Lack of Association of Glycated Haemoglobin with Blood Pressure and Subclinical Atherosclerosis in Black South Africans: a Five-Year Prospective Study

Objectives: Hypertension and diabetes are common in rapidly urbanising sub-Saharan African communities. However; lack of longitudinal data in these regions prevents adequate analysis of the link between measures of glycaemia and cardiovascular disease. Therefore; we examined the relationships of fasting glucose and glycated haemoglobin (HbA1c) with brachial and central blood pressure (BP); and measures of vascular structure and function after five years in black South Africans.Setting and subjects: Nine hundred and twenty-eight participants were included as part of the Prospective Urban Rural Epidemiological (PURE) study in the North West Province.Outcome measures: Fasting glucose; HbA1c and brachial BP at two time points were determined. Central BP; augmentation index (AI) and carotid intima-media thickness (CIMT) were taken at follow-up. Results: Fasting glucose [4.78 (3.50; 6.30) vs. 5 mmol/l (3.96; 6.42)]; HbA1c [5.6 (4.9; 6.3) vs. 5.9 (5.2; 6.9) and (37 vs. 41 mmol/mol)]; and BP (134/88.1 vs. 138/89.5 mmHg) increased significantly over five years (p-value 0.05). However; an association was absent between BP; AI or CIMT and either baseline or the five-year change in glucose or HbA1c. Multivariate analyses confirmed that neither glucose or HbA1c predicted changes in BP; CIMT or AI; but factors that did associate significantly were age; male gender; rural location; abdominal obesity; alcohol intake; total cholesterol to high-density lipoprotein ratio; C-reactive protein and antihypertensive medication (R2; ranging from 0.24-0.36).Conclusion: Although both BP and measures of glycaemia increased significantly over five years in black South Africans; glucose was not independently associated with BP or measures of large artery structure or function. We suggest that fasting glucose and HbA1c below the threshold of diagnosing diabetes should not be used in isolation to predict cardiovascular risk in African individuals

Iron status and cardiovascular disease risk in black South African women: the PURE study

Objective: To examine the associations between measures of iron status and cardiovascular disease (CVD) risk factors in South African women.Method: In a cross-sectional study; demographic information and health history were obtained during individual interviews using validated questionnaires in the North West Province; South Africa. Anthropometric indices; iron indices; blood pressure; blood glucose and lipid profiles were measured using standard procedures in 1 262 apparently healthy black South African women aged 35 years or older. Iron status was assessed using serum concentrations of ferritin; transferrin receptor (TfR) and TfR:ferritin ratio.Results: Associations between iron status parameters and CVD risk factors were generally weak (r 0.3; p 0.01) and were not retained when adjustment was made for age; body mass index; smoking; alcohol consumption and C-reactive protein in the analysis. Waist circumference (WC) and waist:hip ratio (WHR) were higher in the fourth quartile of serum ferritin than in the third quartile; and also in the third quartile compared to the second quartile (P 0.05). Based on WC and WHR respectively; 31 and 52of the women had excess abdominal obesity. The mean (95 confidence interval) serum TfR concentration was high; at 9.09 ?g/ml (8.77; 9.44); indicating risk of iron deficiency. The mean (95 confidence interval) concentrations of lipids [total cholesterol 4.78 mmol/l (4.64; 4.93); high-density lipoprotein cholesterol 1.45 mmol/l (1.39; 1.52); low-density lipoprotein cholesterol 1.65 mmol/l (1.53; 1.78); triglyceride 1.12 mmol/l (1.07; 1.18)] were within reference ranges.Conclusion: No significant association was found between iron status parameters and established CVD risk factors. However; excessive abdominal adiposity indicated by high WC and WHR contributes significantly to increased serum ferritin concentration in this population