Individual and area-level socioeconomic correlates of hypertension prevalence, awareness, treatment, and control in uMgungundlovu, KwaZulu-Natal, South Africa

BACKGROUND

Hypertension is the second leading risk factor for death in South Africa, and rates have steadily increased since the end of Apartheid. Research on the determinants of hypertension in South Africa has received considerable attention due to South Africa's rapid urbanization and epidemiological transition. However, scant work has been conducted to investigate how various segments of the Black South African population experience this transition. Identifying the correlates of hypertension in this population is critical to the development of policies and targeted interventions to strengthen equitable public health efforts.

METHODS

This analysis explores the relationship between individual and area-level socioeconomic status and hypertension prevalence, awareness, treatment, and control within a sample of 7,303 Black South Africans in three municipalities of the uMgungundlovu district in KwaZulu-Natal province: the Msunduzi, uMshwathi, and Mkhambathini. Cross-sectional data were collected on participants from February 2017 to February 2018. Individual-level socioeconomic status was measured by employment status and educational attainment. Ward-level area deprivation was operationalized by the most recent (2011 and 2001) South African Multidimensional Poverty Index scores. Covariates included age, sex, BMI, and diabetes diagnosis.

RESULTS

The prevalence of hypertension in the sample was 44.4% (n = 3,240). Of those, 2,324 were aware of their diagnosis, 1,928 were receiving treatment, and 1,051 had their hypertension controlled. Educational attainment was negatively associated with hypertension prevalence and positively associated with its control. Employment status was negatively associated with hypertension control. Black South Africans living in more deprived wards had higher odds of being hypertensive and lower odds of having their hypertension controlled. Those residing in wards that became more deprived from 2001 to 2011 had higher odds of being aware of their hypertension, yet lower odds of receiving treatment for it.

CONCLUSIONS

Results from this study can assist policymakers and practitioners in identifying groups within the Black South African population that should be prioritized for public health interventions. Black South Africans who have and continue to face barriers to care, including those with low educational attainment or living in deprived wards had worse hypertension outcomes. Potential interventions include community-based programs that deliver medication to households, workplaces, or community centers.

Prevalence of cardio-metabolic multi-morbidity and associated risk factors in a population-based sample of South Africans

Objectives

Cardio-metabolic multi-morbidity (CM), the co-existence of two or more cardio-metabolic disorders in the same person, is rapidly increasing. We examined the prevalence and risk factors associated with CM in a population-based sample of South African adults.

Study design

Data were analyzed on individuals aged ≥15 years from the South African National Health and Nutrition Examination Survey (SANHANES), a cross sectional population-based survey conducted in 2011-2012.

Methods

CM was defined as having ≥2 of hypertension, diabetes, stroke and angina. Multivariable logistic regression was used to investigate the sociodemographic and modifiable risk factors associated with CM.

Results

Of the 3832 individuals analyzed, the mean age was 40.8 years (S.D. 18.3), 64.5% were female and 18% were ≥60 years. The prevalence of CM was 10.5%. The most prevalent CM cluster was hypertension and diabetes (7.3%), followed by hypertension and angina (2.6%) and hypertension and stroke (1.9%). Of the individuals with diabetes, nearly three quarters had multi-morbidity from co-occurring hypertension, angina and/or stroke and of those with hypertension, 30% had co-occurring diabetes, angina and/or stroke. Age (30-44 years Adjusted Odds Ratio (AOR) = 2.68, 95% CI: 1.15-6.26), 45-59 years AOR = 16.32 (7.38-36.06), 60-74 years AOR = 40.14 (17.86-90.19), and ≥75 years AOR = 49.54 (19.25-127.50) compared with 15-29 years); Indian ethnicity (AOR = 2.58 (1.1-6.04) compared with black African ethnicity), overweight (AOR = 2.73 (1.84-4.07)) and obesity (AOR = 4.20 (2.75-6.40)) compared with normal or underweight) were associated with increased odds of CM.

Conclusions

A tenth of South Africans have two or more cardio-metabolic conditions. The findings call for immediate prioritization of prevention, screening and management of cardio-metabolic conditions and their risk factors to avert large scale health care costs and adverse health outcomes associated with multi-morbidity.

Beta-blockers for hypertension

BACKGROUND

Two recent systematic reviews found first-line beta-blockers to be less effective in reducing the incidence of stroke and the combined endpoint of stroke, myocardial infarction, and death compared to all other antihypertensive drugs taken together. However, beta-blockers might be better or worse than a specific class of drugs for a particular outcome measure so that comparing beta-blockers with all other classes taken together could be misleading. In addition, these systematic reviews did not assess the tolerability of beta-blockers relative to other antihypertensive medications. We thus undertook this review to re-assess the place of beta-blockade as first-line therapy for hypertension relative to each of the other major classes of antihypertensive drugs.

OBJECTIVES

To quantify the effectiveness and safety of beta-blockers on morbidity and mortality endpoints in adults with hypertension.

SEARCH STRATEGY

We searched eligible studies up to June 2006 in the Cochrane Controlled Trials Register, Medline, Embase, and reference lists of previous reviews, and by contacting hypertension experts.

SELECTION CRITERIA

We selected randomised controlled trials which assessed the effectiveness of beta-blockers compared to placebo, no therapy or other drug classes, as monotherapy or first-line therapy for hypertension, on mortality and morbidity endpoints in men and non-pregnant women aged 18 years or older.

DATA COLLECTION AND ANALYSIS

At least two authors independently applied study selection criteria, assessed study quality, and extracted data; with differences resolved by consensus. We expressed study results as relative risks (RR) with 95% confidence intervals (CI) and conducted quantitative analyses with trial participants in groups to which they were randomly allocated, regardless of which or how much treatment they actually received. In the absence of significant heterogeneity between studies (p>0.1), we performed meta-analysis using a fixed effects method. Otherwise, we used the random effects method and investigated the cause of heterogeneity by stratified analysis. In addition, we used the Higgins statistic (I(2)) to quantify the amount of between-study variability in effect attributable to true heterogeneity rather than chance.

MAIN RESULTS

Thirteen randomised controlled trials (N=91,561 participants), which met our inclusion criteria, compared beta-blockers to placebo or no treatment (4 trials with 23,613 participants), diuretics (5 trials with 18,241 participants), calcium-channel blockers (CCBs: 4 trials with 44,825 participants), and renin-angiotensin system (RAS) inhibitors (3 trials with 10,828 participants). The risk of all-cause mortality was not different between first-line beta-blockers and placebo (RR 0.99, 95%CI 0.88 to 1.11, I(2)=0%), diuretics or RAS inhibitors, but was higher for beta-blockers compared to CCBs (RR 1.07, 95%CI 1.00 to 1.14, I(2)=2.2%; ARI=0.5%, NNH=200). The risk of total cardiovascular disease (CVD) was lower for first-line beta-blockers compared to placebo (RR 0.88, 95%CI 0.79 to 0.97, I(2)=21.4%, ARR=0.7%, NNT=140). This is primarily a reflection of the significant decrease in stroke (RR 0.80, 95%CI 0.66 to 0.96; I(2)=0%; ARR=0.5%, NNT=200); coronary heart disease (CHD) risk was not significantly different between beta-blockers and placebo. The effect of beta-blockers on CVD was significantly worse than that of CCBs (RR 1.18, 95%CI 1.08 to 1.29, I(2)=0%; ARI=1.3%, NNH=80), but was not significantly different from that of diuretics or RAS inhibitors. Increased total CVD was due to an increase in stroke compared to CCBs (RR 1.24, 95%CI 1.11 to 1.40, I(2)=0%; ARI=0.6%, NNH=180). There was also an increase in stroke with beta-blockers as compared to RAS inhibitors (RR 1.30, 95%CI 1.11 to 1.53, I(2)=29.1%; ARI=1.5%, NNH=65). CHD was not significantly different between beta-blockers and diuretics or CCBs or RAS inhibitors. In addition, patients on beta-blockers were more likely to discontinue treatment due to side effects than those on diuretics (RR 1.86, 95%CI 1.39 to 2.50, I(2)=78.2%, ARI=6.4% NNH=16) and RAS inhibitors (RR 1.41, 95%CI 1.29 to 1.54, I(2)=12.1%; ARI=5.5%, NNH=18), but there was no significant difference with CCBs.

AUTHORS' CONCLUSIONS

The available evidence does not support the use of beta-blockers as first-line drugs in the treatment of hypertension. This conclusion is based on the relatively weak effect of beta-blockers to reduce stroke and the absence of an effect on coronary heart disease when compared to placebo or no treatment. More importantly, it is based on the trend towards worse outcomes in comparison with calcium-channel blockers, renin-angiotensin system inhibitors, and thiazide diuretics. Most of the evidence for these conclusions comes from trials where atenolol was the beta-blocker used (75% of beta-blocker participants in this review). However, it is not known at present whether beta-blockers have differential effects on younger and elderly patients or whether there are differences between the different sub-types of beta-blockers.

Coronary artery disease and risk factors in Black South Africans--a comparative study

OBJECTIVE

The purpose of this study was to identify and compare coronary risk factors in different South African ethnic groups with angiographically documented significant coronary artery disease (CAD).

DESIGN

An observational retrospective analysis.

METHODS

Hospital records of 500 consecutive patients with no previous coronary interventions who underwent coronary angiography at Chris Hani Baragwanath Hospital, Soweto over a 2-year period were reviewed. Patients with significant CAD were selected for this study. Data analyzed included demographics, presenting diagnoses, coronary risk factors, number of coronary arteries significantly affected and extent of CAD, left ventricular ejection fraction (LVEF), and the main treatment modality for CAD.

RESULTS

Of the 206 patients with significant CAD, 85 were Africans and 121 were non-Africans. There were significantly more females in the African group (31% vs 12%, P=.0023) and hypertension was more prevalent in the same group (78% vs 55%, P=.0006). Serum total (TC) and low-density lipoprotein (LDL) cholesterol were significantly lower in African than in non-African patients [189.5 (96.67-313.2) vs 228.2 (127.6-464) mg/dL; P=.0006 and 100.5 (34.8-282.3) vs 146.9 (42.54-313.2) mg/dL; P=.0001, respectively].

CONCLUSION

Cholesterol levels in this group of African patients with angiographically significant CAD are within the target range recommended by the adult treatment panel III (ATP III) guidelines of the National Cholesterol Education Program (NCEP). These data have implications for risk assessment using cholesterol and the role of cholesterol lowering treatment in populations of developing countries.

A prospective study of serum lipoproteins after coronary artery bypass surgery

We examined the acute and long-term effects of coronary artery bypass (CABG) surgery on serum lipid, lipoprotein and apolipoprotein levels. One series of 34 patients having CABG surgery was studied pre-operatively and for six weeks afterwards, and another 22 patients were investigated before and two years after CABG surgery. None of the patients studied received any lipid-lowering drug therapy or specific dietary advice. In both groups, pre-operative serum lipoprotein (a) (Lp(a)) and serum triglyceride concentrations were raised and serum high-density lipoprotein (HDL) cholesterol and apolipoprotein AI (apo AI) were low compared to healthy people. Acutely, there were profound decreases of 40-60% in the serum levels of cholesterol (p < 0.001), low-density lipoprotein cholesterol (p < 0.05), triglycerides (p < 0.01), Lp(a) (p < 0.05) and apolipoprotein B (apo B) (p < 0.05). There was a small decrease in serum apo A1 (p < 0.05), and serum HDL cholesterol showed no change. All these variables regained their pre-operative values within six weeks. Two years postoperatively, serum Lpa was 40% less than its pre-operative concentration (p < 0.001) and HDL cholesterol had increased (p < 0.001). Triglyceride levels decreased (p < 0.02) when beta-blockade was withdrawn. The long-term decrease in Lp(a) following surgery is unlikely to be due either to stopping beta-blockers or to life-style changes. Myocardial ischaemia relieved by the operation may have been partially responsible for its previously raised concentration.

A cross-sectional evaluation of cardiovascular risk factors in coronary heart disease associated with type 1 (insulin-dependent) diabetes mellitus

The contribution from lipoproteins, blood pressure, albuminuria and demographic variables to coronary heart disease in 90 adult subjects with and 172 without Type 1 diabetes mellitus was examined in order to investigate whether risk factors were of equivalent importance in diabetic and non-diabetic coronary heart disease. Coronary heart disease (CHD) was present in roughly 25% of subjects in each group. In Type 1 diabetes those with CHD had significantly higher levels of systolic blood pressure, albumin excretion, serum creatinine, triglycerides, VLDL cholesterol and C-peptide, and reductions in serum concentrations of HDL and HDL2 cholesterol, in comparison to those without. However, the prevalence of smokers, and concentrations of Lp(a), ApoB and fibrinogen were comparable. Blood pressure and HDL cholesterol were higher in the CHD group with Type 1 diabetes in comparison to the nondiabetic group with CHD, although LDL concentrations and the prevalence of Lp(a) concentrations > 200 mg/l were lower. Logistic regression analysis revealed the strongest independent predictors of CHD in Type 1 diabetes were serum triglycerides, systolic blood pressure, age, serum LDL cholesterol, and the daily insulin dosage, whereas in the non-diabetic control group HDL2 cholesterol, Lp(a), ApoA1 and ApoB, total serum cholesterol and body mass index were additional predictors. CHD in Type 1 diabetes appears to be most closely associated with increasing age and levels of blood pressure and total serum lipids. Apolipoproteins and albuminuria did not seem to be important independent predictors of CHD in Type 1 diabetes, whereas the former were more clearly associated with CHD in non-diabetic controls.

Rapid screening for specific mutations in patients with a clinical diagnosis of familial hypercholesterolaemia

We describe a rapid screening procedure to identify known DNA sequence changes in individuals diagnosed as having heterozygous familial hypercholesterolaemia (FH). The screening is made possible by combining a rapid DNA extraction protocol and small scale polymerase chain reaction DNA amplification, followed by oligonucleotide melting or restriction enzyme digestion. We have screened for two different mutations; firstly a mutation in the apolipoprotein B (apo B) gene that results in the substitution of glutamine (Gln) for arginine (Arg) at amino acid residue 3500 (apo B3500 mutation). Apo B is the principal component of the protein moiety of low density lipoprotein (LDL) and the mutation reduces the affinity for the LDL receptor (LDL-R). Secondly we have screened for a point mutation in the LDL-R gene itself that creates a new Pst I restriction enzyme site. This mutation in the LDL-R gene (LDL-R664 mutation) results in the substitution of leucine (Leu) for proline (Pro) at amino acid 664 and is known to slow processing of the LDL-R precursor to the mature form and to reduce the affinity of the receptor on the cell surface for LDL. In 77 unrelated patients with a clinical diagnosis of FH two out of 77 (2.6%) were positive for the apo B3500 mutation. Three (3.9%) were positive for the LDL-R664 mutation. Thus these two mutations might account for 5-6% of patients in the U.K. with a clinical diagnosis of FH (5000-6000 people).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum lipoprotein(a) in patients heterozygous for familial hypercholesterolemia, their relatives, and unrelated control populations

Serum lipoprotein(a) (Lp[a]) levels were significantly higher in 89 patients with heterozygous familial hypercholesterolemia (FH) (geometric mean, 22.7 mg/dl) than in 109 normocholesterolemic controls (10.0 mg/dl, p less than 0.05) and 40 controls (9.1 mg/dl, p less than 0.05) with similarly elevated low density lipoprotein cholesterol levels due to other primary hypercholesterolemias. To provide further evidence that the increased serum Lp(a) concentration was due to inheritance of the FH gene, 24 unaffected first-degree relatives were compared with their FH probands. Serum Lp(a) in affected individuals was significantly greater than in unaffected relatives (geometric means, 26.5 versus 13.7 mg/dl, respectively; p less than 0.05). Family membership exerted an effect on serum Lp(a) concentrations, indicating that other genetic influences were also operating, as is known to be the case in general populations. Serum Lp(a) in 30 of the FH patients, who had coronary heart disease, was not significantly different from 30 age- and sex-matched controls with FH but with coronary heart disease (geometric means, 23.6 versus 24.7 mg/dl, respectively). FH is associated with an increase in serum Lp(a). Elevated serum Lp(a) concentrations should probably now be regarded as a component of the clinical syndrome of FH. However, within our FH population Lp(a) did not distinguish those with clinically overt coronary heart disease from those without the disease.