AimTo investigate the association between plasma lipids and presence of unstable carotid plaques in middle-aged and elderly people with carotid plaques.MethodsTwo hundred and seventy patients with carotid plaques detected by B-mode ultrasonography were enrolled in the study and divided into the unstable plaque group(n=130) and the control group(n=140).The plasma lipid levels were also determined in all subjects.ResultsAfter the adjustment of age, gender, hypertension, diabetes and smoking, the Logistic analysis revealed that the following lipid parameters are associated with unstable carotid plaque: Non-HDLC(OR=1.27,95%CI 1.02～1.58, p=0.032), TC/LDLC(OR=1.67,95%CI 1.17～2.38, p=0.005), apoB(OR=4.53, 95%CI 1.21～16.94, p=0.025) and apoB/apoA1(OR=17.85,95%CI 3.63～87.87, p<0.001) .Among them, apoA1 was the protective factor of unstable carotid plaque, while the others were risk factors.In addition, apoB/apoA1 was determined as the independent risk factor of the presence of unstable carotid plaque.ConclusionsThese results suggest that apoB/apoA1 can be used as an independent predictive index to assess the risk of unstable carotid plaque formation in middle-aged and elderly people.