BACKGROUND: Low-density lipoprotein cholesterol (LDL-C) and type 2 diabetes (T2DM) are both independent risk factors for aortic stenosis (AS). In AS patients, whether LDL-C or T2DM is associated with fast AS progression (FASP) and their interaction is unknown. This study aims to test the hypothesis that there is a heightened risk of FASP when elevated LDL-C coexists with T2DM. METHODS: The Real-world Data of Cardiometabolic Protections (RED-CARPET) study enrolled participants with mild (peak aortic velocity = 2-3 m/s), moderate (3-4 m/s) and severe ( 4 m/s) AS between January 2015 and December 2020 at a single center. Participants were further stratified by baseline LDL-C joint T2DM, follow-up echocardiography was performed after 6 months, and the primary outcome was FASP, defined as the annual change in aortic peak velocity ( 0.3 m/s/year). RESULTS: Among the 170 participants included, 45.3% had mild AS, 41.2% had moderate AS, and 13.5% had severe AS. The mean age was 66.84 12.64 years, and 64.1% were women. During the follow-up period of 2.60 1.43 years, 35 (20.6%) cases of FASP were identified. Using non-T2DM with LDL-C 2.15 mmol/L as reference, FASP risk was 1.30 [odds ratio (OR), 95% CI (0.99-7.78, = 0.167)] for non-T2DM with LDL-C 2.15-3.14 mmol/L, 1.60 [OR, 95% CI (1.17-3.29, = 0.040)] for non-T2DM with LDL-C 3.14 mmol/L, 2.21 [OR, 95% CI (0.49-4.32, = 0.527)] for T2DM with LDL-C 2.15 mmol/L, 2.67 [OR, 95% CI (1.65-7.10, = 0.004)] for T2DM with LDL-C 2.15-3.14 mmol/L, and 3.20 [OR, 95% CI (1.07-5.34, = 0.022)] for T2DM with LDL-C 3.14 mmol/L. CONCLUSIONS: LDL-C joint T2DM was associated with FASP. This investigation suggests that fast progression of AS may develop if LDL-C is poorly managed in T2DM. Additional research is needed to validate this finding and explore the possible biological mechanism to improve the cardiometabolic management of T2DM and seek possible prevention for AS progression for this population. CLINICAL TRIAL REGISTRATION: ChiCTR2000039901 (https://www.chictr.org.cn).