ObjectiveTo investigate the impact of clopidogrel resistance on the long-term prognosis in the elderly with acute coronary syndrome (ACS), as clopidogrel is widely used for secondary prevention in the patients with ACS, while studies on the relationship between clopidogrel resistance and long-term outcome in the elderly with ACS are limited. MethodsThree hundred elderly patients with ACS, aged from 70 to 95, with on average age of (81.3±6.4) years old, receiving clopidogrel (75 mg, once a day) over one month between January 2009 and December 2010 were followed up for major adverse cardiac events (MACE, including cardiac death, non-fatal re-myocardial infarction, angina, ischemia stroke/TIA, acute thrombosis and hemorrhage). Platelet aggregation was measured by light transmission aggregometry using adenosine diphosphate as a stimulus. According to the variation of platelet aggregation, the patients were divided into clopidogrel resistance group (<10%) and non-lopidogrel resistance group (≥10%). The median follow-up was 2 years. A Cox hazard proportional model was used to estimate time to outcome associated with clopidogrel resistance and MACE. ResultsThe incidence of clopidogrel resistance was 24.0% in our study population. Patients with diabetes, renal insufficiency, or a higher body mass index tended to have clopidogrel resistance. Compared with those patients without clopidogrel resistance, there was significantly increased MACE in patients with clopidogrel resistance (37.5%, 22.8%; P=0.032). Additionally, Cox hazard proportional model analysis demonstrated that clopidogrel resistance was an independently risk factor for MACE[HR=2.34, 95% CI (1.07, 4.57), P=0.016]. ConclusionDiabetes, renal insufficiency and high body max index are associated with clopidogrel resistance, which can predict the increased risk of MACE in elderly patients with ACS.