Objective
Older men on average have lower testosterone concentrations compared with younger men, and more age-related comorbidities. Whether lower testosterone concentrations contribute to biological ageing remains unclear. Shorter telomeres are a marker for advanced biological age. We tested the hypothesis that testosterone concentrations are associated with leucocyte telomere length (LTL), in middle to older aged men.
Design
Cross-sectional analysis of the UK Biobank study, involving community-dwelling men aged 40-69 years.
Methods
Serum testosterone and sex hormone-binding globulin (SHBG) were assayed. Free testosterone was calculated (cFT). Leucocyte telomere length (LTL) was measured using Polymerase Chain Reaction. Linear mixed models were fitted to LTLs.
Results
In 167,706 men, median age 58 years, standardised LTL was inversely associated with total testosterone after adjusting for sociodemographic, lifestyle and medical factors (P<0.001; effect size 0.09, 95% confidence interval [CI], 0.08-0.10 longer LTL for men with total testosterone at median of lowest quintile [Q1] vs highest [Q5]). This relationship was attenuated after additional adjustment for SHBG (P=0.003; effect size 0.03, CI=0.02-0.05). The association between cFT and LTL was similar in direction but lower in magnitude to that found with total testosterone. After adjusting for sociodemographic, lifestyle and medical factors, SHBG was inversely associated with LTL (P<0.001; effect size 0.12, 95% CI 0.10-0.13 longer LTL for SHBG at median Q1 vs Q5). These results were largely unchanged after additional adjustment for testosterone (P<0.001; effect size 0.10, CI=0.08-0.12).
Conclusions
Total testosterone and SHBG were independently and inversely associated with LTL. Men with higher testosterone or higher SHBG had shorter telomeres, which would be consistent with more advanced biological age. These findings argue against a role for testosterone to slow biological ageing in men.