Depressive symptoms and cardiometabolic health in urban black Africans : the SABPA study
Motivation - Depression is a mental disorder that has been associated with cardiovascular morbidity and mortality in the Western world. Cardio-metabolic mechanisms have been implicated as possible intermediating factors in the relationship between depressive symptoms and cardiovascular disease; however this has not yet been determined in black Africans (hereafter referred to as Africans). Aim - The overarching aim of this study was to investigate the relationship between depressive symptoms and cardio-metabolic risk. We therefore aimed to assess cardio-metabolic function, neuroendocrine responses, inflammatory and haemostatic markers in Africans with depressive symptoms compared to those without symptoms of depression. Methodology - Manuscripts presented in Chapter 2, 3 and 4 utilised data from the cross-sectional, target population multi-disciplinary “Sympathetic activity and Ambulatory Blood Pressure in Africans' (SABPA) study. The participants comprised of 200 African teachers from the Dr Kenneth Kaunda District in North-West province, South Africa. As cardiovascular disease is compromised by a positive HIV status, 19 participants were excluded from further statistical analysis. Stratification was based on the Patient Health Questionnaire 9-item (PHQ-9), which has been validated in a sub-Saharan African setting. PHQ-9 scores > 10 were used to classify participants as having signs of depressive symptoms. Subjects were further stratified by gender (Manuscript 1 and 3) and cortisol responses (Manuscript 2). Cardio-metabolic health measures included 24-hour blood pressure, metabolic syndrome markers, neuroendocrine markers [cortisol and 3-methoxy-4-hydroxy-phenylglycol (MHPG)], left ventricular hypertrophy (LVH), inflammatory and haemostatic markers (fibrinogen, C-reactive protein, plasminogen activator inhibitor-1 and D-dimer). Resting 12-lead ECG Cornell Product-Left ventricular hypertrophy (CP-LVH) was measured as a marker of target end-organ damage and cardiovascular dysfunction (Manuscript 1 and 2). Means and prevalence were computed through t-test and Chi-square analysis respectively. Significant differences of mean cardio-metabolic measures between depressive symptom status groups were also determined by analysis of covariance (adjusted for traditional cardiovascular risk factors and additional factors as specific per manuscript). Multivariate analysis was used to demonstrate associations between left ventricular hypertrophy (LVH) and cardio-metabolic markers in Africans with depressive symptoms (Manuscript 1 and 2) and a logistic regression analysis were performed to examine the association between depressive symptoms and inflammatory/haemostatic factors (Manuscript 3). All subjects who participated gave informed consent, the study was approved by the Ethics Committee of North-West University (NWU-0003607S6), in accordance with the principles outlined by the World Medical Association Declaration of Helsinki of 1975 (revised 2008). Results and conclusions of the individual manuscripts - The aim of the study was to investigate the associations between depressive symptoms and cardio-metabolic function including cardiovascular dysfunction. Markers of cardio-metabolic function assessed were 24 hour blood pressure measurements, metabolic syndrome markers, neuroendocrine markers [cortisol and 3-methoxy-4-hydroxy-phenylglycol (MHPG)], inflammatory and haemostatic variables (fibrinogen, C-reactive protein, plasminogen activator inhibitor-1 and D-dimer). Manuscript 1, focused on LVH as a marker of cardiovascular dysfunction and metabolic syndrome components as markers of cardio-metabolic function. The aim of the study was to assess the associations between LVH and metabolic syndrome (MetS) risk markers in participants with and without depressive symptoms. Results revealed that in African men with depressive symptoms the most significant determinants of LVH were systolic blood pressure (SBP) and the percentage glycosylated haemoglobin (HbA1c). While in African women (with depressive symptoms), this association was determined by low high-density lipoprotein (HDL-cholesterol). The study concluded that in black African men, independent of depressive symptoms, cardiometabolic factors (namely SBP and HbA1c) may be the driving significant factors in the development of cardiovascular diseases. Furthermore, the data showed that depressive symptoms in African women were associated with a measure of target end organ damage, and that this association was driven by a metabolic factor. Manuscript 2, the aim of this manuscript was to examine the relationship between depressive symptoms, neuroendocrine responses [with cortisol and 3-methoxy-phenylglycol (MHPG) as markers] and cardiovascular risk, i.e. LVH. The results revealed that Africans with depressive symptoms demonstrated blunted cortisol and MHPG levels in response to acute mental stress, in comparison to those without symptoms of depression. Additionally, these low cortisol and blunted MHPG responses were associated with LVH in this ethnic group. The conclusion for this manuscript was that, blunted neuroendocrine responses linked depressive symptoms and ECG left ventricular hypertrophy in Africans. When coupled to their hypertensive status, these vasoconstrictive responses (cortisol and MHPG) may underpin the increased long-term depression and vascular disease risk in urban Africans. Manuscript 3, the aim of this manuscript was to investigate the relationship between depressive symptoms and inflammatory/haemostatic markers in a cohort of urban-dwelling black African men and women. Our data demonstrated hyper coagulation vulnerability in African men with depressive symptoms. The African men with signs of depression displayed higher plasminogen activator inhibitor (PAI-1) levels and marginally elevated D-dimer levels. It was concluded that hyper coagulation may partially be the mediating factor between depressive symptoms and cardiovascular risk in African men; a situation that may be exacerbated by hyper kinetic blood pressure. In conclusion, through the assessment of cardio-metabolic function and neuroendocrine responses, it seems that Africans with depressive symptoms are at great risk for cardiovascular related morbidity and mortality, this was particularly evident in the African men (Manuscript 1 and 3). Additionally, it appears that blunted neuroendocrine responses and hyper-coagulation could be seen as possible cardiovascular risk markers in Africans with depressive symptoms.
- Health Sciences