH showing a significant difference. This difference was not associated with random measurement error.ConclusionsTelomere length is longer in females than males, although this difference was not universally found in studies that did not use Southern blot methods. Further research on explanations for the methodological differences is required.