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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 2, March/April 2015
58
AFRICA
Determining the level of sodium intake in the population
is crucial to establish intervention strategies and policy on
reduction of sodium intake. For medical students in particular,
it is very important to assess their awareness regarding dietary
salt intake, since they are the future providers of healthcare
information for the counselling of people about the need to
reduce salt consumption. The aim of this study was to determine
salt intake and to assess the knowledge, attitude and behaviour
regarding dietary salt among medical students.
Methods
Participants were undergraduate medical students randomly
recruited from a population of 625 students listed in 2013 at
the Faculty of Medicine of the University Agostinho Neto
(FMUAN) in Luanda, Angola. Due to limited resources, the
study was planned to collect 24-hour urine samples from 30% of
the students (
n
=
188) representative of the student population.
Data were collected from September to October 2013 in the
Department of Physiology of FMUAN.
The protocol of the study was in agreement with the
Declaration of Helsinki and approved by the institutional review
board. Each participant gave informed, written consent, and no
compensation was given for participation in the study.
For recruitment, the academic secretary of FMUAN provided
a list of all students from first to fifth year. We randomly selected
30% from each year and contacted them by phone one day
later to invite them to participate in a cross-sectional survey on
‘cardiovascular risk factors’. A participant information sheet and
a consent form explaining the purpose and protocol of the study
were also provided. If participation was declined, another student
from the same academic year, gender and age group was contacted.
Thus 188 students were randomly selected from 625 registered
students, and 153 agreed to participate. Of these, seven subjects
were excluded as they met the exclusion criteria [being pregnant (
n
=
1), having a history of hypertension or taking anti-hypertensive
medication (
n
=
6)]. A further 23 students were excluded from the
analyses due to incomplete 24-hour urine collections [i.e. 24-hour
urine volume
≤
500 ml (
n
=
5); urine loss more than once in 24
hours (
n
=
7), timing of the urine collection less than 23 hours
(
n
=
11)]. Final analyses were undertaken on 123 participants (54
men and 69 women) with valid urine collections.
Data collection
A standardised questionnaire was administered for each
participant to obtain demographic data and information on
medical history, smoking habits, intake of alcohol, use of
medication and physical activity. Participants’ awareness of a
diagnosis of hypertension was based on having previously been
informed on the diagnosis of the condition, receipt of therapy for
it, or an awareness of the purpose of antihypertensive therapy.
Relevant knowledge, attitude and behaviour on dietary salt were
assessed using a standardised questionnaire from the WHO.
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Participants were classified as non-smokers (never and
ex-smokers) and current smokers (daily and occasional smokers).
Alcohol consumption was assessed on their answer to the
question about consumption of alcoholic beverage (‘yes/no’).
Physical activity was assessedwith the following two questions:
‘Do you currently participate in any regular physical activity for
leisure (‘yes/no’)? If ‘yes’, what frequency per week? Participants
were classified as sedentary or inactive if they answered ‘no’ to
the first question or reported a frequency of regular physical
activity less than three days per week. They were considered
active if they reported regular physical activity at least three days
a week of at least 30 minutes or more per session.
Study protocol and laboratory tests
Clinical examinations were performed between 08:00 and 12:00
in temperature-controlled rooms (22–23°C) after a 10- to 12-hour
fast. Participants were asked to refrain from smoking, physical
exercise and caffeinated beverages before the visit.
Venous blood samples were obtained from the forearm
using standard techniques and processed immediately with
commercially available kits (BioSystems SA, Costa Brava
30, Barcelona, Spain) for determination of levels of serum
triglycerides, total cholesterol, glucose, creatinine and uric acid.
Biochemical parameters were analysed using enzymatic methods
with a spectrophotometer (BioSystems BTS-350, Costa Brava
30, Barcelona, Spain). Diabetes was defined as a fasting glucose
level
≥
126 mg/dl (7 mmol/l) or the use of antidiabetic drugs.
25
Urine was collected during the 24-hour period preceding the
clinic visit. Participants were asked to collect all urine they passed
during a 24-hour period starting from the second urination on
the morning of the collection day, and ending with the first urine
passed the following morning. In order to maximise a correct
24-hour urine collection, participants were asked to collect their
samples from Sunday 7:00 to Monday 7:00.
Participants were also asked to note on the record sheet
the start and finish times of their urine collection, if some
urine was lost, and any medication taken during the collection
period. Females were encouraged to collect their urine on
non-menstruation days.
For the collection, participants were provided with urine
collection kits and standardised written instructions on how
to collect and handle urine. The urine collection kit comprised
five-litre plastic bottles with screw caps to serve as the collection
container for urine; two-litre plastic bottles with screw caps for
collections made away from home; one-litre plastic jugs; one
funnel and a plastic carrier bag for transporting the equipment
from home.
Participants were instructed to pass urine into the one-litre
plastic jug, and then pour the sample into the five-litre container
using the funnel provided. Plastic bags were provided to carry the
equipment (including a smaller two-litre collection container) if
participants were not at home for some of the collection period.
The validity of 24-hour urine collection was verified by a
combination of three criteria. Urine samples were considered
incomplete for a 24-hour collection period and excluded from
analysis if: (1) there was more than one self-reported loss of
a urine sample; (2) a 24-hour urine sample measured at the
laboratory was
≤
500 ml/day; (3) timing of the urine collection
was less than 23 hours or more than 25 hours.
After validation, a sample of 60 ml was centrifuged at 3 500
rotations/minute, using a Sigma 2-6E device (Germany), before
aliquots were sampled. The urine was transferred in duplicate into
screw-top plastic test tubes. The aliquots were kept in a freezer
within 24 hours of collection and stored at –15ºC until analysed
in the laboratory at the Department of Biochemistry of FMUAN.