OBJECTIVES: To investigate the risk of ASCVD among Taiwan diabetes patients who were non-adherent or stopped statin treatments, as compared with those who were adherent to statin treatments,. METHODS: Using Taiwan National Health Insurance claims 2003—2011, we identified a retrospective cohort of incident diabetes patients aged above 40 years who received statin treatments. Patients were followed from the first date they received statin after diabetes diagnosis (the index date) till restart of statins, ASCVD occurred, death, or the end of the study (2013/12/31). Time-varying adherence and covariates were assessed and followed quarterly (in fixed 3-month windows). Patients were classified into adherent (MPR>=80%), non-adherent (MPR<80%) and stop groups based on Medication Possession Ratio (MPR) in each window. Marginal structure models (MSM) with stabilized weights were used to assess the association between non-adherence or stop and ASCVD, adjusting for baseline and time-varying confounders, and using adherent patients as the reference group. RESULTS: There were 273,461 statin initiators after diabetes diagnosis, and 62.5% of them were adherent in the first 3-month window. Adherent patients were more likely to receive lipid level tests, treated at higher tiers of medical facilities, and lived in higher urbanization cities during the follow-up. After stabilizing both baseline and time-varying confounders across time, the risks of ASCVD for patients non-adherent or stop treatments increased by 2.2-2.4 fold (HR for non-adherent: 2.27; 95%CI: 2.15-2.38; HR for stop: 2.41; 95%CI: 2.29-2.55), as compared with patients being adherent. We also found traditional methods included only baseline confounders may underestimate the association of being non-adherent or stop (HR for non-adherent: 1.84; 95%CI: 1.78-1.91; HR for stop: 1.27; 95%CI: 1.23-1.30). CONCLUSIONS: After adjusting for both baseline and time-varying confounders, we found diabetes patients non-adherent or stop their statin treatments may increase their risk for ASCVD more than two-folds, as compared with adherent patients.