CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 4, July/August 2022 AFRICA 171 and blood sampling starting after the resting phase. Feedback was given to the participants on immediately available clinical measures in the privacy of their rooms, by a registered nurse, and referrals were made if deemed necessary. After breakfast the participants were transported back to their respective schools. The CSI questionnaire was validated for use in ethnic groups and used to determine the coping strategies utilised during stressful situations.16,35 Before the participants started with the written questionnaire, they had to recall a stressful problem or incident they had encountered in the past six months, while bearing in mind their manner of coping therewith. Each participant’s coping strategy was assessed using both deductive and inductive methodologies. The three coping strategies that formed part of the 33-item CSI questionnaire included: active problem solving or DefS, avoidance or loss of control, and seeking social support. The three sub-scales were assessed by dividing the 33 items into three sets of 11 questions. These questions were randomly ordered in the questionnaire. According to the answer, every item was assigned a numerical value, namely: a lot (three points), a little (two points), or not at all (one point). A maximum score out of 33 was calculated for each sub-scale. The above-median coping scores included:16 26–33 for DefS, 23–25 for social support coping and 19–22 for avoidance coping. High scores within each coping strategy sub-scale (≥ 31 for DefS, ≥ 28 for social support, ≥ 23 for avoidance coping) indicated preferred use of that strategy.16 The reliabilities, as measured by Cronbach α-coefficients for the SABPA study, were 0.83 for DefS, 0.84 for seeking social support coping and 0.69 for avoidance coping. The BTI questionnaire was developed by Taylor and de Bruin24 for a South African context and measures the ‘big five’ factors of personality.25 The use of the BTI questionnaire was validated across different culture and language groups in South Africa.36 The five factors consist of certain facets and include the following: extraversion (positive affectivity, gregariousness, excitement seeking, ascendance, liveliness), neuroticism (anxiety, selfconsciousness, depression, affective instability), conscientiousness (self-discipline, order, effort, dutifulness, prudence), openness to experience (actions, aesthetics, ideas, values, imagination) and agreeableness (compliance, straightforwardness, tendermindedness, modesty, pro-social tendencies). The questionnaire includes 193 written statements covering the different facets for each factor. The participants had to indicate the degree to which they agreed with the statement that was measured on a five-point Likert scale ranging from ‘strongly disagree’ to ‘strongly agree’. These items were alternated with a 13-item social desirability scale, which also forms part of the BTI. Scores of 40–60 for individual personality traits were considered to be average, while low and high scores were reported as any score < 40 and > 60, respectively.24,37 The Cronbach α-coefficients calculated for the SABPA study to indicate reliability of personality traits included: extraversion (0.81); neuroticism (0.88); conscientiousness (0.90); openness to experience (0.85) and agreeableness (0.83). Level II anthropometrists used standardised procedures when they obtained three anthropometric measurements, using the mean for analysis. Waist circumference was taken at the midpoint between the lower costal rib and the iliac crest, vertical to the long axis of the trunk. The Actical® omnidirectional accelerometer (Montreal, Quebec, Canada) measured total energy expenditure of the participants as an indication of physical activity. A registered nurse obtained fasting blood samples from the participants’ antebrachial vein branches. Standardised procedures were followed regarding preparation and storage of samples at –80°C until analysis. Serum cotinine and gammaglutamyl transferase (GGT) were respectively used as biochemical markers for smoking status and alcohol consumption.38,39 Cotinine was measured by means of a modular Roche automised (Switzerland) apparatus using a homogeneous immunoassay. Cotinine, ametabolite of nicotine, defined habitual smokers when levels were ≥ 14.99 ng/ml.38 Serum GGT, total cholesterol and high-density lipoprotein (HDL) cholesterol were determined with the Unicel DXC 800 (Beckman and Coulter, Germany) and the KonelabTM 20I sequential multiple analyser computer (Thermo Scientific, Vantaa, Finland) at baseline, and with the Integra 400 (Roche, Switzerland) apparatus during follow up. The total cholesterol to HDL cholesterol ratio was calculated at both baseline and follow up. Serum cTnT, N-terminal pro-brain natriuretic peptide (NT-proBNP) and oestradiol were analysed using the electrochemiluminescence immunoassay on the Cobas e411® (Roche, Basel, Switzerland). In the current cohort, 83 (24.7%) cTnT values were below the detection limit of 3 pg/ml and these values were substituted with log-transformed values, which were calculated using the Croghan and Egeghy method for underthe-limit-of-detection values.40 The turbidimetric inhibition immunoassay method was used to measure whole blood EDTA glycated haemoglobin A1c (HbA1c) (Cobas Integra 400 plus; Roche, Basel, Switzerland). The Cardiotens® CE120 (Meditech, Budapest, Hungary), recording 24-hour BP and ECG, was fitted to the non-dominant arm of each participant. This device was programmed to measure BP every 30 minutes between 08:00 and 22:00 and every 60 minutes between 22:00 and 06:00.41 The 24-hour data were analysed using the CardioVisions 1.19 personal edition software (Meditech, Budapest, Hungary). A mean 24-hour systolic blood pressure (SBP) ≥ 130 mmHg and/or diastolic blood pressure (DBP) ≥ 80 mmHg was regarded as hypertensive.42 Statistical analyses All data analyses were done with Statistica version 13.3 (TIBCO Software Inc, Palo Alto, USA, 2018). Visual inspection of Q-Q plots, followed by Kolmogorov–Smirnov and Lilliefors tests, were performed to test normality of data, and non-normally distributed data were Box–Cox transformed. Before continuing with any analyses, interactions were computed to determine how groups should be divided. Interactions on main effects [race × gender × high DefS/seeking social support coping/ avoidance coping] for each of the personality traits and threeyear percentage change (%Δ) in cTnT level, independent of a priori selected covariates were tested with a three-way analysis of covariance (ANCOVA). The a priori covariates included age, and cotinine and GGT levels at baseline.42-45 Independent t-tests were performed to compare general and clinical characteristics between the two races. Pearson’s chi-squared (χ2) test was used for determining prevalence and proportions. Mean differences in cTnT levels between baseline
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