CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 4, July/August 2022 172 AFRICA and three-year follow up were determined by means of dependent sample t-tests within African and Caucasian groups. Effect sizes for independent and dependent sample t-tests were determined by calculating Cohen’s d (0.2 = small effect, 0.5 = medium effect and 0.8 = large effect), while phi (φ)-values for Pearson’s chi-squared tests indicated effect sizes (0.1 = small effect, 0.3 = medium effect and 0.5 = large effect).46,47 McNemar case–control tests determined three-year incidence (negative at baseline becomes positive at follow up) and recovery (positive at baseline recovers to negative at follow up) frequencies for ethnic-specific cTnT cut-off points in Africans and Caucasians.4,13 The following formula was used to calculate %∆ over a period of three years: %∆ = (follow-up value – baseline value) __________________________ baseline value × 100. Pearson’s correlations determined relationships between coping scores and personality traits in Africans and Caucasians. In an attempt to gain more insight into the role of personality traits and genetic influences, paired samples correlations were also used to determine linear relationships between the BTI traits and available gene data [maternal lineage/mitochondrial DNA,48 catecholamine-synthesis trigger enzyme/tyrosine hydroxylase C-824T single nucleotide polymorphism (SNP)49 and accelerated aging/telomere length50]. Thereafter, multiple linear regression analyses were performed to determine associations between three-year %Δ in cTnT level and personality traits, independent of a priori selected covariates. These analyses were performed in Africans and Caucasians with and without considering specific coping styles. Personality Table 1. Baseline characteristics of a bi-ethnic South African cohort Variables Africans (n = 155) Caucasians (n = 181) p-value Cohen’s d φ-value Demographic factors Age (years) 44.25 ± 7.40 46.46 ± 9.95 0.023 –0.25 Men, n (%) 79 (50.97) 88 (48.62) 0.931 0.02 Women, n (%) 76 (49.03) 93 (51.38) 0.668 0.02 Lifestyle and biochemical measurements Cotinine (ng/ml) 26.11 ± 60.52 24.72 ± 82.03 0.861 0.02 GGT (U/l) 42.94 (27.67–74.54) 18.00 (12.00–30.00) < 0.001 0.63 Waist circumference (cm) 92.90 ± 14.86 93.43 ± 16.18 0.754 –0.03 Physical activity (kcal/day) 2584.94 (2156.28–3118.10) 2966.95 (2384.84–3528.59) 0.002 –0.35 Total cholesterol:HDL cholesterol 4.01 (3.22–5.03) 4.79 (3.67–6.25) 0.002 –0.35 HbA1c (measured as %) 5.70 (5.50–6.20) 5.50 (5.20–5.70) < 0.001 0.63 Oestradiol (pmol/l) 101.30 (65.75–164.300) 79.13 (45.68–135.30) 0.286 0.12 Coping scores Defensive coping 28.28 ± 4.13 28.93 ± 3.87 0.134 –0.16 Defensive coping ≥ 31, n (%) 61 (39.35) 78 (43.09) 0.488 0.03 Seeking social support coping 25.82 ± 4.88 18.79 ± 4.91 < 0.001 1.44 Seeking social support coping ≥ 28, n (%) 61 (39.35) 8 (4.42) < 0.001 0.43 Avoidance coping 21.34 ± 3.74 23.70 ± 5.12 < 0.001 –0.52 Avoidance coping ≥ 23, n (%) 55 (35.48) 105 (58.01) < 0.001 0.23 Personality trait scores Extraversion 43.26 ± 7.62 44.64 ± 6.64 0.077 –0.19 Neuroticism 32.54 ± 9.30 29.30 ± 8.70 0.001 0.36 Conscientiousness 44.90 ± 7.87 47.87 ± 6.70 < 0.001 –0.40 Openness to experience 44.96 ± 7.32 44.92 ± 6.63 0.966 0.01 Agreeableness 52.83 ± 6.45 52.29 ± 5.59 0.833 0.09 Cardiac risk markers cTnT (pg/ml) 4.14 (2.99–5.42) 4.87 (3.19–7.03) 0.001 –0.37 cTnT ≥ 4.2 pg/ml, n (%) 73 (47.71) 111 (61.67) 0.011 0.14 cTnT ≥ 5.6 pg/ml, n (%) 33 (21.57) 70 (38.89) 0.001 0.19 NT-proBNP (pg/ml) 28.88 (16.61–51.61) 34.86 (20.83–55.28) 0.591 –0.06 Haemodynamic measurements 24-h SBP (mmHg) 131 ± 14.53 125 ± 12.52 < 0.001 0.50 24-h DBP (mmHg) 83 ± 10.03 77 ± 8.16 < 0.001 0.65 24-h hypertension, n (%) 100 (64.52) 78 (43.09) < 0.001 0.21 Medication Anti-hypertensive drugs, n (%) 51 (32.90) 23 (12.71) < 0.001 0.24 Thiazides, n (%) 19 (12.26) 9 (4.97) 0.016 0.13 ACE inhibitor, n (%) 18 (11.61) 4 (2.21) 0.001 0.19 Diabetes medication, n (%) 9 (5.81) 2 (1.10) 0.016 0.13 Results of t-tests of independent groups are displayed as arithmetic mean ± standard deviation or as median (interquartile range) for variables that were not normally distributed. Chi-squared (χ2) tests were used to determine proportions and prevalence and are indicated as frequencies (%). GGT, gamma glutamyl transferase; total cholesterol:HDL cholesterol, total cholesterol to high density lipoprotein cholesterol ratio; HbA1c, haemoglobin A1c; cTnT, cardiac troponin T; NT-proBNP, N-terminal pro-brain natriuretic peptide; SBP, systolic blood pressure; DBP, diastolic blood pressure; ACE, angiotensin converting enzyme. Effect sizes are indicated by Cohen’s d or φ-values. Cohen’s d for independent t-tests: 0.2 = small effect, 0.5 = medium effect and 0.8 = large effect. φ-values for chi-squared tests: 0.1 = small effect, 0.3 = medium effect and 0.5 = large effect.
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