Q UESTIONNAIRE DEVELOPMENT AND VALIDATION

The structured body shape questionnaire (BSQ), with a section on CVD risk assessment was developed for data collection based on the adapted BSQ of Mciza (34,195). This questionnaire also had adapted aspects of the validated ‘Attitude and Belief Questionnaire’ used by Matoti-Mvalo and Puoane (79). Subjective questions were inserted with corresponding statements to further validate key questions asked.

Participants were given three options (agree, uncertain and disagree) from which to select an answer for each statement (in Sections B & C of the questionnaire). The questionnaire was pre-tested among 10 isiXhosa-speaking adults in Langa and the results guided the modification for use in the study settings. The final version of the structured questionnaire had three subsections, (i) perception, (ii) attitude and (iii) perceived consequences of body image and control of overweight.

3.6.3 Data collection

In this third phase, information on body-image perceptions, CVD risk factors and lifestyle behaviours and medical history were collected during a cross-sectional survey. In addition, anthropometric measurements including height, weight, and body fat (using a bio-electric impedance analysis (BIA) device) and waist circumference were taken based on the standard procedures in the main study protocols (39). The questionnaire was administered during the PURE study follow-up survey between June 2014 and July 2015.

Five trained research assistants undertook the data collection under the supervision of the  

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Blood pressure (BP) measurements were taken at short intervals using Omron BP devices and averages recorded as actual BP measures. In addition, baseline physical measurements (weight, height, WC) were obtained from the PURE study baseline dataset for analysis and comparison purposes. Procedures adopted for the interviews, anthropometry, CVD risk scores and body-image perception measurements are discussed in detail below.

Interviews

Face-to-face interviews were conducted with men and women using an interviewer-administered structured questionnaire (Appendix 4). The Stunkard Figures rating scale validated by Mciza et al. (123) and adapted for use among the South African population was used to objectively collect information on body-image perceptions. Sex-specific Stunkard Figures rating scale with figures, ranging from very thin (1) to grossly obese (8) were presented to the participants to select a figure corresponding to the questions. This was done to rate perceptions and attitudes of participants about body image and overweight/obesity. Interviews were conducted with the only willing participant(s) in each sampled household.

Anthropometry and blood pressure measurements

Anthropometric measurements were recorded using the standardised protocol adapted for the PURE study. Height was measured to the nearest 0.10 cm using a height metre with the subject standing erect. Weight was measured with a calibrated digital weighing scale (a-300 Precision Health Scale), set at “0” (zero) prior to each measurement. These measurements were taken with subjects wearing light clothing and without shoes. WC was measured with the subject standing erect with the abdomen relaxed and arms at the

sides. Each WC measurement was carefully taken over the minimally-clothed/unclothed abdomen at the smallest diameter between the costal margin and the iliac crest (39). In addition, systolic and diastolic BP measurements were taken on the left arm with the participant seated using Omron BP measuring device. The average of two measures constituted the actual BP.

Body fat and body composition

Body fat percent and other body composition such as total body water, bone mass, and visceral fat were recorded using the standard BIA device (Tanita Ironman body composition monitor BC-554, Tanita Corporation 2009, UK). To ensure accuracy, readings were taken with participants standing erect with clean soles of the feet and heels correctly aligned on the measuring platform. The subjects’ height, age, and sex were entered into the device for analysis and the respective body compositions were recorded.

Pregnant women and individuals with an electronic medical implant were exempted from BIA measurement with Tanita BIA device as stipulated in the operation manual. This study was mostly concerned with BF%.

Cardiovascular risk scores estimation using Framingham cardiovascular risk equations

Each study participant was evaluated for total CVD risk using the D’Agostino Framingham Heart Study equation to estimate an individual’s 10-year risk for a CVD event (204). To obtain a total 10-year risk score for each participant based on the BMI, sex-specific equations based on six non-blood based risk factors (i.e. age, sex, SBP, diabetes, treated for hypertension status, and BMI (instead of lipids)) were entered into

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CVD disease prediction equations to generate the CVD scores. The following detail linear equations were used:

The Linear equation (L) were computed for each participant based on sex, where:

Equation 1: L(men) = (3.067 x log of age) + (1.93303 x log of SBP) [if treated for hypertension] + (1.99881 x log of SBP) [if not treated for hypertension] + 0.65451 [if smoker] + 0.0 [if non-smoker] + 0.57367 [for diabetes status] + 0.79277 x log of BMI.

Equation 2: L(women) = (2.32888 x log of age) + (2.76157 x log of SBP [if treated for hypertension] + (2.82263 x log of SBP [if not treated for hypertension] + 0.52873 [if smoker] + 0.0 [if non-smoker] + 0.0.69154 [for diabetes status] 0.51125 x log of BMI.

The individual risk score is an estimate of the probability of a cardiovascular event occurring in ten years, taking into account CVD outcome, duration of follow-up, population of interest, and predictors. CVD risk score was used as a continuous variable and described in a dichotomous category (‘high’, and ‘low’) to aid analyses. The CVD-risk scores form the outcome (dependent) variable, which is used to test a possible relationship with independent variables such as body image and BF% to determine how body image and BF% contribute individually or together to CVD risk among men and women. A conventional threshold for CVD risk (10-20%) was used as the optimal or the normal risk CVD level. A risk score of ≤20% was considered as ‘low’, and ≥20 as ‘high’

risk (32,237).

Perception of body size

To measure body-size perception and weight discordance, the study participants were asked to select a figure that closely resembled their body size status from a set of

silhouettes – the Body Image Figure Rating Scale ranging from the very thin to very heavy (10,34). Participants’ perceived body image (‘Feel’ size) as selected from the body image silhouettes was compared to their perceived ‘Ideal’ size to determine how accurately an individual perceives their body image. Further, individuals were asked to select the silhouette that resembles the ‘ideal’ size they wanted to look like from the same set of silhouettes. The FID index determined by subtracting the score of the silhouettes is then used to determine an individual’s attitude towards their own body size (34,146). Feel-actual discordance (FAD) index was also obtained by subtracting the measured (‘Actual’

weight) score from the corresponding measured (BMI weight) from the ‘feel’ weight.

FAD indicates the discordance in self-assessed weight for each participant.

3.6.4 Data analysis

The analyses for this phase of the study was based on the 963 PURE study cohort participants for which data were collected at year-4 follow-up. Descriptive statistics were reported using frequencies, means and standard deviations (SD), and bivariate analyses were undertaken. P-value <0.05 at 95% confidence interval (CI) was used as the statistical significant level, unless otherwise stated. The analyses were restricted to the 920 PURE cohort participants with no known CVD event; 43 participants with known CVD were excluded. This sub-sample represents approximately 75% of the existing PURE study cohort participants.

Participants’ weight, adiposity (body fat) categories and CVD-risk profiles by sex and location were determined, and CVD-risk scores were compared in the obese and non-obese participants. Adiposity categories in the study were based on BMI, WC, BF%, and WTHR standard cut-offs (170). Student t-tests were used to establish the difference in the

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of variance (ANOVA) and chi-square tests respectively were used to determine the patterns of 10-year CVD risk and body image (FID and FAD) categories based on the age of participants. The prevalence of body image based on adiposity were presented graphically, with significant levels determined at p>0.05 based on chi-square tests.

The associations among body-image perceptions (FID and FAD) and weight and adiposity were determined using Pearson’s r coefficient. Scatter plots were used to show the relationship between body image and weight change over time. Partial correlation analysis was used to determine the correlation between FID, FAD and 10-year absolute CVD-risk score, controlling for the modifiable risk factors. Logistics regression models were used to determine the factors associated with body image (i.e. discordant weight status and size dissatisfaction). Full details of the data analyses are presented in Chapter 6, section 6.2 under ‘Data analysis’.