Motivation -
Depression is a mental disorder that has been associated with cardiovascular morbidity and
mortality in the Western world. Cardiometablic 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 cardiometabolic risk. We therefore aimed to assess cardiometabolic 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). Cardiometabolic 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 cardiometabolic 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 cardiometabolic 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
cardiometabolic function including cardiovascular dysfunction. Markers of cardiometabolic
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 cardiometabolic 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 hypercoagulation 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 hypercoagulation may partially be the mediating factor between
depressive symptoms and cardiovascular risk in African men; a situation that may be
exacerbated by hyperkinetic blood pressure.
In conclusion, through the assessement of cardiometabolic function and neuroendocrine
responses, it seems that Africans withdepressive symptoms are at great risk for
cardiovascular related morbidity and mortality, this was particulary evident in the African
men (Manuscript 1 and 3). Additionally, it appears that blunted neuroendocrine responses and
hypercoagulation could be seen as possible cardiovascular risk markers in Africans with
depressive symptoms. / PhD (Physiology), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/11842 |
| Date | January 2014 |
| Creators | Mashele, Nyiko |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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