Psychological well-being and cardiovascular function in obese African women : the POWIRS study
Motivation: Abdominal obesity (hereafter referred to as "obesity") is becoming the biggest "global epidemic" of our modern times. It is associated with a range of diseases, including cardiovascular diseases and hypertension. Recent research showed that an increase in sympathetic activity is of central importance in the pathogenesis of obesity-related diseases. Increased leptin levels and impaired baroreflex sensitivity have both been independently associated with abdominal obesity and increased sympathetic activity. A perception of poorer health may also contribute to the physiological characteristics of obesity-related diseases. A lack of data regarding sympathetic activity, leptin levels, baroreflex sensitivity and perception of health in Africans, serves as a motivation for conducting this study. Objective: To investigate the contributions of leptin levels, baroreflex sensitivity and perception of health data to increased sympathetic activity in lean and obese African women from South Africa. Methodology: The manuscript presented in Chapter 2 made use of the data obtained in the POWIRS (Profiles of Obese Women with the Insulin Resistance Syndrome) study. A group of 102 urbanized African women, living in the North-West Province of South Africa, was recruited according to body mass indexes. Only 85 subjects were included for analysis due to incomplete datasets. For this study, subjects were divided into lean and obese groups according to their waist circumferences. Anthropometric measurements were done according to standardized methods. Resting cardiovascular measurements were obtained from Finometer observations. Resting, fasting levels of leptin were calculated after radioimmunoassay analyses. Subjective perception of health was determined by means of the 28-item General Health Questionnaire. Comparisons between the groups were done using analysis of covariance (ANCOVA) whilst adjusting for cardiovascular risk factors (age. smoking, alcohol consumption and physical activity). Correlation coefficients were determined to indicate any associations between leptin, baroreflex sensitivity and perception of health with sympathetic activity (represented by heart rate) and other cardiovascular variables. The study was approved by the Ethics committee of the North-West University and all the subjects gave informed consent in writing. The reader is referred to the Methods section in Chapter 2 for a more detailed description of the subjects, study design and analytical procedures used in this dissertation. Results and conclusion: Results from this study indicate that obese African women, compared to lean African women, were older, reported higher physical activity, and exhibited higher diastolic and mean blood pressure, heart rate, cardiac output, arterial compliance, leptin and hypertension prevalence rate values. In lean African women social dysfunction was positively associated with diastolic and mean blood pressure and arterial resistance, and negatively with arterial compliance. In obese African women baroreflex sensitivity was negatively associated with diastolic blood pressure, which could be an indication of impaired baroreflex sensitivity. In this obese group a perception of social dysfunction was associated with decreased heart rate. Although leptin and heart rate were significantly higher in the obese Africans, no significant correlations existed between these variables to reflect leptin's enhancement of sympathetic activity. However, leptin correlated weakly but positively with cardiac output (p = 0.054, r = 0.32). In conclusion, baroreflex sensitivity (although similar between groups) and leptin seem to contribute to blood pressure and thus hypertension in obese African women, possibly through increased sympathetic activity and volume loading. A perception of poorer health, especially a perception of social dysfunction, could possibly contribute to this image.
- Health Sciences