3. Electronic Theses and Dissertations (ETDs) - All submissions

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    The impact of dietary habits and practices during adolescence on the risk of obesity: the birth to twenty cohort
    (2013-04-29) Feeley, Alison Bridget Bernadette
    Background: South Africa is not exempt from the obesity epidemic and latest figures show that a third of adult men and two-thirds of adult women are either overweight or obese. Concomitant are changes in dietary habits and practices which have been implicated in the risk of obesity. Concern is that obesity and related non-communicable diseases (NCDs) manifest at younger ages. Adolescence, as well as being a stage during the life course when eating attitudes and behaviours are formed, is a particular time when the aetiology of NCDs becomes evident. Little is known about the dietary patterns during adolescence in South Africa, and if policymakers are to attempt to reduce the burgeoning statistics relating to obesity then it is important to understand adolescent dietary habits and eating practices. Aims: To describe adolescent dietary habits and practices among South African adolescents and how they might influence obesity risk. Methods: This study used a mixed methods study design, using both historical and prospective data and included four study components in both an urban (components 1-3) and a rural setting (component 4). Firstly, a cross-sectional assessment of fast-food intake of urban 17-year-olds from the Birth to Twenty Cohort (Bt20); secondly, a longitudinal descriptive analysis of dietary habits and practices of the Bt20 participants over a five-year period, between ages 13 – 17 years followed; thirdly a longitudinal assessment of the relationship between dietary habits, change in socio-economic status (SES) and obesity in the Bt20 adolescents was conducted; and finally, an exploratory survey assessing the availability of fast foods in a rural area. Results: The cross-sectional analysis showed that mean fast food intake was 8.1 (4.6) items and 7.2 (4.7) items/week for males and females respectively. Furthermore, the kota (or quarter) was the most popular fast food item and on average it provided 5 370 kJ, 51 g fat (of which 13 g Saturate fatty acids (SFA)). The longitudinal analysis showed that poor dietary habits and practices were embedded by the age of 13 years and were characterised by: high fast food consumption with at least five items/week consumed from the age of 13 years. Breakfast (weekday and weekend) consumption declined for both genders and females ate breakfast less regularly than males. Snacking while watching television increased with age: with females consuming more (4.0 (4.8) - 7.3 (5.9)) snacks per week than males (3.3 (4.5) - 6.0 (5.8). Two-thirds of participants ate their main meal with their family but among girls there was a trend towards eating this meal less regularly with increasing age. Confectionery consumption remained the same, around nine items/week for males and 10 items/week for females. Lunch box usage declined with age, conversely the number of tuck shop purchases increased with age. The prevalence of combined overweight and obesity was (8.1%) and (27%) in 17-year-old males and females respectively. In males only, soft drink consumption was associated with obesity denoted by BMI z-score and fat mass (p<0.05). In the final multivariate model, soft drink consumption remained positively and significantly associated with both outcomes and „acquiring‟ a fridge over the 12-year period remained negatively associated with both BMI z-score and fat mass (p<0.001). Among females, no associations were found. Thus further data on other lifestyle variables are needed to understand better the exposures related to obesity risk in females. In the rural setting fast food was found to be available albeit a limited variety; two-thirds of the collected samples were either vetkoek (fried dough balls) or fried chips (yielding between 943 kJ – 5 552 kJ and 11 g – 64 g fat). Compared to the kotas available in Soweto, the samples obtained in the rural setting contained more energy and fat (6 300 kJ, 60 g fat vs. 5 369 kJ, 51.5 g fat). Conclusions: This research highlights that poor dietary habits and practices prevail in adolescence which may be implicated in negative health outcomes in later life. Of concern is the finding that poor dietary habits were embedded by the age of 13 years which suggests that interventions need to target families and children prior to adolescence in order to reduce the pervasiveness of these habits in the older child. The prevalence of combined overweight and obesity is higher than the national statistics for both boys and girls at the age of 17-years. This research confirms that some dietary behaviours are associated with obesity risk namely soft drink consumption – but in males only. However soft drink consumption may be a marker for other lifestyle behaviours associated with obesity. Other dietary habits were not shown to be associated with obesity in neither males nor females, which highlights the difficulty in the measurement of exposures relating to diet. This study also showed in males at least, that socio-economic factors are important when considering obesity risk. The availability of fast foods in a relatively impoverished rural area is concerning as it may indicate that this community is undergoing nutritional changes such as those seen in urban environments. With urbanisation and economic transition, households experience a change in SES and these changes drive behaviour which can either enable or disable health outcomes. In this study SES improvement, e.g. fridge ownership seems to enable certain behaviours which can be obesogenic. However we cannot halt development in this context but we must devise ways to improve lifestyle choices which will promote health rather than impede it.
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    Mutually independent
    (2008-10-08T09:13:11Z) Morgado, Claudia Frederica
    No abstract.
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    Statistical approaches for classifying & defining areas in South Africa as "urban" or "rural"
    (2007-10-10T07:37:16Z) Laldaparsad, Sharthi
    The purpose of this research report is to utilise appropriate statistical (both non-spatial and spatial) techniques to classify areas in the country into urban and rural. These areas, as derived by means of each statistical method, are profiled and common characteristics amongst them are summarised for classification and definition of urban and rural areas. Population data for these areas were aggregated to determine the overall urbanisation for the country. The methodology utilised was that of supervised classification. Two sample data sets of areas that are known with certainty to be urban or rural were derived and used consistently throughout the study. The importance of utilising areas of known urban and rural status was firstly to identify essential patterns or predominant characteristics from areas that are known, and thereafter to apply similar characteristics to areas that are not known or are ambiguous, in order to classify them as either urban or rural. Sample 1 comprises all areas in the country with formal and informal urban settlements, as well as formal rural areas, i.e. farms. Sample 2 is similar to sample 1, but in addition it includes areas falling under the jurisdiction of traditional authorities, known as tribal areas, which were classed as known rural. Non-spatial techniques, namely linear logistic regression, classification trees and discriminant analysis, as well as spatial techniques, namely straight-majority-rule and iterated conditional modes (ICM), were researched, applied and analysed for both samples, for each province and for South Africa as a whole, using the 2001 South African population census data. Comparisons were made with the 1996 census information. All three non-spatial statistical methods gave insight into those census variables and their combinations that best describe the subject under research, i.e. urban and rural. All three methods identified significant variables that clearly separate urban and rural areas. The results of all three non-spatial statistical methods showed similarities within each sample, but differences were noted between the two samples. All three nonspatial statistical methods applied to sample 1 classified the majority of the tribal EAs (Enumeration Areas) as urban, whilst the results from sample 2 are very similar to those obtained from both censuses, since both censuses and sample 2 predefine tribal settlements as rural.
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    Causes of and trends in childhood mortality in a rural South African sub-district
    (2006-10-31T13:53:45Z) Ansong, Daniel
    Background: Studies into childhood mortality present the opportunity to identify the leading and common causes of childhood mortality in different populations. Objectives: To study the trends in all-cause mortality, and patterns of cause-specific mortality, in children 0-14 years living in the Agincourt sub-district of South Africa over the period 1992-2000. Methods: Secondary data analysis based on the longitudinal database from the Agincourt Demographic and Health Surveillance System was used to study trends in childhood mortality between 1992 and 2000, and a comparison was made between the earlier period (1992-96) and the later period (1997-2000). Results: Seven hundred and twenty four deaths occurred over the 9 year period, 1992 to 2000, in children aged 0-14 years in the Agincourt sub-district of South Africa. Over 80% of the deaths occurred in children under-five years of age. Death rates in children under one year in the periods 1992-1996 and 1997-2000 were 8.9/1000 live births and 18.0/1000 live births respectively. Children under five years between 1992-1996 and 1997-2000 had death rates of 18.0/1000 live births and 35.0/1000 live births respectively. There was a statistically significant difference in death rate in infants, and in children less than five years, in those who died over the period 1992-1996 and those who died during the later period 1997-2000, with mortality showing an increasing trend (p-values <0.0001 for infants and for children under five years). Overall mortality rates in all children under 14 years between 1992-1996 and 1997-2000 were 26.4/10000 person-years and 37.7/10000 person-years respectively. There was no significant statistical difference in the overall mortality trend among children aged 0-14 years between the two periods of time (p-value 0.614). Infectious and communicable diseases were the leading causes of death with diarrhoeal deaths accounting for 15.2%, HIV/AIDS 9.7% and malnutrition 7.6%. Deaths from diarrhoeal disease between 1992-1996 and 1997-2000 were 481/million and 449/million person-years respectively. Deaths from HIV/AIDS within the same time periods were 107/million and 607/million person-years respectively. HIV/AIDS showed a statistically significant difference over the two periods with an increased risk ratio of 5.59 (95% confidence interval of 4.6 to 70). Conclusion: This analysis reinforced previous findings pointing to the fact that infectious and communicable diseases are the leading causes of childhood mortality in South Africa and other developing countries. HIV/AIDS and diarrhoeal diseases have emerged as major causes of mortality in this analysis. Efforts to control the HIV epidemic and prevent the spread of HIV/AIDS must be accelerated in the Agincourt sub-district.
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