Haemoglobin A1c is associated with carotid intima-media thickness in a Chinese population

Background The association between haemoglobin A1c (HbA1c) levels and subclinical atherosclerosis in carotid arteries in Chinese populations is unknown. Aim, design and methods The objective of this study was to investigate this relationship and evaluate the ability of HbA1c levels to predict carotid atherosclerosis in a Chinese population. This was a cross-sectional study, which included 541 subjects without known diabetes (Taiwan Lifestyle Study). About 67 (9.2%) subjects were newly diagnosed with diabetes during the study. Carotid intima-media thickness (IMT) and the presence of carotid plaques were determined using ultrasonography. Results The HbA1c level in all subjects was positively correlated with carotid IMT (beta = 0.018, P = 0.03) after being adjusted for age, gender, smoking, low-density lipoprotein cholesterol level, hypertension and body mass index. HbA1c level was higher in subjects with plaques in carotid arteries (P = 0.01). There was a positive and linear relationship between HbA1c levels and the probability of having plaques, thickened carotid IMT or both (P for all comparisons, < 0 05). The ability of HbA1c levels to predict thickened carotid IMT or the presence of plaques was only modest {the optimal cutoff of HbA1c level [5.7%] was determined from the receiver operating characteristic (ROC) curve (sensitivity = 67%, specificity = 61%) and the area under the ROC curve [0.666]}. Conclusions Thus, HbA1c level is associated with subclinical atherosclerosis in carotid arteries in a Chinese population. The relationship is linear without an inflection point. However, HbA1c criterion is not a useful marker for the identification of subclinical atherosclerosis.