Association of Testosterone and Sex Hormone-Binding Globulin With All-Cause and Cardiovascular Disease Mortality in Older Chinese Men.

Background: The associations of high and low testosterone with all-cause and cardiovascular disease (CVD) mortality risk in men are conflicting. Our objective was to examine associations of total testosterone, free testosterone, bioavailable testosterone, and sex hormone-binding globulin (SHBG) with all-cause and CVD mortality in older Chinese men.

Methods: Total testosterone and SHBG were assayed, and free testosterone and bioavailable testosterone were calculated using Vermeulen formula. Cox proportional hazards regression was used to assess the associations with risks of all-cause and CVD mortality, giving hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: Of 3 948 men aged 50+ years, 949 deaths (312 CVD) occurred during an average 10.5-year follow-up. After multivariable adjustments, the highest, versus the third, quartile of total testosterone and free testosterone were associated with higher all-cause mortality risk (1.17 [0.97-1.41] and 1.45 [1.20-1.74], respectively), whereas free testosterone was associated with higher CVD mortality risk (1.88 [1.33-2.66]). Similar positive associations were found for bioavailable testosterone and all-cause mortality risk (1.27 [1.05-1.54]). Lower SHBG (quartile 1 vs quartile 3) was associated with higher all-cause and CVD mortality risk (1.25 [1.04-1.52] and 1.28 [1.08-1.52], respectively). Consistent associations were observed in relatively healthy men and men excluded death during the first year.

Conclusions: Higher total testosterone, free testosterone, and bioavailable testosterone were associated with higher all-cause mortality in older men, higher free testosterone was associated with higher CVD mortality whilst lower SHBG was associated with higher all-cause and CVD mortality. Clarification and confirmation of causality require further mechanistic studies.