Severe asthma, chronic obstructive pulmonary disease (COPD) and bronchiectasis are well-recognised public health priorities by the World Health Organisation. People affected by these obstructive airway diseases (OAD) can suffer from considerable impairment in their quality of life due to the high burden of symptoms, exacerbations/lung attacks, and associated morbidity. All of these shared characteristics may also be detrimental to the person’s ability to carry out activities of daily life, and are likely to lead to a vicious circle of physical activity reduction and deconditioning that will impair health-related quality of life. In the general population, engaging in healthy levels of physical activity and reducing sedentary time have been regarded as highly beneficial in the prevention and treatment of several chronic diseases. In COPD, the impairment in these behaviours has been widely characterised and the importance of addressing them as part of disease management is recognised and accepted. However, in severe asthma and bronchiectasis, the characterisation of physical activity and sedentary time and the role of optimising these behaviours in disease management is largely under-researched. In this Thesis, I characterise the degree of physical activity levels and sedentary time in a severe asthma population and examined whether the activity levels were comparable to that found in moderate to severe COPD and bronchiectasis. I also investigated the associations between physical activity levels, pulmonary and extrapulmonary characteristics, and health-related quality of life in these diseases. In my studies I found that compared to people without respiratory diseases, people with severe asthma engage in lower levels of moderate and vigorous intensity physical activity but similar levels of sedentary time. Better parameters in both behaviours were associated with better disease features, including exercise capacity, asthma control, and systemic inflammation. When comparing these results with bronchiectasis and moderate to severe COPD populations, I found that lower levels of physical activity is a shared behavioural characteristic of people with OAD, albeit to a lesser degree in severe asthma and bronchiectasis. Shared pulmonary characteristics differed between diseases but nevertheless, exercise capacity and airflow limitation explain an important proportion of physical activity levels in OAD. Finally, I demonstrate that physical activity and other extrapulmonary characteristics including skeletal muscle strength and comorbidities, are statistically and clinically associated with health-related quality of life in bronchiectasis and severe asthma. The associations were stronger for the activity and impact domain and suggest that health-related quality of life in these diseases could be improved by addressing these extrapulmonary characteristics. The findings of this Thesis have extended our knowledge of the characterisation of physical activity and sedentary time in severe asthma and bronchiectasis. Lower levels of physical activity are a prevalent feature in OAD populations and should be considered as a treatable extrapulmonary risk factor for the management of several disease outcomes not only in COPD, but also in severe asthma and bronchiectasis populations.
|Qualification||Doctor of Philosophy|
|Award date||1 May 2019|
|Publication status||Published - May 2019|