CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 4, July/August 2022 176 AFRICA study were more physically active than the Africans. There is a possibility that the combination of high conscientiousness but low neuroticism in Caucasians could have contributed to the chosen lifestyle choice, with beneficial effect for their emotional well-being and cardiac health.59-62 The engagement in physical activity has been shown to buffer prolonged emotional stress by enhancing self-esteem and feelings of competence, and appraising stressors as less threatening.62 Besides buffering the detrimental downstream cardiovascular effects of the stress response, physical activity has also been related to nitric oxide-mediated vasodilation, reduced blood pressure and suppression of atherogenesis.61 However, in both Africans and Caucasians, physical activity was not associated with cardiac injury, nor was it associated with certain BTI traits or the use of specific coping strategies. Our findings may also be partially explained by looking at the role of conscientiousness and neuroticism in the brain–stress circuitry. Indeed, these traits are dependent on the integrity of the dorsolateral prefrontal cortex (DLPC).63 This region is very important for decision making, problem solving and top-down regulation of emotion and behaviour,64,65 therefore forming an integral part of DefS success. During an in-control DefS stress response, the DLPC can suppress activity in the anterior cingulate cortex and decrease activity in subcortical areas such as the amygdala.65 Higher conscientiousness has been associated with greater activity in this area.63 However, a loss of DLPC integrity was associated with higher scores in neuroticism, but lower scores in conscientiousness.63 Individuals scoring high in neuroticism tend to experience psychological stress as uncontrollable and threatening, resulting in greater emotional reactivity upon stress exposure,66,67 which is also characteristic of avoidance coping.14,52 In fact, uncontrollable stress has been found to weaken the connectivity between the DLPC and the anterior cingulate cortex, which increases activity in the amygdala.65 Indeed, increased amygdalar drive towards the prefrontal cortex (bottom-up regulation) during stress exposure may also decrease the conscientious-based cognitive processes that accompany DefS, resulting in more emotion-focused avoidance coping.68 A change in the threshold for effective DefS may emerge, which can sensitise future stress DefS responsiveness, with detrimental effect on cardiac health. As a result, increased input from the central nucleus of the amygdala may exaggerate sympathetic activity in the cardiovascular system, and which may contribute to higher cTnT levels. Neuroticism may prevent effective DefS,55 and this notion corresponds with our findings in Africans, where Defs was inversely related to neuroticism scores. The potential of DLPC integrity loss induced by ineffective DefSmight therefore increase. Additionally, neuroticism did not associate positively with cTnT levels over time in the Africans who utilised DefS, whereas in the Caucasians, neuroticism, together with conscientiousness were associated with a lower likelihood to predict a hypertensionrelated cTnT cut-off point. Conscientiousness may thus contribute to better DefS and decrease the greater emotional reactivity that usually accompanies neuroticism and avoidance coping. This may hold true as both Africans and Caucasians had conscientiousness scores that were considered average according to the BTI.24,37 Although Africans scored higher in neuroticism than the Caucasians, the scores of both races were still considered low according to the BTI.24,37 Therefore, the greater conscientiousness scores in both races may contribute to greater activity in the DLPC, which could suppress activity in subcortical areas such as the amygdala for a more controlled stress response. Limitations and recommendations The data presented stem from a relatively small cohort and conclusions can therefore not be generalised to the entire South African population. Investigation of study aims must therefore be expanded to other cohorts in South Africa. More expanded personality inventories such as the revised NEO personality inventory (NEO PI-R) may be incorporated to gain greater insight regarding the different facets of personality traits. It is recommended that information be obtained on the serotonin transporter gene SNP, 5-HTTLPR, which has been related to higher neuroticism.29,57 The SABPA design also did not meet the requirements of a behavioural genetic study, which requires information about family, twins and adopted children. Because both the BTI and NEO PI-R are self-report questionnaires, next-generation sequencing will advance the analysis and interpretation of the relationships between genes and personality traits. Conclusion In both Africans and Caucasians, scoring high in DefS and avoidance coping, respectively, have previously been associated with greater emotional vascular hyper-responsiveness and subsequent risk of cardiac ischaemia. Greater emotional reactivity is usually associated with higher scores in neuroticism. However, in the current study, higher conscientiousness reflected healthier stress coping responses and improved cardiac health. We are grateful to all the participants who volunteered to participate in the SABPA study, as well as for in-kind analyses from collaborators. Funding was obtained from North-West University and the North-West Education Department of South Africa, South African Medical Research Council, National Research Foundation, ROCHE Diagnostics, Heart and Stroke Foundation South Africa (HSFSA2019/01) and the Metabolic Syndrome Institute, France. Any opinion, findings and conclusions or recommendations expressed in this material are those of the author(s) and therefore funding bodies do not accept any liability in regard thereto. References 1. Dimsdale JE. Psychological stress and cardiovascular disease. J Am Coll Cardiol 2008; 51(13): 1237–1246. 2. De Kock A, Malan L, Hamer M, Malan N. Defensive coping and subclinical vascular disease risk–associations with autonomic exhaustion in Africans and Caucasians: the SABPA study. Atherosclerosis 2012; 225(2): 438–443. 3. Malan L, Malan NT. Emotional stress as a risk for hypertension in sub-Saharan Africans: are we ignoring the odds? In: Islam MS (ed). Hypertension: From Basic Research to Clinical Practice. Advances in Experimental Medicine and Biology. New York: Springer International, 2017: 497–510. 4. Malan L, Hamer M, Von Känel R, Lambert GW, Delport R, Steyn HS, et al. Chronic defensiveness and neuroendocrine dysfunction reflect a novel cardiac troponin T cut point: the SABPA study.
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