published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

While obstructive sleep apnea among children with Down syndrome is very common, the pre-existing risk factors and its impact to neurodevelopment are not well known. The aims and objectives of this systematic review are to determine the prevalence of OSA among DS children and to identify the associated risk factors. 6 articles that met the inclusion criteria were retrieved after using PubMed and Google Scholar in literature searching. The prevalence of OSA has great variation among different countries but are relatively high, ranging from 57% to 79%. OSA was significant associated with obesity, age and tonsil size. It is also known to associate with behavioral problem in DS children and delay their neurodevelopment. Therefore, early treatment followed by appropriate modification in lifestyle and diet is crucial in managing OSA. / published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Dentistry / Master / Master of Orthodontics

Doctor of Philosophy (Medicine) / Sleepiness is an important source of morbidity in the community, with potentially catastrophic consequences of occupational or driving injuries or accidents. Although many measures of sleepiness exist, there is no gold standard. The electroencephalograph (EEG) has been studied as an indicator of sleep pressure in the waking organism, or sleep depth. A mathematical model has been developed, relating the observed EEG to interactions between groups of neurons in the cortex and thalamus (Robinson, Rennie, Rowe, O'Connor, & Gordon, 2005; Robinson, Rennie, & Wright, 1997). These interactions are thought to be important in the transition from wake to sleep. Sleepiness is common in obstructive sleep apnea (OSA). The measurement of sleepiness would have great utility in quantifying the disease burden, measuring treatment response, or determining fitness for work or driving. This study will evaluate parameters derived from the EEG mathematical model as a measure of sleepiness. It is divided into the following four parts: 1. Subjects with likely OSA based on symptoms and demographics from an international database were compared with matched non-OSA controls. The OSA group showed deficits in executive function and abnormalities on evoked response potential testing. 2. Outcomes from a cross-sectional study in a sleep-clinic OSA population were aggregated by factor analysis into a five summary variables relevant to sleepiness: subjective sleepiness, mood & anxiety, memory & learning, driving, and executive functioning. 3. EEG mathematical model parameters from wake EEG recordings were related to the five summary outcomes. Executive function correlated with a parameter Z, representing the negative feedback loop between the thalamic reticular nucleus and the thalamocortical relay nuclei. 4. EEG model parameters during first NREM sleep cycle of 8 subjects with regular sleep architecture were studied. Net cortical excitation (parameter X) is predicted to increase across the cycle, while there was, as predicted, a greater inhibitory effect of the thalamic reticular nucleus upon thalamocortical relay cells (parameter Z). In this preliminary assessment, EEG model parameters reflecting thalamocortical interactions are sensitive to prefrontal lobe tasks such as executive function, which are known to be vulnerable to sleep loss and sleepiness, and these parameters also show variation with increasing sleep depth.

Laboratory and field studies have consistantly shown that sleep loss negatively impacts on neurobehavioural performance and alertness. Moreover, recent research suggests that the detrimental effects of sleep loss are qualitatively and quantitatively similar to the effects of alcohol intoxication. Despite this, sleepiness-related performance impairment has not been subject to the strict levels of regulatory intervention that govern alcohol consumption when driving and/or at work. It has been proposed that this failure to address the occupational, health and safety impact of sleep loss, and the subsequent lack of legislation to manage and control sleepiness in a manner commensurate with the associated statistical risks, may in part, reflect a failure to provide policy makers with a readily understood index of the relative risk associated with sleep loss. Therefore the aim of the studies in this thesis was to assess and quantify the effects of sleep loss on a range of measures, including neurobehavioural performance, sleepiness, and daytime sleep quality and quantity.

Thesis (Ph. D.)--University of Sydney, 1998. / Title from title screen (viewed Apr. 15, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Dept. of Respiratory Medicine, Royal North Shore Hospital, Faculty of Medicine. Degree awarded 1998; thesis submitted 1997. Includes bibliography. Also available in print form.

Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 83-91).

Thesis (Ph. D.)--Virginia Commonwealth University, 2008. / Prepared for: Center for Public Policy. Bibliography: leaves 72-76. Also available online via the Internet.

Thesis (M.Med.Sc.)--University of Hong Kong, 2004. / Also available in print.

Thesis Ph.D. - University of Queensland, 2005. / Includes bibliographical references.