The effects of cholesterol and obesity on carotid intima media thickness in a population of African ancestry

Moekanyi Jeffrey Sibiya A dissertation submitted to the Faculty of Health Sciences, University ofthe Witwatersrand, for the degree of Master of Science in Medicine. Johannesburg,2012Cholesterol is an important determinant of atherogenesis. However, populations of African ancestry have low total and LDL cholesterol concentrations (anti-atherogenic), but elevated triglyceride concentrations and low HDL concentrations (pro-atherogenic). The role of circulating lipids in atheroma formation in groups of African descent is uncertain. Therefore, in the current study I evaluated whether circulating lipids are independently associated with carotid intima media thickness (C-IMT), a surrogate marker of atheroma, in an urban developing community of African ancestry in SOWETO South Africa. 430 participants were randomly selected. C-IMT was determined from Doppler images of the carotid artery using a SonoSite (SonoCalc ™ IMT) version 3.4 device. In bivariate analysis total cholesterol, total:HDL cholesterol ratio, LDL cholesterol and triglyceride concentrations were all associated witp C-IMT (r=0.24 to r=0.26, p-values <0.0001) as were all indices of obesity (r= 0.16 to 0.30, p<0.001). However, in multivariate models which included adjustments for age, clinic systolic blood pressure, diabetes mellitus, smoking, treatment for hypertension, regular alcohol intake, heart rate and postmenopausal status (in women) neither the lipid variables nor the indices of obesity remained associated with C-IMT (total cholesterol r=-0.01, p=0.884; LDL r=0.02, p=0.682; TRGL r=-0.01, p=0.832; HDL r=-0.04, p=0.371; total:HDL cholesterol ratio r=0.02, p=684). In multivariate regression analysis only age (p<0.0001) and gender (p< 0.05) were independently associated with C-IMT. In conclusion, the current study shows that in an urban developing community of African ancestry with low cholesterol concentrations and a high prevalence of obesity there is no independent relationship between either circulating lipid concentrations and C-IMT or measures of obesity and C-IMT. However, age and gender independently predicted C-IMT in this population