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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 29, No 3, May/June 2018
184
AFRICA
Methods
Adults aged 18 years and older were consecutively recruited
from individuals who visited the medical out-patient, cardiology,
neurology, hypertension and diabetes clinics of Obafemi Awolowo
University teaching hospitals complex (OAUTHC), Ile-Ife,
Nigeria, between January and December 2013. A total of 162
subjects were enrolled. Ethical approval was obtained from the
Ethics and Research Committee of OAUTHC, Ile-Ife, and written
informed consent was obtained from every study participant.
Demographic and clinical data such as age, gender, history of
hypertension, diabetes mellitus, chronic kidney disease, smoking
and alcohol intake were obtained by means of a structured
data sheet. Blood pressure was measured in line with practice
guidelines after 15 minutes of rest in the examination room,
before ultrasound of the carotid artery was done. With patients
seated comfortably, back supported, legs uncrossed, left upper
arm bare and supported at heart level, an appropriate bladder
cuff of an analogue mercury sphygmomanometer was applied
to the left upper arm to encircled 80% or more of the arm
circumference. After inflation, the mercury column was deflated
at 2 to 3 mm/s. The first and last audible sounds were taken
as systolic and diastolic blood pressure, respectively, and their
measurements were given to the nearest 2 mmHg. Neither the
patient nor the doctor taking the measurement talked during the
procedure. Two readings at one-minute intervals were taken, and
the average was recorded.
Weight and height were measured using a mechanical
physician’s weighing scale attached to a stadiometer (model
ZT-160, China). Body mass index (BMI) was calculated as
weight (kilograms) divided by height (metres) squared.
Venous blood samples were taken from each participant
between 07:00 and 08:00, after an overnight fast of eight hours.
Samples were centrifuged within two hours of collection at 3 000
g
for five minutes in a swing-bucket centrifuge, after which the
serum was separated into plain plastic screw-capped containers
and stored frozen at –20°C until analysis.
Samples were analysed in the chemical pathology department
of the hospital. Plasma samples were analysed for glucose
concentration (based on the glucose oxidase method) on the
day of collection, while serum samples were analysed for other
biochemical markers within one week of collection.
Creatinine (Cr) level was estimated in the serum with picric
acid (Jaffe’s reaction); total cholesterol (TC) was determined with
the cholesterol oxidase method; triglycerides (TG) were assayed
with the glycerol phosphate oxidase/peroxidase method; and
high-density lipoprotein cholesterol (HDL-C) was determined
with the precipitation method. Assay kits for lipid profiles were
purchased from Randox Laboratory Ltd, UK. Low-density
lipoprotein cholesterol (LDL-C) was calculated using the
empirical relationship of Friedewald’s formula:
10
LDL
=
total cholesterol – HDL-C – TG/5
All components of the lipid profile are given in mmol/l.
Normal values were taken as TC
≤
5.2 mmol/l, HDL-C
≥
1.03
mmol/l in men,
≥
1.30 mmol/l in women, LDL-C
≤
3.4 mmol/l,
and TG
≤
1.7 mmol/l, based on the National Cholesterol
Education Program Adult Treatment Panel III (ATP III).
10
Serum creatinine level is expressed in µmol/l, and values
between 80 and 115 µmol/l in males and 53 and 97 µmol/l in
females were considered normal.
10
Fasting blood sugar levels
of 4.1–5.6 mmol/l were considered normal.
10
These laboratory
assessments were done in collaboration with the chemical
pathologists.
Definitionof risk factorswas guidedby theATPIII guidelines.
10
Hypertension was defined as resting systolic blood pressure
(SBP)
≥
140 mmHg, and/or diastolic blood pressure (DBP)
≥
90
mmHg,
10
or use of antihypertensive drugs. Dyslipidaemia was
defined as use of antilipaemic drugs or having one or more of
the following: TC
≥
5.2 mmol/l, LDL-C
≥
3.4 mmol/l, HDL-C
≤
1.0 mmol/l, or TG
≥
1.70 mmol/l.
10
Diabetes mellitus (DM) was
defined as fasting blood glucose (FBG)
≥
7.0 mmol/l, or use of
antidiabetes medication.
10
A smoker was defined as a person who had smoked at least 100
cigarettes over his/her lifetime, including both current smoker (a
person who continued to smoke daily or occasionally at the time
of study) and past smoker (a person who had not smoked in the
past 12 months).
11
An alcohol consumer was defined as a person
who imbibed alcohol, including current consumer (a person who
had consumed alcohol in the past 12 months) and past consumer
(a person who had consumed alcohol in the past, but not in the
past 12 months).
11
A history of peripheral artery disease, myocardial infarction,
angioplasty, stroke or coronary artery bypass surgery was not
recorded in our study participants.
Carotid ultrasonography was performed using a Mind-ray
DC 7 ultrasound machine, equipped with a 7.5–12-MHz high-
resolution linear-array transducer. The common carotid artery was
scanned for CIMT and measurements were taken 10 mm from the
carotid bulb. Intima–media thickness was defined as the distance
between the leading edge of the lumen–intima and the leading edge
of the media–adventitia echo.
12
An average of the right and left
common carotid arteries (CCA) was taken for the study.
CA was defined as the presence of increased CIMT with
or without carotid plaque (CP). CIMT
≥
0.9 mm was taken as
increased CIMT.
12,13
Carotid plaques were recorded as present or
absent if seen or not, respectively. Plaque was defined as focal
thickening of at least 50% greater than that of the surrounding
vessel wall, with a minimal thickness of at least 1.5 mm.
12,13
Statistical analysis
All analyses were performed using the Statistical Package for the
Social Sciences (SPSS) statistical software (Version 20.0), SPSS
Inc. Continuous variables are represented as mean
±
standard
deviation (SD) while categorical variables are represented as
percentages. Group means of subjects with and without CVRFs
were compared using the Student’s
t
-test, while proportions were
compared using the chi-squared test. Bivariate logistic regression
was used to compare associations of subjects with CVRFs with
carotid atherosclerosis (increased CIMT or plaque presence) and
those without (normal CIMT or plaque absence). Only variables
with statistically significant associations on bivariate analysis
were included in the final multivariate logistic regression model
with the odds ratio and 95% CI presented. Significance was
taken at
p
<
0.5.
Results
Clinical, laboratory and anthropometric characteristics of the
subjects are shown in Table 1. The mean age of the study
participants was 51.96
±
15.09 years and 49.4% were male. The