**5.4 Hypertension**

Hypertension (blood pressure ≥ 140/90 mm Hg) [64] is considered one of the most important risk factors for developing CVD [50, 78] due to organ injury to the heart and kidneys. [79] Sharp increases in childhood hypertension have been reported in SA recently. [11] In childhood, hypertension treatment does not reverse the target organ injury and although hypertension treatment will significantly reduce event rates, the burden of CVD event rates will remain high though adulthood. [79] SA has a high hypertension burden with 44% and 41% of adult (≥15 years) black African women and men respectively. [46] In our adult populations the urban women in Gauteng had lower prevalence of 36.4% compared to the peri-urban adults in the FS (53.2%). [39] The elderly in urban Gauteng had the highest prevalence (68.%). [57] (**Table 2**) This was consistent with the national prevalence (84% among both genders aged ≥65 years), indicating that

**51**

*Double Burden of Poverty and Cardiovascular Disease Risk among Low-Resource Communities…*

**Rural children Eastern Cape (n = 232) %**

Obese BMI:A ≥ 3 [74] 0.0 [24] 4.0 [25] 2.5 [29] 0.0 [32]

**Periurban children Free State (n = 98) %**

4.3 [24] 17.0 [25] 15.8 [29] 1.0 [32]

1.3 [24] 19.4 3.0 10.2 [32]

42.5 [24] 30.6 19.2 95.9 [32]

2.12 [24] 12.2 2.5 28.6 [32]

12.4 [24] 35.7 4.4 1.0 [32]

10.3[24] 6.5 6.9 —

7.6 — — —

4.6 — — —

**Peri-urban children Gauteng (n = 203) %**

**Urban children Gauteng (n = 152) %**

the hypertension burden increases with age. [46, 80] A recent national survey has found an overall prevalence of 43%, of which 58% were unaware of the condition and thus did not receive treatment. [80] Similar results were observed where only 36.8% of the hypertensive urban elderly in Gauteng used hypertensive medication.

Hyperhomocysteienaemia >15 umol/L [61] 1.6 — — — Fibrinogen >3.5 g/L [65] 14.8 — — — Inflammation (HS-CRP) ≥3 mg/dL [62] 19.0 [24] 7.8 — —

In summary, our results showed high levels of hypertension in adults and the elderly in both urban and peri-urban areas. A recent national survey has found older age, obesity and lower education levels as the main risk factors for hypertension in SA. [80] High prevalence of obesity and poor education levels have been

Diabetes mellitus is the most common, but also the most complex CDL. [81, 82] Hyperglycaemia affects multiple organs and can lead to arterial hypertension. [83] It is estimated that the cause of death in 80% of individuals suffering from type 2 diabetes will be due to thrombotic complications of which 75% will result from a cardiovascular event. [84] Data on the incident rates of children with diabetes are available for only 6% of African countries and may be due to lack of screening tests available in the poor and low income communities. [84] Results in **Tables 2** and **3** indicated that 38.5% urban elderly (Gauteng), [57] 16.0% peri-urban adults (FS), [39] 10.3% rural children

[43] No hypertension data were available for the children.

**5.5 Hyperglycaemia, diabetes and metabolic syndrome**

identified in all our adult communities.

*DOI: http://dx.doi.org/10.5772/intechopen.95992*

**values**

[74]

[75]

[75]

[75]

≥1.12 mmol/L (0–9 years old) ≥1.47 mmol/L (10–19 years old)[75]

>6.1 mmol/L [76]

[69]

[70]

**Variable Reference** 

Overweight BMI:A ≥ 2 < 3

High serum TC levels ≥5.18 mmol/L

Low HDL-C levels <1.04 mmol/L

High LDL-C levels ≤3.37 mmol/L

Serum vitamin B12 <156 pmol/L

Serum folate <5.9 nmol/dL

*Cardiovascular risk factors of children.*

Hypertriglyceridaemia (High TRG levels)

Hyperglycaemia (serum glucose)

**Table 3.**


*Double Burden of Poverty and Cardiovascular Disease Risk among Low-Resource Communities… DOI: http://dx.doi.org/10.5772/intechopen.95992*

#### **Table 3.**

*Lifestyle and Epidemiology - The Double Burden of Poverty and Cardiovascular Diseases...*

Overweight BMI ≥ 25 < 30 [60] 39.3 [37] 26.0 [44] 29.5 [57] Obese BMI ≥ 30 [60] 43.0 [37] 41.9 [44] 31.5 [57] High serum TC levels ≥6.2 mmol/L [61] 0.5 [37] 16.7 22.3 [57]

High LDL-C levels >4.1 mmol/L [60, 63] 0.5 [37] 16.7 14.6 [57]

Fibrinogen >3.5 g/L [65] — — 68.0 [57] Inflammation (HS-CRP) ≥3 mg/dL [62] — 56.9 68.3 [57]

Serum vitamin B6 <8.6 mcg/L [67] — — 98.0 [57] Serum vitamin B12 <156 pmol/L [68, 69] — — 4.8 [57] Serum folate <5.9 nmol/dL [70] — — 9.6 [57]

<1.3 mmol/L (adult women) [61, 62]

Hg (systolic/diastolic blood pressure) [64]

diastolic blood pressure) [64]

homocysteiene)

**women Gauteng (n = 628) %**

≥2.3 mmol/L [60, 63] 24.7 [37] 12.7 [39] 13.8 [57]

>5.5 mmol/L [66] — 16.0 [39] 38.5 [57]

**Peri-urban adults Free State (n = 271) %**

43.0 [37] 62.7 [39] 76.2 [57]

11.6 [37] 12.7 10.8 [57]

36.4 [37] 53.2 [39] 68.0 [57]

— — 66.4 [57]

**Urban elderly Gauteng (n = 170) %**

**Variable Reference values Urban** 

Low HDL-C levels <1 mmol/L (adult men)

High normal BP 130–139 mm Hg/85–89 mm

Hypertensive ≥140/≥90 mm Hg (systolic/

Hyperhomocysteienemia >15 umol/L [61](serum

*Cardiovascular risk factors in adults and elderly.*

Hypertriglyceridaemia (High TRG levels)

Hyperglycaemia (serum

glucose)

**Table 2.**

communities, the results highlight the increasing burden of overweight among children (**Table 3**). The high prevalence of overweight and obesity in our study communities is a concern as the comorbidities associated with overweight/obesity

Hypertension (blood pressure ≥ 140/90 mm Hg) [64] is considered one of the most important risk factors for developing CVD [50, 78] due to organ injury to the heart and kidneys. [79] Sharp increases in childhood hypertension have been reported in SA recently. [11] In childhood, hypertension treatment does not reverse the target organ injury and although hypertension treatment will significantly reduce event rates, the burden of CVD event rates will remain high though adulthood. [79] SA has a high hypertension burden with 44% and 41% of adult (≥15 years) black African women and men respectively. [46] In our adult populations the urban women in Gauteng had lower prevalence of 36.4% compared to the peri-urban adults in the FS (53.2%). [39] The elderly in urban Gauteng had the highest prevalence (68.%). [57] (**Table 2**) This was consistent with the national prevalence (84% among both genders aged ≥65 years), indicating that

have negative effects on health across the life cycle. [71]

**50**

**5.4 Hypertension**

*Cardiovascular risk factors of children.*

the hypertension burden increases with age. [46, 80] A recent national survey has found an overall prevalence of 43%, of which 58% were unaware of the condition and thus did not receive treatment. [80] Similar results were observed where only 36.8% of the hypertensive urban elderly in Gauteng used hypertensive medication. [43] No hypertension data were available for the children.

In summary, our results showed high levels of hypertension in adults and the elderly in both urban and peri-urban areas. A recent national survey has found older age, obesity and lower education levels as the main risk factors for hypertension in SA. [80] High prevalence of obesity and poor education levels have been identified in all our adult communities.

#### **5.5 Hyperglycaemia, diabetes and metabolic syndrome**

Diabetes mellitus is the most common, but also the most complex CDL. [81, 82] Hyperglycaemia affects multiple organs and can lead to arterial hypertension. [83] It is estimated that the cause of death in 80% of individuals suffering from type 2 diabetes will be due to thrombotic complications of which 75% will result from a cardiovascular event. [84] Data on the incident rates of children with diabetes are available for only 6% of African countries and may be due to lack of screening tests available in the poor and low income communities. [84] Results in **Tables 2** and **3** indicated that 38.5% urban elderly (Gauteng), [57] 16.0% peri-urban adults (FS), [39] 10.3% rural children

(EC), [24] 6.5% peri-urban children (FS), and 6.9% peri-urban children (Gauteng) had high serum glucose levels. An increased prevalence of diabetes was reported for developing countries, [85] and it can be concluded that the prevalence of hyperglycaemia in all age groups in urban, peri-urban and rural areas in SA is concerning.

#### **5.6 Haemostasis**

The development of coronary artery disease and myocardial infarction has both atheromatous and thrombotic components. Haemostasis is a finely balanced system of clot formation and fibrinolysis. [86–88] Fibrinogen is recognised as an independent risk marker of CVD. Fibrinogen, because of its mass, also has a direct effect on the blood viscosity and a physical functional effect on platelet aggregation. [65, 89] Studies have indicated an increased level of plasma fibrinogen in black South Africans. [12, 57, 90] An increase of one gram per litre in plasma fibrinogen doubles the risk of CVD. [89] The fibrinogen levels were measured in two of the communities. High fibrinogen levels were observed in 68.0% of the elderly [57] (**Table 2**) and 14.8% of the rural children (**Table 3**), indicating an increased risk for CVD.

### **5.7 Homocysteine metabolism**

#### *5.7.1 Homocysteine*

Several mechanisms have been proposed to clarify the link between homocysteine and pro-thrombotic state. The oxidative damage to the endothelium, combined with inhibition of the vasculo-protective function of nitric oxide, enhances thrombogenecity. [91] Homocysteine is metabolised by (a) the trans-sulphuration pathway which results in the production of cystathionine - a process that requires vitamin B6 and the main route of metabolism is via a methionine-conserving pathway - a process that requires methyltetrahydrofolate (from folic acid) and vitamin B12 as co-factor or alternatively (b) by the remethylation pathway taking place in the kidney and liver (where betaine is utilised instead of folate). [92–95] An association between elevated plasma homocysteine and the development of atherosclerosis has been confirmed. [96] Studies in animal models have shown that elevated homocysteine promoted atherosclerosis by increased oxidative stress impaired endothelial function and increased thrombogenecity. [92, 93, 95–99] Epidemiological retrospective and prospective clinical studies established homocysteine as a potent independent risk factor for atherothrombotic vascular disease. [91, 92, 100] Additionally, homocysteine increase superoxide (O2 —) levels resulting in increased oxidative stress, causing an inflammatory state and increased atherosclerosis and ischemia reperfusion. Oxidative stress in return inhibits the cobalamine metabolism and enhances the cycle. [101, 102] The frequency of hyperhomocysteienaemia as an independent risk factor for atherothrombotic vascular disease [91, 92, 100] was found in 66.4% and 1.6% of the urban elderly [57] and rural children respectively. Thus, although homocysteine measurement did not form part of the objectives in all our communities, prevalence of hyperhomocysteienaemia in the urban elderly (Gauteng) (**Table 2**) and the rural children (EC) (**Table 3**) is an additional confirmation of an increased risk for CVD in the low income South African population.

#### *5.7.2 Serum vitamin B6 levels*

Vitamin B6 acts as coenzyme in the irreversible trans-sulfuration of homocysteine to cysteine. Higher vitamin B6 level are associated with lower homocysteine levels. Fat metabolism requires carnitine, obtained either directly [103] through diet or via

**53**

**5.8 Inflammation**

*Double Burden of Poverty and Cardiovascular Disease Risk among Low-Resource Communities…*

synthesis requiring lysine and vitamin B6. Vitamin B6 deficiency was also found to be associated with decreased plasma PUFAs (n-6 and n-3) which may be associated with elevated cardiovascular risk and a contributing factor to the anti-inflammatory response. [104, 105] Low circulating vitamin B6 levels have been found inversely related to inflammatory markers (HS-CRP, fibrinogen, IL-6 and TNF-α) and are related to the incidence of inflammatory diseases (rheumatoid arthritis, CVD, and diabetes). [106, 107] Vitamin B6 levels were only available for the urban elderly and 98% of the respondents had low serum vitamin B6 levels (**Table 2**). Vitamin B6 levels were not available for any of the children, but pre-school children in Zambia indicated a suboptimal vitamin B6 in the studied group. [108] It would, therefore, be beneficial to include vitamin B6 serum levels in their analytical profile in future.

Low serum folate levels is a cardiovascular risk marker independently from homocysteine level. [109] Folate, as a donor of one-carbon units, is essential for methylation and affects numerous metabolisms involved in CVD [110] and accurate replication of deoxyribonucleic acid (DNA) and its repair. If DNA repair capacity of the cell is exceeded by the rate of damage to the genome, serious defects in cellular and tissue physiology occur, resulting in degenerative diseases including CVD. [111] The four mechanisms by which folate is involved in reducing atherosclerosis are: (1) Optimising methylation cycle and thereby directly reducing the homocysteine levels; (2) Acting directly as an antioxidant; (3) Interacting with enzyme endothelial nitric oxide synthase; (4) Affecting cofactor bioavailability of nitric oxide. Apart from being an independent cardiovascular risk marker, decreased serum folate levels also Indicate a decreased cell regeneration. [112] The serum folate levels were only available for two of the communities and 4.8% and 7.6% had low folate levels in the elderly [57] (**Table 2**) and rural children (EC) (**Table 3**) respectively. Study communities included in this study are therefore at risk for CVD and the general effect of ineffective cell recovery.

The cofactor cobalamin is required for the optimal function of the enzymes methionine synthase and L-methylmalonyl-CoA. [113, 114] During methionine synthase, homocysteine is converted to methionine, when the methyl group is transferred from 5-methylene tetrahydrofolate to cobalamin to form methylcobalamin and tetrahydrofolate while methylcobalamin donates its methyl group that binds to homocysteine to form methionin (required for the synthesis of S-adenosylmethionine [SAM]). [87, 115] SAM is required in many cellular methylation reactions, including the methylation ribonucleic acid (RNA) and DNA. [116, 117] Reduced synthesis of methionine as a result of insufficient cobalamine results in increased homocysteine levels. [104] Vitamin B12 is also the coenzyme required to remove the methyl group from folate, thereby activating folate. [117, 118] Serum vitamin B12 was only available for the elderly in Gauteng (**Table 2**) and the rural children (EC) (**Table 3**) and 4.8% [57] and 7.6% had low folate levels respectively,

An inflammatory response is initiated by damage to the vascular cell lining resulting in a series of mechanisms (acute-phase response) including haemodynamic (vasodilatation) activation of endothelial cells (increased adhesion molecule expression), increased permeability (enhanced protein movement) and an increase

thus at risk of impaired homocysteine metabolism and CVD.

*DOI: http://dx.doi.org/10.5772/intechopen.95992*

*5.7.3 Serum folate levels*

*5.7.4 Serum vitamin B12 levels*

#### *Double Burden of Poverty and Cardiovascular Disease Risk among Low-Resource Communities… DOI: http://dx.doi.org/10.5772/intechopen.95992*

synthesis requiring lysine and vitamin B6. Vitamin B6 deficiency was also found to be associated with decreased plasma PUFAs (n-6 and n-3) which may be associated with elevated cardiovascular risk and a contributing factor to the anti-inflammatory response. [104, 105] Low circulating vitamin B6 levels have been found inversely related to inflammatory markers (HS-CRP, fibrinogen, IL-6 and TNF-α) and are related to the incidence of inflammatory diseases (rheumatoid arthritis, CVD, and diabetes). [106, 107] Vitamin B6 levels were only available for the urban elderly and 98% of the respondents had low serum vitamin B6 levels (**Table 2**). Vitamin B6 levels were not available for any of the children, but pre-school children in Zambia indicated a suboptimal vitamin B6 in the studied group. [108] It would, therefore, be beneficial to include vitamin B6 serum levels in their analytical profile in future.
