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    Obstructive sleep apnoea in Aotearoa/New Zealand : an objective and questionnaire-based approach to population prevalence and clinical screening : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Public Health at Massey University, Wellington Campus, New Zealand
    (Massey University, 2004) Mihaere, Kara
    The goals of this thesis were to objectively assess the prevalence of obstructive sleep apnoea syndrome (OSAS) among Māori and non-Māori adults in a community-based sample, and to develop a questionnaire-based multivariate predictive tool for OSAS, to help improve referral of patients to specialist sleep services, and prioritise waiting lists. This research was situated within the wider scope of ethnic inequalities in health between Māori and non-Māori, and was conducted within a Kaupapa Māori Research (KMR) framework. Between August 1999 and June 2001 letters and information were progressively sent out to 1200 (600 Māori, 600 non-Māori) Wellington residents aged 30-60 years selected randomly from the electoral rolls. Participants were asked to wear a small sleep monitoring device (MESAM4) for one night in their own homes and to fill out a sleep questionnaire. Contemporaneously, sleep and questionnaire data were collected from 510 consecutive patients aged 30-60 years, who were referred to the regional sleep clinic for suspected OSAS. In the community sample, OSA was found to be more prevalent among Māori. Among men, 21.98% of Māori had OSA (RDI≥ 5) compared with 11.37% of non-Māori. Among women, 6.28% of Māori and 3.02% of non-Māori respectively had OSA (RDI≥ 5). The higher risk among Māori appeared to be due to well-recognised risk factors such as higher body mass index (BMI) and larger neck circumference, rather than ethnicity per se. Using the combined data from the community and clinical samples, two clinical prediction models were developed using logistic regression modelling. One model (Model 1a) included age, sex, observed apnoeas, self-reported habitual snoring, subjective excessive daytime sleepiness, and BMI. The second model (Model 2a) included neck circumference instead of BMI. Model 1a correctly classified 82.50% of participants (sensitivity 72%, specificity 87%). Model 2a correctly classified 81.10% of participants (sensitivity 80%, specificity 82%). This research indicates that OSA is a common problem among New Zealand adults and that ethnic disparities exist. The results provide important guidance for planning to meet population needs, by identifying differential needs of specific groups. The prediction models provided reliable estimates of a priori probability of OSA, and therefore may be useful tools for screening patients for OSAS.
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    Positive airway pressure for obstructive sleep apnoea : systematic evaluation versus clinical and technological drift : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Public Health at Massey University, Wellington Campus, New Zealand
    (Massey University, 2005) Marshall, Nathaniel Stuart
    The practice of sleep medicine is expanding and evolving rapidly, often ahead of the evidence base to support clinical practice. Obstructive Sleep Disordered Breathing (SDB) is a condition characterised by repetitive airway collapse causing harmful intermittent blood oxygen desaturations and fragmented sleep. When combined with daytime sleepiness it is known as Obstructive Sleep Apnoea Syndrome (OSAS). Continuous Positive Airway Pressure (CPAP) eliminates SDB by pneumatically splinting open the airway with positive air pressure applied through the nose and/or mouth. CPAP effectively reduces daytime sleepiness in patients with severe OSAS. However, doubt remains as to the effectiveness of CPAP in the majority of patients with mild-moderate OSAS. The effects of CPAP were compared to a placebo CPAP during a three week crossover Randomised Controlled Trial (RCT) that included 31 mild-moderate OSAS patients. CPAP effectively eliminated SDB (when worn) and moderately improved subjective sleepiness. But. it did not improve objective wakefulness, mood, psychomotor function, or quality of life. Patients who were extremely sleepy at baseline tended to gain the most placebo adjusted benefit from treatment. A systematic review and meta-analysis aimed to gather and objectively combine all relevant RCT studies to find our whether CPAP reduced sleepiness in patients with mild-moderate OSAS. Seven trials were combined and showed that both subjective sleepiness and objective wakefulness were slightly improved by CPAP therapy. Objective sleepiness was not improved by CPAP. It is not clear from these two studies that treating mild-moderate OSAS with CPAP is an effective use of resources. CPAP effectiveness might be limited by sub-optimal compliance. C-Flex aims to improve compliance by modulating pressure during exhalation. C-Flex was compared to CPAP during a pilot RCT that included 19 patients with severe OSAS. C-Flex was associated with a non-significant increase in compliance of 1.7 hours/night compared to CPAP. However, this increase in compliance was not associated with better daytime patient outcomes. Further experiments are proposed as a result of our pilot RCT. This thesis helps expand evidence-based sleep medicine. Practitioners need to be vigilant, ensuring that treatments are effective in the patients groups in which they are being used (clinical drift), and that new treatments are not adopted without superiority over existing treatments (technological drift).