CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 1, January/February 2011
18
AFRICA
Smoking and vascular dysfunction in Africans and
Caucasians from South Africa
MC ZATU, JM VAN ROOYEN, AE SCHUTTE
Summary
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.
Keywords:
smoking, vascular dysfunction, socio-economic
status, ethnicity, Africans, Caucasians
Submitted 28/10/09, accepted 14/3/10
Cardiovasc J Afr
2011;
22
: 18–24
CVJ-21.016
It is well known that smoking has negative health consequences
and it is the main avoidable cause of illness and death world-
wide.
1
Smoking causes many premature deaths annually in the
world.
1,2
Despite the negative effects of smoking, the continuous
use of tobacco products is rising.
3
Globally, the prevalence of
smoking-related cardiovascular diseases (CVDs) is higher in
Africans than Caucasians.
4-6
In South Africa, factors such as age,
gender, ethnicity, cultural and economic characteristics influ-
ence the prevalence of smoking.
7,8
There is a high prevalence of
smoking in adults, mostly white males and those earning a low
income.
7,9
However, it has been shown that poorer smokers are
more likely to quit than smokers who are more affluent.
9
Many studies have reported on the effect of smoking on the
metabolic syndrome, which is a highly prevalent cluster of disor-
ders that are relatively common in Africans.
10-12
Smoking and the
metabolic syndrome together cause dyslipidaemia, increased
C-reactive protein (CRP) levels and endothelial dysfunction.
11,13
Smokers are therefore characterised by high serum triglycerides
(TG) and low-density lipoprotein cholesterol (LDL-C), with
significantly lower high-density lipoprotein cholesterol (HDL-C)
than non-smokers.
4
Nicotine in cigarette smoke increases heart rate (HR) and
cardiac output (CO) through cardiac beta-adrenergic effects,
1
leading to increases in blood pressure (BP). Carbon monoxide
decreases the oxygen-carrying capacity of the blood and may
lead to ischaemia and hypoxia of the tissues.
4,14
This stimu-
lates increased red blood cell production, which contributes to
increased viscosity and consequently inflammatory and coagula-
tory processes.
4
Both inflammation and coagulation are associ-
ated with atherosclerosis and coronary heart disease.
15,16
All these
factors therefore contribute negatively, in one way or the other, to
increased risk for CVD.
Nicotine is broken down metabolically into various metabo-
lites that include cotinine and nicotine-N-oxide.
3
The most
important metabolite of nicotine is cotinine,
3,17
which is a vital
biological marker of smoking and has been used to identify
smokers.
3,18
Serum cotinine levels of smokers are consequently
significantly higher than non-smokers.
3
The association between smoking and CVD has been well
documented in developed countries.
1,4
However, limited data
exist in low- and middle-income countries such as South Africa.
The aim of this study was to determine if there are ethnic differ-
ences regarding the association between smoking and measures
of cardiovascular function between African and Caucasian
people of South Africa.
Methods
This was a sub-study based on data from the SAfrEIC study
(South African study on the influence of sex, age and Ethnicity
on Insulin sensitivity and Cardiovascular function). The SAfrEIC
study was a cross-sectional study with 630 participants (appar-
ently healthy African and Caucasian men and women) from
urban areas of the North West Province of South Africa, aged 20
to 70 years. Exclusion criteria for this sub-study were diabetes
(type 1 and 2), or persons on diabetic medication, pregnant or
breast-feeding women, and those testing positive for the human
immunodeficiency virus (HIV).
The Ethics committee of the North-West University
(Potchefstroom campus) approved this study. The partici-
pants signed informed consent forms after all procedures were
explained to them. An interpreter was available to relay the infor-
mation to the African subjects in their home language.
For a period of seven weeks, 10 to 20 participants visited
the facility daily (consisting of 10 bedrooms, two bathrooms, a
living room and kitchen) on the Potchefstroom campus of the
North-West University. They arrived at 07:00 and four field
Hypertension in Africa Research Team (HART), School for
Physiology, Nutrition and Consumer Sciences, North-West
University, Potchefstroom, South Africa
MANDLENKOSI C ZATU, MSc
JOHANNES M VAN ROOYEN, DSc
ALETTA E SCHUTTE, MSc, PhD,
