CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 3, April 2013
AFRICA
67
The Global Study on Ageing (SAGE) survey was carried
out in South Africa in partnership with the World Health
Organisation (WHO), the National Department of Health, and
the Human Sciences Research Council (HSRC). The study was
approved by the Human Sciences Research Council Research
Ethics Committee and the national Department of Health.
Blood pressure (systolic and diastolic) was measured three
times on the right arm/wrist of the seated respondent using
an automated recording device (OMRON R6 Wrist Blood
Pressure Monitor, HEM-6000-E, Omron Healthcare Europe, BV,
Hoofddorp and The Netherlands).
Out of three measurements, the average of the last two read-
ings was used. In accordance with the Seventh Report of the Joint
National Committee on Prevention, Detection, Evaluation and
Treatment of High Blood Pressure, individuals with systolic blood
pressure
≥
140 mmHg and/or diastolic blood pressure
≥
90 mmHg
and/or who reported the current use of antihypertensive medica-
tion were considered to be suffering from high blood pressure.
28
Awareness was defined as history of hypertension based on
diagnosis by a healthcare provider. Treatment was defined as
taking any medication or other treatment for hypertension in the
last two weeks prior to the survey, and control was defined as
blood pressure
<
140 and
<
90 mmHg at the time of the survey.
Lifetime tobacco users were asked ‘Do you currently use
(smoke, sniff or chew) any tobacco products such as cigarettes,
cigars, pipes, chewing tobacco or snuff?’ The response options
were ‘Yes, daily’, ‘Yes, but not daily’ and ‘No, not at all’. Daily
tobacco use was coded
=
1, and not daily and not at all
=
0.
29
Lifetime alcohol users were asked about current (past month)
alcohol use. Past month alcohol use was coded
=
1 and no past
month alcohol use
=
0.
Height and weight were measured. Body mass index (BMI)
was used as an indicator of obesity (
≥
30 kg/m
2
), calculated as
weight in kg divided by height in metres squared. Overweight
and/or obesity were defined as BMI
≥
25 kg/m
2
and underweight
as
<
18.5 kg/m
2
.
Social cohesion was measured with nine items, starting with
the introduction ‘How often in the last 12 months have you… e.g.
attended any group, club, society, union or organisational meet-
ing?’All nine items were summed to get a social cohesion index.
Response options ranged from never
=
1 to daily
=
5. Cronbach
alpha for the social cohesion index in this sample was 0.73.
Physical activity was measured using the General Physical
Activity Questionnaire (GPAQ). The instrument gathers
information on physical activity in three domains (activity at
work, travel to and from places, and recreational activities),
as well as time spent sitting. The questionnaire also assesses
vigorous and moderate activities performed at work and for
recreational activities. Information on the number of days a week
spent on different activities, and time spent in a typical day for
each activity was also recorded.
30
Cronbach alpha for the GPAQ
in this sample was 0.77.
For physical activity, in addition to the total minutes of
activity, the activity volume was also computed by weighting
each type of activity by its energy requirement in metabolic
equivalents (METs). One MET was defined as the energy cost
of sitting quietly, and was equivalent to a caloric consumption
of 1 kcal/kg/h. A MET-minute showed the total activity volume
on a weekly basis, and was calculated by multiplying the time
spent on each activity during a week by the MET-values of each
level of activity. MET-values for different levels of activities were
set as 4 MET for moderate intensity physical activity, 8 MET
for vigorous physical activity, and 4 MET for transport-related
walking or cycling.
The total physical activity for GPAQ2 was calculated as
the sum of the total moderate, vigorous, and transport-related
activities per week. The number of days and total physical
activity MET-minutes per week were used to classify respondents
into three categories of low, moderate and high level of physical
activities. Less than 600 MET-minutes per week was classified
as low physical activity.
30
Fruit and vegetable consumption was assessed with the
questions ‘How many servings of fruit do you eat on a typical
day?’ and ‘How many servings of vegetables do you eat on a
typical day?’ Insufficient fruit and vegetable consumption was
defined as less than five servings of fruits and/or vegetables a day.
Overall self-rated health status was based on respondents’
assessment of their current health status on a five-point scale
in response to the question: ‘In general, how would you rate
your health today?’ Response categories were: very good, good,
moderate, bad and very bad. Very good and good were grouped
together and coded
=
1, moderate
=
2 and bad and very bad were
grouped together and coded
=
3.
Activity limitation (difficulty an individual may have in
executing task or actions) was assessed with one item ‘Overall in
the last 30 days, how much difficulty did you have with work or
household activities?’ Response options ranged from 1
=
none to
5
=
extreme/cannot do. None were coded
=
1, mild
=
2, moderate
=
3 and severe and extreme were grouped together and coded
=
4.
Finally, participants were asked about a list of chronic and other
conditions they had been diagnosed with, including diabetes,
hypertension, stroke, angina and arthritis. Of participants who
responded to having been diagnosed with hypertension, the
question was asked, ‘Have you been taking any medication or
other treatment for it during the last two weeks?’ Other treatment
might include a weight-loss programme or change in eating
habits.
Attendance at out-patient care was assessed with the question,
‘Over the last 12 months, did you receive ant healthcare not
including an overnight stay in hospital or long-term care
facility?’ Of those who indicated ‘yes’ they had to report the
number of times they had received healthcare or consultation in
the last 12 months. Frequency of attendance at out-patient care
was grouped into none
=
0, one to four
=
2, five or more
=
3.
To estimate economic or wealth status, a random-effects probit
model was used to identify indicator-specific thresholds that
represent the point on the wealth scale above which a household
is more likely to own a particular asset than not. This enabled
an estimation of an asset ladder. These estimates of thresholds,
combined with actual assets observed to be owned for any given
household, were used to produce an estimate of household-level
wealth status. This was used to create wealth quintiles.
31
Lowest
and second-lowest wealth quintiles were grouped together as low
=
1, the middle wealth quintile was medium
=
2 and the fourth
and highest wealth quintiles were grouped together as high
=
3.
Statistical analysis
The data were entered using CSPro and analysed using STATA
Version 10. The data were weighted using post-stratified
