BACKGROUND: Recent studies showed that the non-adherence to the pharmacological therapy of patients affected by BPH-associated LUTS increased the risk of clinical progression of BPH. We examined the patients adherence to pharmacological therapy and its clinical consequences in men with BPH-associated LUTS looking at the differences between drug classes comparing mono vs combination therapy.METHODS: A retrospective, population-based cohort study, using prescription administrative database and hospital discharge codes from a total of 1.5 million Italian men. Patients ≥ 40 years, administered alpha-blockers (AB) and 5alpha-reductase inhibitors (5ARIs), alone or in combination (CT), for BPH-associated LUTS were analyzed. The 1-year and long term adherence together with the analyses of hospitalization rates for BPH and BPH-related surgery were examined using multivariable Cox proportional hazards regression model and Pearson chi square test.RESULTS: Patients exposed to at least 6 months of therapy had a 1-year overall adherence of 29 % (monotherapy AB 35 %, monotherapy 5ARI 18 %, CT 9 %). Patient adherence progressively declined to 15 %, 8 % and 3 % for AB, 5ARI, and CT, respectively at the fifth year of follow up. Patients on CT had a higher discontinuation rate along all the follow-up compared to those under monotherapy with ABs or 5ARIs (all p < 0.0001). Moreover, CT was associated with a reduced risk of hospitalization for BPH-related surgery (HR 0.94; p < 0.0001) compared to AB monotherapy.CONCLUSIONS: Adherence to pharmacological therapy of BPH-associated LUTS is low and varies depending on drugs class. Patients under CT have a higher likelihood of discontinuing treatment for a number of reasons that should be better investigated. Our study suggests that new strategies aiming to increase patient's adherence to the prescribed treatment are necessary in order to prevent BPH progression.