Nonlinear association between vitamin D levels and response to tadalafil 5 mg daily treatment in erectile dysfunction...

Erectile dysfunction (ED) is a common male sexual disorder. Vitamin D (VD) deficiency is frequent in ED patients and has been associated with greater disease severity, but its role in predicting treatment response remains unclear. In this prospective cohort study, 202 ED patients were initially enrolled, and after excluding 30 ineligible cases, 172 were included in the final analysis at Chengdu University of TCM Affiliated Hospital (September 2023-August 2024). ED severity was evaluated using the International Index of Erectile Function-5 (IIEF-5) during a 1-month follow-up, with 152 patients (88.4%) reporting symptomatic improvement after daily tadalafil 5 mg treatment. Patients with VD ≥ 20 ng/mL showed faster responses. Multivariate Cox regression demonstrated a significant positive association between baseline VD levels and treatment outcomes (adjusted hazard ratio = 1.60 per 1 ng/mL increase; 95% confidence interval: 1.31-1.95). Restricted Cubic Spline analysis revealed a nonlinear relationship, with the strongest effect observed at VD ≤ 19.6 ng/mL, representing a data-driven inflection point. Interaction analyses further confirmed consistent benefits across all age groups. These findings indicate that baseline VD is an independent prognostic factor for tadalafil efficacy in ED, highlighting its potential clinical utility for risk stratification and individualized treatment decisions in ED.