Abstract
Obstructive sleep apnoea (OSA) is a serious form of sleep-disordered breathing (SDB). OSA is associated with cardiovascular disease, compromises driving safety and increases the risk of peri-surgery complications. Reports suggest that many people with OSA, even those with obesity, remain undiagnosed. Adherence to the treatment of continuous positive airway pressure can be poor. Emerging research points towards an inverse association between physical activity and severity of SDB. Therefore, the work in this thesis involved various studies relevant to the role of physical activity in the diagnosis and treatment of OSA.In the diagnostic pathway, the first study examined the association between self-reported slow-walking speed (an indicator of frailty) and SDB in the large, cross-sectional Multi-Ethnic Study of Atherosclerosis (MESA). The 95% CI risk differences (multivariable-adjusted) for slow vs. faster walking speed were: sleep apnoea (0.4-2.5%), self-reported apnoeas (0.1-3.8%), loud snoring (1.2-8.3%), and daytime sleepiness (3.0-7.8%). The multivariable-adjusted risk ratio indicated that slower walkers had 1.5 (95%CI: 1.0 to 2.1) times the risk of sleep apnoea vs. faster walkers.
In a second study, which involved weight-loss surgery patients, the body mass index (BMI) item of the STOP-Bang screening tool was replaced with a slow-walking speed item and improved the area under the receiver operating characteristic curve for OSA screening from 0.64 to 0.70. A slower walking speed was also reported significantly more in OSA patients than non-OSA patients (% difference, 95% CI: 21.7%, 4.2-36.5%). This prevalence difference was larger than those observed for any of the STOPANG items. From these studies, it was concluded that a slow-walking speed question might help consolidate screening for OSA.
The first study in the treatment pathway of the thesis was a critical analysis of published evidence syntheses on exercise as a treatment for the symptoms of OSA. It was concluded that, despite some variability between reviews, especially in meta-analyses (mean AHI reductions between 4.66 and 17.23 events/h reported in RCT-only meta-analyses), exercise has a clinically meaningful effect on reducing OSA severity and daytime sleepiness in adults, independent of BMI changes.
In the context of OSA consequences, the second study conducted in the treatment pathway assessed whether percentage flow-mediated dilation (FMD%), an early indicator of atherosclerosis, is affected by OSA. Using the MESA dataset, it was found that the sex, race and age-adjusted mean FMD% was 0.6% lower in participants with physician-diagnosed sleep apnoea compared to undiagnosed participants. However, this mean difference was 0.3% and not statistically significant when the confounding influence of initial artery diameter was allometrically adjusted for. It was therefore concluded that people with OSA do not demonstrate a clinically important reduction in FMD%. Consequently, this outcome was not included in the final protocol phase of the thesis.
The final chapter in this thesis presents a protocol for a feasibility study examining the benefits of exercise for obese people with OSA who undergo weight-loss surgery. This 12-week aerobic and resistance training protocol was patient-informed and focused on feasibility, safety and acceptability outcomes to inform the design of a subsequent definitive randomised controlled trial. Future work should progress this protocol into the next research phase to support the optimisation of the clinical pathway for weight-loss surgery patients with OSA.
| Date of Award | 18 Oct 2019 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Greg Atkinson (Supervisor) |