BACKGROUND : The use of statins has been associated with improved survival in patients with breast cancer in several studies but results have been mixed. This study evaluates the impact of duration of statin use on breast cancer patient outcomes. METHODS : This is a single-institution, retrospective cohort, examining the impact of statin use on the outcomes of 1523 women diagnosed with operable breast cancer between1995 and 2015. Clinical variables were compared using Student's t test, Fisher's exact and Chi square tests. Overall (OS) and disease-free (DFS) survival were performed using Kaplan-Meier and Cox-Proportional Hazard (Cox-PH) analysis in the statistical software R. RESULTS : Patients were grouped by duration of statin use: never-statin user [N] (n = 1092), short (< 3 years) [S] (n = 115), moderate [M] (3-5 years) (n = 109) and long [L] (> 5 years) (n = 207) term. Over a median follow-up of 70.2 months, 138 women died (84 died of breast cancer) and 125 had disease recurrence. On multivariable Cox-PH analysis adjusting for clinical variables including metabolic comorbidities using the Charlson comorbidity index, OS in the [S] and [M] subgroups did not differ [N], while OS was improved in [L] (adjusted hazard ratio (AHR) 0.38, confidence interval (CI) 0.17-0.85, p < 0.018). DFS was also significantly improved in the [L] subgroup (adjusted HR 0.15, CI 0.05-0.48, p < 0.001). Subanalysis stratified by receptor status showed a trend towards improved DFS in all tumor subtypes including triple-negative breast cancer. CONCLUSIONS : Our retrospective analyses suggest that long-term statin use (> 5 years) was associated with improved OS and DFS in women with breast cancer regardless of receptor subtype, even after adjusting for metabolic comorbidities.