Factor analysis of possible risks for hypertension in a black South African population

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).

Rising prevalence, and improved but suboptimal management, of hypertension in South Africa: A comparison of two national surveys

Aim

To examine the changes in prevalence, awareness, treatment and control of hypertension between 1998 and 2016 in ≥15-year-old South African men and women and the sociodemographic characteristics associated with those changes.

Methods

In nationally representative surveys in 1998 and 2016, multi-stage sampling was used to select, interview and collect blood pressure and anthropometric measurements in ≥15-year-old adults. Logistic regression analyses evaluated the independent effects of selected sociodemographic characteristics on hypertension management.

Results

Among 13,217 participants in 1998 and 7830 in 2016 (59-60% women in both surveys), hypertension prevalence increased from 27% to 45% in men and 31% to 48% in women. Hypertension increased equally in participants with and without obesity and in daily cigarette smokers vs. their counterparts. Prevalence of awareness among participants with hypertension increased from 7% to 18% (men) and from 17% to 29% (women). Among those aware, hypertension treatment improved markedly from 8% to 85% (men) and from 12% to 82% (women). Hypertension control among those on treatment increased from 17% to 26% (men) and from 21% to 30% (women). Increasing age and survey year were consistently associated with higher prevalence, awareness, treatment and control of hypertension. The richest vs. poorer women, and lower vs. higher educated women were more likely to be treated for hypertension.

Conclusions

The high and rising hypertension burden together with suboptimal awareness and control levels warrant greater attention to curb hypertension-related morbidity and mortality in South Africans. Novel strategies involving community-based or workplace hypertension programmes may overcome some barriers to optimal care.

Exploring biomarkers associated with deteriorating vascular health using a targeted proteomics chip: The SABPA study

In this observational study, by the use of a multiplex proteomic platform, we aimed to explore associations between 92 targeted proteins involved in cardiovascular disease and/or inflammation, and phenotypes of deteriorating vascular health, with regards to ethnicity.Proteomic profiling (92 proteins) was carried out in 362 participants from the Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study of black and white African school teachers (mean age 44.7 ± 9.9 years, 51.9% women, 44.5% Black Africans, 9.9% with known cardiovascular disease). Three proteins with <15% of samples below detectable limits were excluded from analyses. Associations between multiple proteins and prevalence of hypertension as well as vascular health [Carotid intima-media thickness (cIMT) and pulse wave velocity (PWV)] measures were explored using Bonferroni-corrected regression models.Bonferroni-corrected significant associations between 89 proteins and vascular health markers were further adjusted for clinically relevant co-variates. Hypertension was associated with growth differentiation factor 15 (GDF-15) and C-X-C motif chemokine 16 (CXCL16). cIMT was associated with carboxypeptidase A1 (CPA1), C-C motif chemokine 15 (CCL15), chitinase-3-like protein 1 (CHI3L1), scavenger receptor cysteine-rich type 1 protein M130 (CD163) and osteoprotegerin, whereas PWV was associated with GDF15, E-selectin, CPA1, fatty acid-binding protein 4 (FABP4), CXCL16, carboxypeptidase B (CPB1), and tissue-type plasminogen activator. Upon entering ethnicity into the models, the associations between PWV and CPA1, CPB1, GDF-15, FABP4, CXCL16, and between cIMT and CCL-15, remained significant.Using a multiplex proteomic approach, we linked phenotypes of vascular health with several proteins. Novel associations were found between hypertension, PWV or cIMT and proteins linked to inflammatory response, chemotaxis, coagulation or proteolysis. Further, we could reveal whether the associations were ethnicity-dependent or not.

Monocyte Chemoattractant Protein-1 and Large Artery Structure and Function in Young Individuals: The African-PREDICT Study

To better understand hypertension development, the authors determined whether monocyte chemoattractant protein-1 (MCP-1) is associated with arterial stiffness (pulse wave velocity [PWV]) and carotid intima-media wall thickness (cIMT) in a young apparently healthy black and white population (N=403, aged 20-30 years). Carotid-femoral PWV, central systolic blood pressure, and cIMT were measured, and MCP-1, reactive oxygen species, inflammatory markers (interleukin 6, tumor necrosis factor α), and endothelial activation (intercellular adhesion molecule, vascular cell adhesion molecule) were determined from blood samples. Although carotid-femoral PWV and cIMT were similar between blacks and whites, black men and women showed higher central systolic blood pressure, MCP-1, and reactive oxygen species than whites (all P<.05). In addition, black women had higher brachial blood pressure and interleukin 6 (all P<.001). A consistent positive association only in black women between cIMT and MCP-1 in multiple regression analyses was found (R²=0.151, β=0.248; P=.021). In this model, cIMT was also independently associated with vascular cell adhesion molecule (β=0.251; P=.022). The authors found elevated central systolic blood pressure and MCP-1 in young blacks, where cIMT was independently associated with MCP-1 in black women.

Compliance or non-compliance of hypertensive adults to hypertension management at three primary healthcare day clinics in Tshwane

The objective of this article was to report on the rate of compliance to medication, sodium use and appointment keeping of hypertensive adults who are attending primary healthcare clinics in Tshwane. Despite the availability of effective management of hypertension globally, non-compliance to management still exists. This article reports on the hypertensive adult’s compliance to medication, sodium use and appointment keeping. The design was a cross-sectional descriptive study. The sample was n=101 hypertensive patients from three primary healthcare clinics. Structured interviews were used to gather the data. The results indicated a variation in compliance rate depending on the question asked. When investigating whether the participants received enough medication on their last visit to the clinic, 98% said that they received enough medication to last them a month (Nkosi 2008:130). However, the appointment-keeping scale revealed that 23% of the participants reported that they left the clinic without prescribed medication or missed an appointment. When, using the Hill-Bone Compliance Scale, individuals were asked a question using the verb forgetting, 9 out of 10 would answer ‘no’, but when the verb decide was used to determine compliance, 6 out of 10 would admit to deciding not to take their medication sometimes. In terms of sodium use, 33% showed good compliance and 44% low compliance (Nkosi 2008:138). Compliance with regard to taking hypertension medication was 70%, which is good. This study recommends that compliance to hypertension management be assessed by asking questions specifically for sodium use, medication and appointment keeping as it was clear from the findings of this study that a person would comply with appointment keeping but not take medication daily as prescribed or not use sodium as recommended.

Geographic differences in the associations between impaired glucose regulation and cardiovascular risk factors among young adults

AIMS

To assess geographic differences in the association between BMI, blood pressure and lipid levels with impaired glucose regulation among young adults from various geographical regions.

METHODS

This was a cross-sectional study including data from 6987 participants aged ≤ 30 years from India, Singapore, Australia, Greenland, Kenya and Tanzania. Impaired glucose regulation was determined by the 75-g oral glucose tolerance test. For each geographical region, BMI, blood pressure and lipids were examined and compared between participants with normal glucose tolerance and those with impaired glucose regulation. Multiple logistic regression models were used to assess the association between risk factors and impaired glucose regulation.

RESULTS

Indian and East African people had a higher prevalence of impaired glucose regulation compared with participants from other regions, despite their lower BMI. Compared with the other regions, blood pressure was lower among Indian and Singaporean people but higher in those from Greenland. Greenlanders had the highest, while Indian and East-African people, had the lowest level of HDL cholesterol. BMI was positively associated with impaired glucose regulation in all regions, and there were no statistically significant geographic differences. In the Indian, Singaporean and Australian participants, there was a positive association between blood pressure and impaired glucose regulation. Triglycerides were positively associated with and HDL cholesterol had no association with impaired glucose regulation in all geographical regions.

CONCLUSIONS

Higher BMI and triglyceride levels were positively associated with prevalent impaired glucose regulation in all geographical regions. There were geographic differences in the association between impaired glucose regulation and blood pressure and lipids, probably reflecting environmental and genetic factors.

Frequency, Awareness, Treatment and Control of Hypertension in the over 40 Population of Erzincan

To determine distribution of blood pressure (BP) and prevalence, awareness, treatment and control of hypertension in 5 primary health care centers of Erzincan. A population-based cross-sectional survey was carried out in January - May 2009. A two-stage sampling method was used to select a sample of adult population 40 and over years of age. The total number of participants was 1570. Data were collected by face-to-face interview technique in the primary health care setting. Main outcome measures; mean systolic and diastolic blood pressures, distribution of blood pressure, prevalence of hypertension (mean systolic BP≥140 mmHg or mean diastolic BP ≥90 mmHg, or previously diagnosed and/or taking antihypertensive drugs) awareness, treatment and control of hypertension were assessed. The overall hypertension prevalence was 67.0% in the study sample and 77.4% of them were aware of their hypertension and received a pharmacologic treatment. Of the patients who were aware of the disease, 51.8% use drug treatment. Of the patients who had a drug treatment, 33.9 % were under control in terms of blood pressure. Our data indicate that hypertension is a highly prevalent but inadequately managed health problem in Erzincan. There is an urgent need for population-based strategies to improve prevention, early detection, and control of hypertension.

A high burden of hypertension in the urban black population of Cape Town: the cardiovascular risk in Black South Africans (CRIBSA) study

OBJECTIVE

To determine the prevalence, associations and management of hypertension in the 25-74-year-old urban black population of Cape Town and examine the change between 1990 and 2008/09 in 25-64-year-olds.

METHODS

In 2008/09, a representative cross-sectional sample, stratified for age and sex, was randomly selected from the same townships sampled in 1990. Cardiovascular disease risk factors were determined by administered questionnaires, clinical measurements and fasting biochemical analyses. Logistic regression models evaluated the associations with hypertension.

RESULTS

There were 1099 participants, 392 men and 707 women (response rate 86%) in 2008/09. Age-standardised hypertension prevalence was 38.9% (95% confidence interval (CI): 35.6-42.3) with similar rates in men and women. Among 25-64-year-olds, hypertension prevalence was significantly higher in 2008/09 (35.6%, 95% CI: 32.3-39.0) than in 1990 (21.6%, 95% CI: 18.6-24.9). In 2008/09, hypertension odds increased with older age, family history of hypertension, higher body mass index, problematic alcohol intake, physical inactivity and urbanisation. Among hypertensive participants, significantly more women than men were detected (69.5% vs. 32.7%), treated (55.7% vs. 21.9%) and controlled (32.4% vs. 10.4%) in 2008/09. There were minimal changes from 1990 except for improved control in 25-64-year-old women (1990∶14.1% vs. 2008/09∶31.5%).

CONCLUSIONS

The high and rising hypertension burden in this population, its association with modifiable risk factors and the sub-optimal care provided highlight the urgent need to prioritise hypertension management. Innovative solutions with efficient and cost-effective healthcare delivery as well as population-based strategies are required.

Association between γ-glutamyltransferase and prehypertension

Researchers have identified an association between baseline γ-glutamyltransferase (GGT) and prehypertension. However, data from China are limited. A cross-sectional study was performed among 2,205 subjects from Heilongjiang Province in China. Multiple logistic regression analyses revealed a significant association between baseline GGT and prehypertension [1.59, 95% confidence interval (CI), 1.18–2.16], comparing quartile 4 to quartile 1. Subgroup analyses showed a stronger association between GGT and prehypertension in Koreans; men, current alcohol drinkers and subjects with pre-diabetes. Receiver operating characteristics (ROC) analysis demonstrated that when GGT was higher than 20 U/l, the risk of developing prehypertension increased. Serum GGT is used as a biochemical liver test, but our findings suggest that baseline values may also predict prehypertension in Chinese.

Smoking and vascular dysfunction in Africans and Caucasians from South Africa

Background

Smoking is an important modifiable risk factor for cardiovascular disease, with limited research having been done in Africans. We aimed to determine the association between smoking and measurements of vascular function in Africans and Caucasians.

Methods

We determined anthropometric and cardiovascular variables, serum cotinine and C-reactive protein (CRP) in African and Caucasian participants from South Africa (n = 630).

Results

Africans had significantly lower body mass index (BMI), higher blood pressure and lower socio-economic status (SES) than Caucasians. Only African smokers showed increased arterial stiffness and a significant correlation between smoking and arterial stiffness. African smokers had increased and Caucasian smokers decreased high-density lipoprotein cholesterol (HDL-C) than the non-smokers. After adjusting for confounders, smoking showed few correlations, mainly with heart rate and CRP. In Africans, smoking also correlated positively with HDL-C, with the opposite result in Caucasians.

Conclusion

African smokers had significantly increased arterial stiffness, which was not found in Caucasian smokers. Africans generally demonstrated more associations between smoking and cardiovascular dysfunction than Caucasians.

Should obesity be blamed for the high prevalence rates of hypertension in black South African women?

Hypertension is highly prevalent in South Africa, resulting in high stroke mortality rates. Since obesity is very common among South African women, it is likely that obesity contributes to the hypertension prevalence. The aims were to determine whether black African women have higher blood pressures (BPs) than Caucasian women, and whether obesity is related to their cardiovascular risk. African (N=102) and Caucasian (N=115) women, matched for age and body mass index, were included. Correlations between obesity (total body fat, abdominal obesity and peripheral fat) and cardiovascular risk markers (haemodynamic parameters, lipids, inflammatory markers, prothrombotic factors, adipokines, HOMA-IR (homoeostasis model assessment insulin resistance)) were compared between the ethnic groups (adjusted for age, smoking, alcohol and physical activity). Comparisons between low- and high-BP groups were also made for each ethnic group. Results showed that African women had higher BP (P<0.01) with increased peripheral vascular resistance. Surprisingly, African women showed significantly weaker correlations between obesity measures and cardiovascular risk markers when compared to Caucasian women (specifically systolic BP, arterial resistance, cardiac output, fibrinogen, plasminogen activator inhibitor-1, leptin and resistin). Interestingly, the latter risk markers were also not significantly different between low- and high-BP African groups. African women, however, presented significant correlations of obesity with triglycerides, C-reactive protein and HOMA that were comparable to the Caucasian women. Although urban African women have higher BP than Caucasians, their obesity levels are weakly related to traditional cardiovascular risk factors compared to Caucasian women. The results, however, suggest a link with the development of insulin resistance.

Defining the metabolic syndrome in children and adolescents: will the real definition please stand up?

OBJECTIVES

To review the use of definitions of the metabolic syndrome in studies of children and adolescents and to review results from studies that used factor analysis to examine structure among cardiometabolic variables.

STUDY DESIGN

Literature review.

RESULTS

In 27 publications, authors used 40 unique definitions of the metabolic syndrome. Most of these definitions were adaptations of the adult definition developed by the National Cholesterol Education Program. In 11 studies that used exploratory factor analysis, the number of components ranged from 5 to 19, and the number of factors identified ranged from 1 to 5.

CONCLUSIONS

The use of multiple definitions of the metabolic syndrome argues strongly for the development of a standard pediatric definition.

The Prevalence of Metabolic Syndrome in Various Populations

The insulin resistance/metabolic syndrome is characterized by the variable co-existence of hyperinsulinemia, obesity, dyslipidemia (small dense low-density lipoprotein, hypertriglyceridemia, and decreased high-density lipoprotein cholesterol), and hypertension. The pathogenesis of the syndrome has multiple origins. However, obesity and sedentary lifestyle coupled with diet and still largely unknown genetic factors clearly interact to produce the syndrome. This multifactorial and complex trait of metabolic syndrome leads to increased risk of cardiovascular disease. The scope of this review is to examine the differences in prevalence of the metabolic syndrome in various groups (eg, according to age, sex, ethnicity, social status, or presence of obesity) that could help with the better understanding of the pathogenesis of this syndrome. This review also considers the impact of metabolic syndrome on cardiovascular disease.

Is there a single underlying factor for the metabolic syndrome in adolescents? A confirmatory factor analysis

OBJECTIVE

The lack of a universally applicable model for the metabolic syndrome in the pediatric population makes it difficult to define this syndrome and compare its prevalence across studies and diverse populations. We sought to assess whether a single underlying factor could represent the metabolic syndrome in adolescents.

RESEARCH DESIGN AND METHODS

Using data from the National Health and Nutrition Examination Survey (1999-2002), we conducted a confirmatory factor analysis to assess the validity of waist circumference, triglycerides, fasting insulin, and systolic blood pressure (SBP) as potential phenotypic traits for the metabolic syndrome in adolescents aged 12-17 years (n = 1,262). A multiple-group approach was used to test the invariance in factor loadings across sex and race/ethnicity.

RESULTS

The estimates of factor loadings for the total sample were 0.76, 0.46, 0.81, and 0.42 for waist circumference, triglycerides, fasting insulin, and SBP, respectively. The goodness-of-fit indexes were adequate for the total sample (comparative fit index, 0.99; standardized root mean square residual, 0.02), Caucasian boys (1.0; 0.01), African-American boys (0.99; 0.03), Mexican-American boys (1.0; 0.01), Mexican-American girls (1.0; 0.01), and Caucasian girls (0.95; 0.04) and acceptable for African-American girls (0.94; 0.05). There were no significant differences in factor loadings of the four measured variables between boys and girls and among the three racial or ethnic subgroups.

CONCLUSIONS

The metabolic syndrome as a single underlying factor for the four simple phenotypic traits may be plausible in adolescents. The proposed model appears to be generalizable across sex and race/ethnicity.

Obesity in South Africa

South Africa has not been spared in the rampant global increase in obesity. Throughout Africa, as elsewhere, ethnicity has a major impact on the incidence and pathogenesis of comorbid diseases, particularly diabetes. Combined figures for obesity and overweight (body mass index [BMI] > 25 kg m(-2)) obtained across all ethnic groups in the adult population in 1998, were 57% for women and 29% for men. From the 1960s until the late 1980s, the notion of 'healthy' or 'benign' obesity was propagated in South Africa. Not surprisingly, this led to ignorance around the problem of obesity, and treatment of some of the comorbid diseases was neglected. Fortunately, as an increasing number of seminal studies draw us closer to reality, the misperception of benign obesity is being corrected. This is allowing us to address the real issues underlying the current epidemic, and to recognize and manage the comorbid diseases, in particular type 2 diabetes. A new framework for research is also emerging as we begin to define the factors underlying the impact of ethnicity on obesity.

Association between nocturnal vagal tone and sleep depth, sleep quality, and fatigue in alcohol dependence

BACKGROUND

This study examined whether nocturnal vagal tone as indexed by the high-frequency (HF) power component of heart rate variability is related to measures of sleep depth and daytime perceptions of sleep quality, sleepiness, and fatigue in alcohol dependence.

METHODS

Abstinent alcohol-dependent patients (n = 14) and comparison control subjects (n = 14) underwent all-night polysomnography along with assessment of heart rate variability during an awake period before sleep and during sleep. Sleep-quality perceptions, along with self-reported sleepiness and levels of energy and fatigue, were obtained in the morning.

RESULTS

As compared with control subjects, alcohol-dependent persons showed marked decreases in delta sleep along with impairments of sleep quality and daytime energy. In addition, alcoholics showed a decrease of the HF power component of heart rate variability during the awake period before sleep and during nocturnal sleep as compared with control subjects. HF power during the awake period before sleep correlated with electroencephalographic delta sleep and delta power observed during the subsequent sleep period. HF power during the awake period before sleep also correlated with morning reports of sleep quality, sleepiness, and fatigue.

CONCLUSIONS

Alcohol dependence compromises vagal output measured before sleep onset, which correlates with loss of delta sleep and with morning reports of sleep impairments. Testing of interventions that target sympathovagal balance might identify new strategies for partial amelioration of the sleep disturbances and impairments in daytime functioning observed in persons with alcohol dependence.

An evaluation of the metabolic syndrome in a large multi-ethnic study: the Family Blood Pressure Program

BACKGROUND

The Family Blood Pressure Program is an ongoing, NHLBI-sponsored, multi-center program to study the genetic determinants of high blood pressure. The goal of this particular study was to study patterns of metabolic syndrome (MetS) in four ethnic groups: African Americans, Caucasians, Hispanics, and Asians.

METHODS

A major part of participants in three networks GENOA, HyperGEN and SAPPHIRe were recruited mainly through hypertensive probands. MetS was defined as a categorical trait following the National Cholesterol Education Program definition (c-MetS). MetS was also characterized quantitatively through multivariate factor analyses (FA) of 10 risk variables (q-MetS). Logistic regression and frequency tables were used for studying associations among traits.

RESULTS

Using the NCEP definition, the Hispanic sample, which by design was enriched for type 2 diabetes (T2D), had a very high prevalence of MetS (73%). In contrast, its prevalence in Chinese was the lowest (17%). In African Americans and Hispanics, c-MetS was more prevalent in women than in men. Association of c-MetS with type 2 diabetes (T2D) was prominent in the Hispanics and African Americans, less pronounced in the Whites and Japanese, (although still significant), and weakest in the Chinese sample. Using FA without rotation, we found that the main factor loaded obesity (OBS) and blood pressure (BP) in African Americans; OBS and insulin (INS) in Hispanics, in Japanese, and in Whites; and OBS alone in Chinese. In Hispanics, Whites, and Japanese, BP loaded as a separate factor. Lipids in combination with INS also loaded in a separate factor. Using FA with Varimax rotation, 4 independent factors were identified: "Obesity-INS," "Blood pressure," "Lipids-INS," and "Central obesity." They explained about 60% of the variance present in the original risk variables.

CONCLUSION

MetS ethnic differences were identified. Ascertaining for hypertension or T2D increased the MetS prevalence in networks compared with the one in the US general population. Obesity was the most prominent risk factor contributing to both c-MetS and q-MetS. INS contributed in two important factors (obesity and lipids). The information imbedded into c-MetS trait /q-MetS factors scores can contribute in future research of the MetS, especially its utilization in the genetic analysis.