Background
Non-communicable diseases (NCDs) are the leading causes of illness and death worldwide. They accounted for 71% of overall mortality, in 2016, while cardiovascular diseases (CVD) and diabetes were responsible for almost half (47.6%) of the NCD burden.1 The majority of premature deaths from NCDs (85%) occur in low-income to middle-income countries,1 where health systems are struggling to cope with the concurrent problems of infectious diseases and emerging NCDs. In South Africa, the rapidly increasing prevalence of NCDs contributes to the multiple burden of disease, comprising tuberculosis and HIV, ongoing malnutrition, and high maternal and child mortality.2 3 Diabetes and CVD have been the second and third leading causes of death in the country since 2014,4 highlighting the need to prioritize their prevention. One prevention strategy could be through identification of high-risk populations and offering tailored interventions.
Recent South African epidemiologic surveys show that at least a quarter of pregnant women (26%) have hyperglycemia first detected in pregnancy (HFDP),5 while almost 10% have gestational diabetes mellitus (GDM).6 This may increase their risk for early CVD. However, as the risk factor-based screening currently being used in South Africa is suboptimal, a significant proportion of pregnant women are not screened for HFDP.5 7 Until recently, GDM was defined as HFDP with a postpartum return to normalcy in many guidelines. Further, the criteria used for the diagnosis of GDM have varied widely in different countries. However, the WHO 2013 guidelines,8 which were largely based on the results of the Hyperglycemia and Adverse Pregnancy Outcomes Study,9 and the recommendations of the International Association of Diabetes and Pregnancy Study Groups10 have been adopted by many regional and national bodies. These WHO guidelines include the adoption of lower fasting glucose cut-offs and the distinction between GDM and diabetes in pregnancy (DIP), where blood glucose concentrations are diagnostic of type 2 diabetes mellitus.
Meta-analyses have shown that women with a history of GDM (although these studies also included women with DIP, according to the WHO 2013 criteria) have double the risk for overall CVD11 12 and coronary artery disease in the long term12 and four times the risk for metabolic syndrome,13 compared with women with normoglycemic pregnancies.13 There may be population differences in the association between GDM and metabolic syndrome, as Asian studies did not show the association seen with other populations. Although metabolic syndrome’s utility as a clinical entity is debatable, it represents a constellation of risk factors for CVD, with possible common pathophysiology and common environmental risk factors. Insulin resistance, thought to be central in the development of metabolic syndrome,14 is also associated with beta-cell deterioration during the immediate post-HFDP period15 and consequent progression to type 2 diabetes.16
To the best of our knowledge, there are no published studies on the intermediate and long-term burden of CVD in African women post-HFDP, despite the increasing understanding of the critical role women of childbearing age play in the possible intergenerational transmission of and prevention of CVD risk. The aim of this study was to describe the prevalent metabolic syndrome, insulin resistance and individual CVD risk factors (raised blood pressure, dysglycemia, dyslipidemia, raised waist circumference, and overweight and obesity) and their risk factors in women 6 years post-HFDP in Cape Town, South Africa. We also compared the prevalence of metabolic syndrome and individual CVD risk factors between GDM and DIP groups, after reclassifying HFDP, post hoc, using modified WHO 2013 criteria.