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SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
VOLUME 15 NUMBER 2 • NOVEMBER 2018
45
important but vulnerable group. These studies show that long-
distance drivers have a significant burden of hypertension and
overweight/obesity, comparable to or even higher than in the
general population.
19-21
Hypertension is a common and important
CVD risk factor. Its prevalence among long-distance bus drivers
in Nigeria is 22.5%,
19
which was also the pooled prevalence of
hypertension in the general population in 2012.
22
However, none
of these studies screened the drivers for diabetes/abnormal glucose
profiles or dyslipidaemia.
Considering the potential risk associated with professional
driving, the importance of bus drivers to the country’s socio-
economic development and the paucity of data on the cardiovascular
risk profile of long-distance bus drivers, it became necessary to
investigate the prevalence of cardiometabolic and lifestyle-related
risk factors for CVD and their predictors in this segment of the
Nigerian working population in Lagos, south-west Nigeria. The
findings from this study will also help create awareness of their risk
burden and possibly help shape policies to address this risk.
Methods
This was a cross-sectional study involving male long-distance bus
drivers in major motor parks in Lagos. The parks were selected
based on their size and the routes they serve. Long-distance driving
was defined as a distance of 160-km radius from the terminal of
departure.
23
The calculated sample size was 268 based on the prevalence of
hypertension in the general population.
22
To allow for 15% attrition
rate, the sample size was increased to 308. However, 15 of the
drivers did not have complete data and were not included in the
data analysis, giving a response rate of 95%. Therefore 293 was
the final sample size used in the data analysis. Ethical approval for
the study was obtained from the Health Research Ethics Committee
of the Lagos University Teaching Hospital.
We used a stratified cluster-sampling method to recruit
longdistance drivers registered with the Transport Workers’ Union
from selected motor parks in Lagos between March and July 2015.
The motor parks were then stratified based on whether or not they
organised mandatory annual health and safety training for their
drivers (AHS motor parks). Only two motor parks employing 400
drivers met this criterion. The drivers in the AHS motor parks only
operate from their company terminals. We selected one of these
for inclusion in the study because its annual health and safety
programme coincided with the study period. All 168 drivers agreed
to participate but three (1.8%) later declined.
The second category of (non-AHS) motor parks comprised
independent drivers and drivers working for small transport
companies that operate from general and less regulated motor
parks in Lagos and who do not routinely receive formal health and
safety checks. We divided these motor parks into two; those serving
the northern and southern parts of the country, respectively. We
then randomly selected two motor parks from each of these strata
for inclusion in the study, thereby selecting four in total. Finally, we
used a convenience sample of 50 drivers from each of these four
parks and recruited 143 of them (71.5% response rate). Those who
declined did so due to time constraints and undisclosed personal
reasons. Fig. 1 shows the consort diagram on how the participants
were recruited.
On a mutually agreed day, the consenting drivers were
approached in groups and were given a talk on the importance of
healthy living and they were also briefed on the usefulness of the
study. They were told to observe an overnight fast on the day of the
medical screening. We used a structured questionnaire administered
by trained interviewers to obtain their sociodemographic data and
relevant medical history. Those who couldn’t read or write were
assisted to complete the questionnaire by interviewers who could
speak their native languages.
Thereafter their body weights were measured in kilograms with
an Omron HN289 (Osaka, Japan) digital weighing scale, placed on
a firm, flat ground, with participants wearing light clothing and
with no footwear or cap. Measurements were taken to the nearest
0.5 kg, after ensuring that the scale was always at the zero mark.
Their heights were measured in centimetres with a Seca model
216 (GmbH, Hamburg, Germany) stadiometer with the participant
standing erect, back against the height metre rule and occiput
and heels making contact with the height metre rule. BMI was
calculated as weight in kilograms divided by height squared in
metres.
24
BMI was categorised as underweight < 18.0 kg/m
2
;
normal weight 18.0–24.9 kg/m
2
; overweight 25.0–29.9 kg/m
2
;
class I obesity 30.0–34.9 kg/m
2
; class II obesity 35.0–39.9 kg/m
2
and class III obesity > 40.0 kg/m
2
.
Participants’ waist circumferences were measured with an
inextensible, inelastic 1-cm-wide tape snug around the body at the
level of the midpoint between the lower margin of the last palpable
rib and the top of the anterior iliac crest. Measurements were taken
at the end of normal respiration and ≥ 102 cm was regarded as
abdominal obesity.
25
Their neck circumferences were also measured
with an inextensible, inelastic 1-cm-wide tape at the level of the
cricoid cartilage. A neck circumference ≥ 40 cm defined obesity.
26
The blood pressure (BP) of the participants was measured by the
research assistants after five minutes of rest, with the participant
seated comfortably, feet on the floor, arm at the level of the heart
and free of any constricting clothing. Appropriate-sized cuffs and
bladder connected to an Omron HEM7233 (Osaka, Japan) digital
sphygmomanometer were used in measuring the BP, which was
taken initially on both arms, and the arm with the higher value was
used in subsequent measurements. Three BP readings were taken
at two- to three-minute intervals. The average of three readings
was taken for analysis. Hypertension was defined as BP ≥ 140/90
mmHg, self-volunteered history of hypertension and/or use of anti-
hypertensives.
Venepuncture was done on each participant while observing
aseptic techniques. Five millilitres of venous blood was put in fluoride
oxalate and lithium heparin vacutainer specimen bottles for fasting
plasma glucose and fasting lipid profiles, respectively, and sent to the
laboratory for processing and analysis with a Beckman (Pasadena,
CA, USA) automated clinical chemistry autoanalyser using standard
reagents/kits from Randox Laboratories.
27
Participants with a fasting
plasma glucose value of ≥ 126 mg/dl (6.99 mmol/l), self-volunteered
history of diabetes and or use of insulin/oral hypoglycaemic agents
were regarded as diabetic, while a fasting plasma glucose level
between 100 and 125 mg/dl (5.55–6.94 mmol/l) was regarded as
impaired fasting glucose.
28
For the purpose of this study, abnormal
glucose profile was defined as a combination of impaired fasting
glucose and frank diabetes.
Abnormal lipid profile was determined from the ATP III guidelines
of 2001; total cholesterol (TC) ≥ 240 mg/dl (6.22 mmol/l), high-
density lipoprotein cholesterol (HDL-C) ≤ 40 mg/dl (1.04 mmol/l),
and low-density lipoprotein cholesterol (LDLC) > 160 mg/dl (4.14
mmol/l) and triglycerides > 150 mg/dl (1.70 mmol/l).
29
Atherogenic