Background — Injury causes significant morbidity and mortality that is sometimes attributed to testosterone and violence. We hypothesized that prescribed testosterone might be associated with the subsequent risk of serious injury.
Methods — We conducted a self-matched individual-patient exposure-crossover analysis comparing injury risks before and after initiation of testosterone. We selected adults treated with testosterone in Ontario, Canada, from October 1, 2012 to October 1, 2017 (enrollment) and continued until October 1, 2018 (follow-up). The primary outcome was defined as an acute traumatic event that required emergency medical care.
Results — A total of 64,386 patients were treated with testosterone, of whom 89% were men with a median age of 52 years. We identified 34,439 serious injuries during the baseline interval before starting testosterone (584 per month) and 7,349 serious injuries during the subsequent interval after starting testosterone (565 per month). Rates of injuries were substantially above the population norm in both intervals with no significant increased risk after starting testosterone (relative risk = 1.00; 95% confidence interval: 0.96 to 1.04, P = 0.850). The unchanged risk extended to diverse patients, was observed for different formulations, and applied to all injury mechanisms. In contrast, testosterone treatment was associated with a 48% increased risk of a thromboembolic event (relative risk = 1.48; 95% confidence interval: 1.25 to 1.74, P < 0.001).
Conclusions — Testosterone treatment was associated with a substantial baseline risk of serious injury that did not increase further after starting therapy. Physicians prescribing testosterone could consider basic safety reminders to mitigate injury risks.