Carotid artery intimal medial thickness, brachial artery flow-mediated vasodilation and cardiovascular risk factors in diabetic and non-diabetic indigenous Australians

Abstract

Background: Indigenous Australians are at high risk for cardiovascular disease and type 2 diabetes. Carotid artery intimal medial thickness (CIMT) and brachial artery flow-mediated vasodilation (FMD) are ultrasound imaging based surrogate markers of cardiovascular risk. This study examines the relative contributions of traditional cardiovascular risk factors on CIMT and FMD in adult Indigenous Australians with and without type 2 diabetes mellitus. Method: One hundred and nineteen Indigenous Australians were recruited. Physical and biochemical markers of cardiovascular risk, together with CIMT and FMD were meausred for all subjects. Results: Fifty-three Indigenous Australians subjects (45%) had type 2 diabetes mellitus. There was a significantly greater mean CIMT in diabetic versus non-diabetic subjects ( p = 0.049). In the non-diabetic group with non-parametric analyses, there were significant correlations between CIMT and: age ( r = 0.64, p < 0.001), systolic blood pressure ( r = 0.47, p < 0.001) and non-smokers ( r = −0.30, p = 0.018). In the diabetic group, non-parametric analysis showed correlations between CIMT, age ( r = 0.36, p = 0.009) and duration of diabetes ( r = 0.30, p = 0.035) only. Adjusting for age, sex, smoking and history of cardiovascular disease, Hb A1c became the sole significant correlate of CIMT ( r = 0.35, p = 0.01) in the diabetic group. In non-parametric analysis, age was the sole significant correlate of FMD ( r = −0.31, p = 0.013), and only in non-diabetic subjects. Linear regression analysis showed significant associations between CIMT and age ( t = 4.6, p < 0.001), systolic blood pressure ( t = 2.6, p = 0.010) and Hb A1c ( t = 2.6, p = 0.012), smoking ( t = 2.1, p = 0.04) and fasting LDL-cholesterol ( t = 2.1, p = 0.04). There were no significant associations between FMD and examined cardiovascular risk factors with linear regression analysis Conclusions: CIMT appears to be a useful surrogate marker of cardiovascular risk in this sample of Indigenous Australian subjects, correlating better than FMD with established cardiovascular risk factors. A lifestyle intervention programme may alleviate the burden of cardiovascular disease in Indigenous Australians by reducing central obesity, lowering blood pressure, correcting dyslipidaemia and improving glycaemic control. CIMT may prove to be a useful tool to assess efficacy of such an intervention programme.