The SA Journal Diabetes & Vascular Disease Vol 13 No 2 (December 2016)

VOLUME 13 NUMBER 2 • DECEMBER 2016

REVIEW

SA JOURNAL OF DIABETES & VASCULAR DISEASE

and Senegal with smoking rates of 27.5, 27.1, 22.0 and 19.8%,

respectively. Even in Nigeria and Ghana, where smoking rates were

relatively low before 2003, estimated at 6.1% in Nigerian men,

0.1% in Nigerian women, 4.6% in Ghanaian men and 0.2% among

Ghanaian women, overall smoking prevalence more than doubled

in men to 13 and 10.2% in Nigeria and Ghana, respectively in 2009

but remained quite low in women.

Although deaths from tobacco-related causes probably

accounted for only 5 to 7% in African men and 1 to 2% in African

women in the year 2000,

by 2030, tobacco is expected to be the

greatest contributor of deaths in SSA. Most victims will die 20 to 25

years prematurely of various cancers, respiratory diseases, IHD and

other circulatory disorders.

Regrettably, most governments in African countries have

avoided action to control smoking for fear of harmful economic

consequences on their fragile economies. Without effective

tobacco-control measures, SSA risks becoming the biggest global

ashtray as many transnational tobacco companies shift their targets

to middle- and low-income countries.

Dyslipidaemia

There is overwhelming epidemiological evidence implicating

cholesterol as a cause of atherosclerosis. Most black Africans

reportedly have low levels of total cholesterol associated with

high high-density lipoprotein (HDL) cholesterol levels.

Higher

cholesterol levels however, have been found in diabetic patients

from Zimbabwe and Tanzania. The total serum cholesterol was

also significantly higher in women than men. Reports from West

Africa indicate a worrying trend of dyslipidaemia among patients

with either type 1 or type 2 diabetes mellitus.

Data from the

Transition of Health during Urbanisation of South Africa (THUSA)

study indicate that black South Africans may be protected from

IHD because of favourable lipid profiles characterised by low total

cholesterol and high HDL cholesterol levels.

In Nigeria, IHD contributes very little to mortality rates in middle-

aged men and women, partly because of particularly low mean

cholesterol levels.

Different black African communities may be at

different stages of their epidemiological transition, as shown in an

epidemiological study of coronary heart disease risk factors in the

Orange Free State in South Africa.

Table 4 illustrates this point

quite vividly. Selected countries representing the different regions

of SSA show wide differences in mean total cholesterol levels with a

tendency to higher cholesterol levels in females in some countries.

The cardiovascular impact of HIV/AIDS

SSA bears a disproportionate share of the global HIV burden. The

interaction between HIV infection, acquired immunodeficiency

syndrome (AIDS), its treatment with highly active antiretroviral drugs

(HAART), and cardiovascular disorders is complex and incompletely

understood.

The transformation of HIV/AIDS into a chronic disorder with the

advent of antiretroviral drugs is associated with the emergence

of certain characteristic cardiovascular risk factors, and raises

apprehension about the potential increase in prevalence of

cardiovascular diseases, including IHD, in SSA. In Botswana, for

instance, where antiretroviral therapy coverage exceeds 90%,

AIDS-related deaths declined by approximately 50% between 2002

and 2009.

The repertoire of immunological responses associated with

acute and chronic HIV infection is quite complex and will be only

highlighted here. Perturbations of cytokine expression, cellular

dysfunctions, redistribution of lymphocyte sub-populations,

increased cellular turnover and apoptosis are some of the

features of general activation of the host’s immune system that

characterise chronic HIV infection.

Chronic HIV infection, and

not its pharmacological treatment, induces changes in markers of

endothelial function.

Untreated HIV infection is also associated

with impaired elasticity of both large and small arteries.

Some authors have suggested that HIV infection accelerates

atherosclerosis via a pro-inflammatory effect on the endothelial cells

through the effects of various cytokines, especially interleukin-6 and

D-dimers.

44,45

Other mechanisms of arteriopathy include the direct

toxic effects of HIV-associated g1p20 and tat proteins on vascular

or cardiac cells. There is also evidence of a hypercoagulable state,

which inversely correlates with CD4 count.

Although traditional risk factors for cardiovascular diseases

might overshadow the role of non-traditional risk factors, there

is increasing evidence that young, asymptomatic, HIV-infected

men with long-standing HIV disease demonstrate an increased

prevalence and degree of coronary atherosclerosis compared with

non-HIV-infected patients.

Furthermore, HIV-infected patients

tend to develop perturbations in lipid metabolism, characterised

by decreased HDL cholesterol and low-density lipoprotein (LDL)

cholesterol levels, followed by an increase in plasma triglyceride

levels pre-HAART and prior to developing AIDS.

Both traditional and non-traditional risk factors therefore appear

to contribute to atherosclerotic disease in HIV-infected patients.

Those on HAART, particularly protease inhibitors, develop a myriad

of class- and non-class-specific metabolic effects on lipid profiles,

glucose levels, insulin sensitivity and anthropometric body changes

characteristic of lipodystrophy. UntreatedHIV infectionmay alsohave

a paradoxical overall effect on cardiovascular disease and thereby

reduce the risk of ischaemic heart disease because of severe and

progressive weight loss, wasting syndrome, hypotension resulting

Table 4.

Estimated mean total cholesterol in selected African countries

by region in females and males aged 15 years and older, 2011.

Region/country

Females mean total

cholesterol (mmol/l)

Males mean total

cholesterol (mmol/l)

Eastern Africa

Uganda

UR Tanzania

4.4

5.2

4.7

4.4

Central Africa

DR Congo

Rwanda

4.3

Western Africa

Nigeria

Ghana

3.7

5.9

3.6

4.4

Southern Africa

Botswana

South Africa

4.7

4.4

4.7

4.4

Islands

Mauritius

Seychelles

5.2

5.9

5.2

5.8

DR Congo = Democratic Republic of Congo, UR Tanzania = United Republic

of Tanzania.

Source:

https://apps.who.int/infobase/Comparisons.aspx

Accessed on 31

December 2011