To evaluate the association between long-term finasteride use and incident benign prostatic hyperplasia (BPH) and prostate cancer (PCa) diagnosis. Low-dose finasteride (1 mg) is widely prescribed for androgenic alopecia, often via telemedicine, resulting in prolonged use in men without baseline prostatic disease. While higher-dose finasteride is studied for BPH and PCa prevention, urologic outcomes of chronic low-dose use remain unclear.

In this retrospective cohort study using the TriNetX Research Network, adult men with androgenic or nonscarring alopecia and no prior BPH or PCa were included. Exposure cohorts were defined by continuous finasteride 1 mg use for ≥3 or ≥5 years and compared to alopecia controls without finasteride. Cohorts were matched 1:1 via propensity scores for demographics, comorbidities, labs, medications, and healthcare utilization. Time-to-event analyses used Kaplan-Meier and Cox models, with hazard ratios (HRs) as the primary measure.

After matching, 6741 patients per group comprised the 3-year cohort and 4534 per group the 5-year cohort. At three years, finasteride was associated with lower BPH (HR 0.64, 95% CI 0.55–0.75) and PCa diagnosis (HR 0.49, 95% CI 0.33–0.74). At five years, finasteride was associated with lower BPH (HR 0.52, 95% CI 0.43–0.63) and PCa diagnosis (HR 0.47, 95% CI 0.28–0.79). Patterns were consistent for symptomatic and asymptomatic BPH. Absolute PCa diagnosis rates remained low.

In men treated for alopecia, long-term low-dose finasteride was associated with reduced incident BPH and PCa diagnosis. Prospective studies are needed to clarify mechanisms and long-term clinical implications.