Lack of association of glycated haemoglobin with blood pressure and subclinical atherosclerosis in black South Africans: a five-year prospective study

  • Anna S E Koegelenberg North-West University
  • Annamarie Kruger North-West University
  • G Wayne Towers North-West University
  • Aletta E Schutte North-West University
Keywords: Fasting glucose, Chronic glucose, Ethnicity, Atherosclerosis, Longitudinal

Abstract

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.

Author Biographies

Anna S E Koegelenberg, North-West University
MSc Postgraduate Research Student Hypertension in Africa Research Team (HART) North-West University Potchefstroom
Annamarie Kruger, North-West University
PhD Director Africa Unit for Transdisciplinary Health Research North-West University Potchefstroom
G Wayne Towers, North-West University
PhD Senior Lecturer Centre of Excellence for Nutrition North-West University Potchefstroom
Aletta E Schutte, North-West University
PhD Professor of Physiology Hypertension in Africa Research Team (HART) North-West University Potchefstroom
Published
2013-07-25
Section
Original Research