Cardiometabolic risk factors and early indicators of vascular dysfunction: a cross-sectional cohort study in South African adolescents

Hypertension among adolescents in sub-Saharan Africa: a systematic review

Introduction

Hypertension (HTN) among adolescents is common in high-income countries, and leads to increased premature cardiovascular diseases (CVD). In sub-Saharan Africa (SSA), the prevalence of HTN among adolescents, associated risk factors and CVD complications are not well-described. Such data is needed for planning public health programs to prevent premature CVD in SSA.

Methods

We systematically searched 5 databases (MEDLINE, Embase, Google Scholar, Web of Science, and African Index Medicus) from their establishment to December 2021. Key search terms were: adolescent, arterial hypertension, and names of the 48 countries in SSA. We used Covidence® to manage the search results. The review was registered in the Open Science Framework (OSF) https://osf.io/p5sbt/.

Results

We identified 4,008 articles out of which we screened 3,088 abstracts, and reviewed 583 full-text articles. We finally included 92 articles that were published between 1968 to December 2021. The majority were cross-sectional studies (80%) and conducted in school settings (78%). The risk of bias was low for 59 studies (64.1%), moderate for 29 studies (31.5%), and high for 4 studies (4.3%). Overall, the prevalence of HTN varied widely from 0.18% to 34.0% with a median (IQR) of 5.5% (3.1%, 11.1%). It was relatively higher in studies using automated blood pressure (BP) devices, and in studies defining HTN using thresholds based on percentile BP distribution for one's height, age, and sex. In addition, the prevalence of HTN was significantly higher in studies from Southern Africa region of SSA and positively correlated with the year of publication. Across studies, traditional risk factors such as age, sex, body mass index, and physical inactivity, were commonly found to be associated with HTN. In contrast, non-traditional risk factors related to poverty and tropical diseases were rarely assessed. Only three studies investigated the CVD complications related to HTN in the study population.

Conclusion

The prevalence of HTN among adolescents in SSA is high indicating that this is a major health problem. Data on non-traditional risk factors and complications are scarce. Longitudinal studies are needed to clearly define the rates, causes, and complications of HTN.

Systematic Review Registration

https://osf.io/p5sbt/, identifier (10.17605/OSF.IO/P5SBT).

Assessment of the Performance of Obesity Measures in the Screening of Hypertension in a South African Adolescent Population

Obesity is known to be one of the most significant risk factors for essential hypertension in childhood. However, whether obesity cut-offs may predict hypertension screening in adolescents remains controversial. This study investigated the performance of obesity cut-off values for the screening of hypertension in a South African adolescent population. In this cross-sectional study, 1144 adolescents aged between 11 and 17 years were recruited from the Eastern Cape Province of South Africa. Anthropometric and blood pressure (BP) parameters including diastolic blood pressure (DBP), systolic blood pressure (SBP), and heart rate (HR) were measured. Assessment of the sensitivity and specific of obesity cut-off values in predicting hypertension was performed using receiver operating characteristic (ROC) analysis. Obesity was positively associated (p < 0.01) with hypertension. Obese individuals, based on the predicted obesity using BMI percentile cut-off (pBMI85.2%), were more likely to develop hypertension (odds ratio: 2.070; p < 0.001) than their counterparts based on the observed obesity cut-off (pBMI95%) (Odd ratio: 1.748 p = 0.004). The area under the curve (AUC) of BMI percentile and WHtR for screening SBP percentile, and DBP percentile and HR as per ROC analysis, was low (<0.65). Equally, the sensitivity and specificity were low (<0.6) for all BP measures (SBP, DBP, and HR). Furthermore, the cut-off values for blood pressure measures, as established by ROC analysis using anthropometric measures, were far below the recommended cut-off values for hypertension screening. The obesity cut-offs for BMI percentile and WHtR established in this populations showed poor performance in diagnosing hypertension even though they were strong predictors of hypertension.

Detecting and Managing Childhood Onset Hypertension in Africa: A Call to Action

PURPOSE OF REVIEW

To review recent evidence on childhood hypertension across Africa, identifying knowledge gaps, challenges and priorities, and highlight clinical perspectives in managing primary hypertension.

RECENT FINDINGS

Only 15 of the 54 African countries reported on absolute blood pressure (BP) measures, elevated BP, pre- and/or hypertension. The reported hypertension prevalence ranged between 0.0 and 38.9%, while elevated BP and/or pre-hypertnesion ranged from 2.7 to 50.5%. Childhood BP nomograms are lacking across Africa and the rates of hypertension were based on guidelines developed in countries with the lowest to no number of children from African ancestry. The recent studies across Africa also showed little to no detail when reporting BP specific methodology. No recent data informing the use or effectiveness of antihypertensive agents in children and adolesents are available. Childhood hypertension is on the rise, while data from Africa remains vastly under-represented. Collaborative research, resources, and policies need to be strengthened in addressing the growing public health concern of childhood onset hypertension on this continent.

Disparities between determinants of impaired vascular structure and function in young people with primary hypertension: a systematic review

OBJECTIVE

Early effects of primary hypertension on arterial structure and function in children and young people (CYP) and their determinants remain elusive. We aimed to review independent determinants of carotid intima-media thickness (cIMT), carotid wall cross-sectional area (WCSA) and carotid-femoral pulse wave velocity (cfPWV) in CYP with primary hypertension.

METHODS

We performed a systematic review of studies reporting multivariable analysis of cfPWV, cIMT and WCSA in CYP (up to 25 years of age) with primary hypertension. Literature search was performed in PubMed database and 13, 12 and two articles including 3860 (age range 4-25 years, 50% male individuals), 2038 children (5-25 years, 55% male individuals) and 136 children (5-17 years, 85% male individuals) were selected for final analysis of cfPWV, cIMT and WCSA, respectively.

RESULTS

Ninety and 86% of the studies reported higher cfPWV and cIMT in CYP with elevated blood pressure (BP) compared with normotensive controls. Different indices of BP were positively associated with cfPWV in 92% of studies, whereas BMI showed association in 31%. Carotid IMT associated with BP indices in 50% and with BMI in 25% of the studies. WCSA was studied longitudinally and its improvement associated with decrease in measures of central obesity.

CONCLUSION

We found a disparity between the determinants of structural and functional impairment of arterial tree in CYP with primary hypertension. In contrast to cIMT and WCSA, increase of cfPWV is almost exclusively determined by BP.

Classification of African Native Plant Foods Based on Their Processing Levels

With increasing advocacy for plant food consumption, the sub-Saharan Africa landscape is home to diverse plant-based food commodities. The need to leverage the advantages of unprocessed/minimally processed foods (PFs) over ultra-processed foods (UPFs) is a system that requires exploitation. Most of the crops produced in the continent are either classified as traditionally or moderately PFs. However, the rise in industrialization and formalization of markets is impacting and marginalizing traditional food processing (FP). Current FP classification frameworks are briefly discussed. The level of processing of cereals, grains, fruits, vegetables, roots, and tuber crops in the continent requires intervention from nutritionists, food scientists, and scientific and governmental bodies to gain a holistic view and tackle the issue of food insecurity in Africa. This study reviews the levels of processing of African foods, challenges, and future directions.

Association between obesity and lung function in South African adolescents of African Ancestry

Background

There is a growing body of literature on the increasing prevalence of obesity in adolescents of Sub-Saharan African ancestry. However, limited data is available on the impact of obesity on pulmonary function. This study assessed the relationship between obesity and lung function in South African adolescents of African ancestry.

Methods

This was a cross-sectional study involving 10–14 year old adolescents recruited from middle schools of the Eastern Cape Province of South Africa. Anthropometric measurements were performed. Body mass index (BMI) was converted to percentiles for age and sex and used to classified obesity. Spirometry was performed to assess lung function. Chi-square test of association and binary regression analysis were used to assess the relationship between obesity and airway obstruction. Adjusted linear regression was used to determine the relationship between obesity and lung function parameters.

Results

A total of 540 adolescents were recruited for the study among which 77 (14.3%) were obese. Lung function parameters: forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV₁) were higher (p < 0.001) in obese than in non-obese adolescents while peak expiratory flow (PEF) % and FEV₁/FVC ratio were lower (p < 0.05) in obese than non-obese adolescents. Obesity was associated (χ2 = 9.614; p < 0.01) with airway obstruction and obese adolescents were over 1.5 times more likely to have pulmonary obstruction (OR: 1.57; p < 0.05) than their non-obese counterparts. Anthropometric measures were positively associated (p < 0.05) with FVC, FEV1, PEF and/or FEV_25-75 but negatively associated with FEV₁/FVC ratio.

Conclusions

Obesity was associated with airway obstruction in South Africa adolescents of African ancestry.

Assessment of the Cardiovascular Risk Profile of Infants Exposed to Pre-eclampsia in-utero: A Prospective Case-Control Study in South African Children of African Ancestry

Background: It has been reported that maternal gestational environment may be programmed to have a significant impact on foetal and offspring health later in life. Studies have shown that children born to pre-eclamptic mothers are prone to obesity, hypertension, and diabetes in their adult life. However, such findings are yet to be established in an African population. This protocol is for a study aiming to investigate the relationship between pre-eclampsia (PE) and cardiovascular risk in children born to pre-eclamptic mothers in a South African population of African descents.

Methods: A prospective case-control design will be employed to recruit pre-eclamptic and normotensive pregnant women and their offspring after birth. Pregnant women will be assessed for cardiovascular risk factors including PE, obesity, haemodynamics, lipids, glycaemic indices, oxidative stress, and vascular function at 30 weeks of gestation. The cardiovascular risk profile of their offspring will be assessed at birth and 6 weeks later. The difference in cardiovascular risk profile between children born to the pre-eclamptic and normotensive mothers will be compared and the correlation between maternal and offspring cardiovascular risks will be investigated.

Discussion: This will be the first prospective study to assess the in-utero effect of cardiovascular risk in offspring born to pre-eclamptic women of African ancestry. It is expected that findings from this study will provide information on the cardiovascular effect of in-utero exposure to PE in a population of African ancestry. This knowledge will advise policy on the management of women with PE with a view of protecting cardiovascular health in offspring.

Assessment of Anthropometric Indices for Optimal Cut-Offs for Obesity Screening in a South African Adolescent Population

Simple Summary

The diagnosis of obesity in sub-Saharan African children relies on cut-off values for body mass index percentile (pBMI) and waist-to-height ratio (WtHR) established in western populations. Hence, this study assessed anthropometric indices to determine optimal cut-off values for obesity screening in the South African adolescent population. Findings from this study showed that the cut-off value for pBMI was p85.2th, which improved the sensitivity of the test by approximately 30% compared to the CDC recommended BMI percentile of p95.0th. Moreover, the optimal cut-off for WHtR was 0.481, which was close to the recommended cut-off value of 0.5. This study reveals a lower pBMI cut-off value, different from the CDC recommended cut-off, for screening obesity in a South African adolescent population and suggests that the optimal pBMI cut-off for obesity screening may be ethnic-specific.

Abstract

The assessment of obesity in sub-Saharan Africa relies on cut-offs established from western populations. This study assessed anthropometric indices to determine optimal cut-off values for obesity screening in the South African adolescent population. A cross-sectional study involving 1144 (796 females and 348 males) adolescents aged 11–17 years from the Eastern Cape Province of South African was conducted. Anthropometric parameters were measured. Receiver operating characteristic (ROC) analysis was performed to assess the sensitivity and specificity of obesity screening tools and establish cut-offs. The optimal cut-offs for obesity in the cohort using waist-to-height ratio (WHtR) as reference were: neck circumference (NC) = 30.6 cm, mid-upper arm circumference (MUAC) = 25.9 cm, waist circumference (WC) = 75.1 cm, hip circumference (HC) = 92.15 cm and body mass index percentile (pBMI) = p85.2th. The new pBMI cut-off value at p85.2th improved the sensitivity of the test by approximately 30% compared to the CDC recommended BMI percentile (pBMIr) of p95.0th. When pBMI was used as reference, the optimal cut-offs in the cohort were: WHtR = 0.481, NC = 30.95 cm, MUAC = 27.95 cm, WC = 76.1 cm and HC = 95.75 cm. The WHtR optimal cut-off of 0.481 was close to the recommended cut-off value of 0.5. The predicted prevalence of obesity obtained using cut-offs from ROC analysis was higher than those from recommended references. All cut-off values for the various anthropometric measures generally increased with age for all percentile ranges. This study reveals a lower pBMI cut-off value, different from the CDC recommended cut-off, for screening obesity in a South African adolescent population. The study has established that the optimal pBMI cut-off for obesity screening may be ethnic-specific.

Autoimmune Rheumatic Diseases and Vascular Function: The Concept of Autoimmune Atherosclerosis

Autoimmune rheumatic diseases (AIRDs) with unknown etiology are increasing in incidence and prevalence. Up to 5% of the population is affected. AIRDs include rheumatoid arthritis, system lupus erythematosus, systemic sclerosis, and Sjögren's syndrome. In patients with autoimmune diseases, the immune system attacks structures of its own body, leading to widespread tissue and organ damage, which, in turn, is associated with increased morbidity and mortality. One third of the mortality associated with autoimmune diseases is due to cardiovascular diseases. Atherosclerosis is considered the main underlying cause of cardiovascular diseases. Currently, because of finding macrophages and lymphocytes at the atheroma, atherosclerosis is considered a chronic immune-inflammatory disease. In active inflammation, the liberation of inflammatory mediators such as tumor necrotic factor alpha (TNFa), interleukine-6 (IL-6), IL-1 and other factors like T and B cells, play a major role in the atheroma formation. In addition, antioxidized, low-density lipoprotein (LDL) antibodies, antinuclear antibodies (ANA), and rheumatoid factor (RF) are higher in the atherosclerotic patients. Traditional risk factors like gender, age, hypercholesterolemia, smoking, diabetes mellitus, and hypertension, however, do not alone explain the risk of atherosclerosis present in autoimmune diseases. This review examines the role of chronic inflammation in the etiology-and progression-of atherosclerosis in autoimmune rheumatic diseases. In addition, discussed here in detail are the possible effects of autoimmune rheumatic diseases that can affect vascular function. We present here the current findings from studies that assessed vascular function changes using state-of-the-art techniques and innovative endothelial function biomarkers.

A Pilot Study: Hypertension, Endothelial Dysfunction and Retinal Microvasculature in Rheumatic Autoimmune Diseases

Background: The etiology of autoimmune rheumatic diseases is unknown. Endothelial dysfunction and premature atherosclerosis are commonly seen in these patients. Atherosclerosis is considered one of the main causes of cardiovascular diseases. Hypertension is considered the most important traditional cardiovascular risk. This case-control study aimed to investigate the relationship between autoimmune diseases and cardiovascular risk. Methods: This study was carried out in patients with rheumatoid arthritis, RA (n = 10), primary Sjögren syndrome, PSS (n = 10), and healthy controls (n = 10). Mean blood pressure (MBP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse wave velocity (PWV, an indicator of arterial stiffness) were assessed via a Vicorder device. Asymmetric dimethylarginine (ADMA) was measured via ELISA. Retinal photos were taken via a CR-2 retinal camera, and retinal microvasculature analysis was carried out. T-tests were conducted to compare the disease and control groups. ANOVA and ANOVA—ANCOVA were also used for the correction of covariates. Results: A high prevalence of hypertension was seen in RA (80% of cases) and PSS (40% of cases) compared to controls (only 20% of cases). Significant changes were seen in MBP (RA 101 ± 11 mmHg; PSS 93 ± 10 mm Hg vs. controls 88 ± 7 mmHg, p = 0.010), SBP (148 ± 16 mmHg in RA vs. 135 ± 16 mmHg in PSS vs. 128 ± 11 mmHg in control group; p = 0.007), DBP (77 ± 8 mmHg in RA, 72 ± 8 mmHg in PSS vs. 67 ± 6 mmHg in control; p = 0.010 in RA compared to the controls). Patients with PSS showed no significant difference as compared to controls (MBP: p = 0.240, SBP: p = 0.340, DBP: p = 0.190). Increased plasma ADMA was seen in RA (0.45 ± 0.069 ng/mL) and PSS (0.43 ± 0.060 ng/mL) patients as compared to controls (0.38 ± 0.059 ng/mL). ADMA in RA vs. control was statistically significant (p = 0.022). However, no differences were seen in ADMA in PSS vs. controls. PWV and retinal microvasculature did not differ across the three groups. Conclusions: The prevalence of hypertension in our cohort was very high. Similarly, signs of endothelial dysfunction were seen in autoimmune rheumatic diseases. As hypertension and endothelial dysfunction are important contributing risk factors for cardiovascular diseases, the association of hypertension and endothelial dysfunction should be monitored closely in autoimmune diseases.

COVID-19 and its effects on endothelium in HIV-positive patients in sub-Saharan Africa: Cardiometabolic risk, thrombosis and vascular function (ENDOCOVID STUDY)

BACKGROUND

COVID-19 has affected almost every country in the world, especially in terms of health system capacity and economic burden. People from sub-Saharan Africa (SSA) often face interaction between human immunodeficiency virus (HIV) infection and non-communicable diseases such as cardiovascular disease. Role of HIV infection and anti-retroviral treatment (ART) in altered cardiovascular risk is questionable and there is still need to further carry out research in this field. However, thus far it is unclear, what impact the COVID-19 co-infection in people living with HIV (PLHIV), with or without therapy will have. The ENDOCOVID project aims to investigate whether and how HIV-infection in COVID-19 patients modulates the time course of the disease, alters cardiovascular risk, and changes vascular endothelial function and coagulation parameters/ thrombosis risk.

METHODS

A total of 1026 patients will be included into this study. Cardiovascular research PLHIV with (n = 114 in each of the three recruiting centers) - or without - ART (n = 114 in each of the three recruiting centers) with COVID-19 and HIV-negative with COVID-19 (n = 114 in each of the three recruiting centers) will be carried out via clinical and biochemical measurements for cardiovascular risk factors and biomarkers of cardiovascular disease (CVD). Vascular and endothelial function will be measured by brachial artery flow-mediated dilatation (FMD), carotid intima-media thickness (IMT) assessments, and retinal blood vessel analyses, along with vascular endothelial biomarkers and cogualation markers. The correlation between HIV-infection in COVID-19 PLHIV with or without ART and its role in enhancement of cardiovascular risk and endothelial dysfunction will be assessed at admission, weekly, at discharge and, 4 weeks post-discharge (if possible).

IMPACT OF PROJECT

The ENDOCOVID project aims to evaluate in the long-term the cardiovascular risk and vascular endothelial function in PLHIV thus revealing an important transitional cardiovascular phenotype in COVID-19. The study was registered under clinicaltrials.gov (NCT04709302).

Assessment of the impact of HIV infection and anti-retroviral treatment on the cardiometabolic health of pregnant mothers and their offspring (ARTMOMSBABES)

BACKGROUND

The risk of cardiovascular diseases (CVDs) is becoming more prevalent in pregnant women though not much data is available for pregnant women with human immunodeficiency virus (HIV). Foetoplacental vascular endothelial dysfunction is thought to be at the origin of chronic diseases such as diabetes and obesity later on in life. Because HIV and anti-retroviral treatment (ARTs) are associated with endothelial dysfunction, children exposed in utero to these conditions may be at greater risk of developing CVDs. Despite the high prevalence of HIV in pregnant South African women, little is known about the effects of ART on the cardiovascular health of the mother and offspring. Hence, the proposed study intends to investigate how HIV/ARTs may affect the cardiovascular health of the mother and offspring at different time points during the pregnancy and up to 2 years after birth.

METHODS

A longitudinal case-control study in HIV positive pregnant women on ART and HIV negative pregnant women will be conducted. All pregnant women will be assessed for cardio-metabolic risk factors and markers (lipids, anthropometric and glycaemic indies, oxidative stress), hemodynamic status (blood pressure parameters) and vascular function (arterial compliance, retinal microvasculature, uterine artery mean pulsatility index). Child health will be monitored in utero and postnatally via routine foetal health screening, placental integrity, anthropometry, blood pressure parameters, markers of oxidative stress and endothelial function in cord blood and cardiovascular epigenetic markers in urine.

DISCUSSION

There is a paucity of studies in South Africa and sub-Sahara Africa as a whole that utilised a longitudinal study model to assess the effects of ARTs on vascular endothelial changes in pregnant women living with HIV and the cardiometabolic health of their offspring. This study will therefore help to monitor changes in cardiometabolic risk during pregnancy and in children exposed in utero to HIV-infection and ART use. Findings from this study will provide useful information for developing guidelines on the use of ARTs in pregnancy and management of cardiometabolic health of the offspring of HIV positive mothers.

Subcutaneous Adipose Tissue Measured by B-Mode Ultrasound to Assess and Monitor Obesity and Cardio-Metabolic Risk in Children and Adolescents

Simple Summary

The prevention and treatment of childhood and adolescent overweight and obesity raises the need for accurate body fat assessment. Precise methods are at high technical expense, require exposure to ionizing radiation and are limited to institutional investigations, while common body indicators fail to identify excess body fat. Subcutaneous adipose tissue measured by ultrasound is an alternative approach, which was evaluated in relation to commonly applied body indicators to assess cardio–metabolic risk and its applicability in the field. Subcutaneous adipose tissue measured by ultrasound indicated a clear advantage over commonly applied body indicators and implies that severe body fat assessment errors are to be expected when BMI is used as a measure for body fatness in children. Children or adolescents with identical BMIs may have large differences (>200%) in their amount of subcutaneous adipose tissue. Ultrasound provides an easily applicable, reliable and safe method for accurate assessment of obesity and monitoring treatment responses in children and adolescents at cardio–metabolic risk.

Abstract

Monitoring of children at heightened risk of cardio–metabolic diseases raises the need for accurate assessment of obesity. A standardized approach for measuring subcutaneous adipose tissue (SAT) by bright-mode ultrasound was evaluated in relation to body indices and anthropometry in a cross-sectional sample of 76 South African children (7–10 years) and 86 adolescents (13–17 years) to assess cardio–metabolic risk. SAT was higher in girls as compared to boys (children: 50.0 ± 21.7 mm > 34.42 ± 15.8 mm, adolescents: 140.9 ± 59.4 mm > 79.5 ± 75.6 mm, p < 0.001) and up to four times higher in adolescents than in children. In children, measures of relative body weight showed only a poor correlation to SAT (BMI: r = 0.607, p < 0.001), while in adolescents, BMI correlated high with SAT (r = 0.906, p < 0.001) based on high rates of overweight and obesity (41.8%). Children with identical BMIs may have large differences (>2–3-fold) in their amount of SAT. The moderate association to systolic (r = 0.534, r = 0.550, p < 0.001) and diastolic blood pressure (r = 0.402, r = 0.262, p < 0.001) further substantiates that SAT measured by ultrasound provides an accurate, safe and easy applicable approach for monitoring in children and adolescents at cardio–metabolic risk.

An Overview of Vascular Dysfunction and Determinants: The Case of Children of African Ancestry

The balance between dilatory and constrictive factors is important as it keeps blood vessels in a homeostatic state. However, altered physiological processes as a result of obesity, hypertension, oxidative stress, and other cardiovascular risk factors may lead to vascular damage, causing an imbalance of vasoactive factors. Over time, the sustained imbalance of these vasoactive factors may lead to vascular dysfunction, which can be assessed by non-invasive methods, such as flow-mediated dilation, pulse wave velocity, flow-mediated slowing, retinal vessel analysis, peripheral vascular reactivity, and carotid intima-media thickness assessment. Although there is increasing prevalence of cardiovascular risk factors (obesity and hypertension) in children in sub-Saharan Africa, little is known about how this may affect vascular function. This review focuses on vasoactive factors implicated in vascular (dys)function, highlighting the determinants and consequences of vascular dysfunction. It further describes the non-invasive methods used for vascular (dys)function assessments and, last, describes the impact of cardiovascular risk factors on vascular dysfunction in children of African ancestry.