Physical activity and sedentary behaviour across the spectrum of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) patients are generally more sedentary and less physically active than healthy adults; putting them at increased risk of hospitalisation and death. For patients with mild-moderate COPD, physical activity appears to be reduced compared with apparently healthy adults but differences in time spent sedentary are less well established. Additionally, there is a need for a greater understanding of the correlates of behaviour in mild-moderate patients with much of the existing literature focusing on more severe or mixed stage patient samples and with many studies lacking objective behavioural monitoring, not adjusting for confounders and a paucity of data on correlates of sedentary time. Despite having mild-moderate airflow obstruction, these patients also report a range of symptom burdens with some individuals reporting severe symptoms. Subsequently, these patients represent a sub-set of individuals who may require lifestyle interventions. Therefore, factors associated with patients reporting more severe symptoms need to be identified to help understand how this phenomenon may manifest and be intervened upon. For patients with more advanced COPD who are admitted to hospital for an acute exacerbation behavioural intervention focussing on less intense movement may be a more suitable approach for reducing the risk of readmissions than more intense physical activity or exercise. To date no studies have specifically targeted reductions in sedentary behaviour in COPD. In addition, wearable self-monitoring technology may facilitate the provision of such interventions, removing important participation barriers such as travel and cost, but this has not been sufficiently examined in COPD. This thesis investigated: (i) objectively measured physical activity and sedentary time and the correlates of these behaviours for mild-moderate COPD patients and apparently healthy adults (Study One); (ii) factors associated with self-reported symptom severity and exacerbation history in mild-moderate COPD patients (Study Two) and (iii) the feasibility and acceptability of a home-based sedentary behaviour intervention using wearable self-monitoring technology for COPD patients following an acute exacerbation (Study Three). Methods: Study One: COPD patients were recruited from general practitioners and apparently healthy adults from community advertisements. Objectively measured moderate-to-vigorous physical activity (MVPA), light activity and sedentary time for 109 mild-moderate COPD patients and 135 apparently healthy adults were obtained by wrist-worn accelerometry. Patients with at least four valid days (≥10 waking hours) out of a possible seven were included in analysis. A range of demographic, social, symptom-based, general health and physical factors were examined in relation to physical activity and sedentary time using correlations and linear regressions controlling for confounders (age, gender, smoking status, employment status and accelerometer waking wear time). Study Two: In 107 patients recruited from general practitioners, symptoms were assessed using the COPD Assessment Test (CAT) and Modified Medical Research Council (mMRC) questionnaires. Twelve-month exacerbation history was self-reported. Exercise capacity was assessed via incremental shuttle walk test (ISWT) and self-reported usual walking speed. Physical activity and sedentary time were obtained from a wrist-worn accelerometer. Study Three: Patients were randomised in-hospital into a usual care (Control), Education or Education + Feedback group with the intervention lasting 14 days following discharge. The intervention groups received information about reducing prolonged sitting. The Education + Feedback group also received real-time feedback on their sitting time, number of stand-ups and step count at home through an inclinometer linked to a smart device app. The inclinometer also provided vibration prompts to encourage movement when the wearer had been sedentary for too long. Feasibility of recruitment (e.g. uptake and retention) and intervention delivery (e.g. fidelity) were assessed. Acceptability of the intervention technology (e.g. wear compliance, app usage and response to vibration prompts) was also examined. Results: Study One: COPD patients were more sedentary (592±90 versus 514±93 minutes per day, p 20 or an mMRC score of ≥2 had lower VMCPM, were more sedentary and took part in less light activity than patients reporting a CAT score of 0-10 or mMRC of 0, respectively. Patients reporting ≥2 exacerbations took part in less MVPA than patients reporting zero exacerbations. Study Three: Study uptake was 31.5% providing a final sample of 33 COPD patients. Retention of patients at two-week follow-up was 51.5% (n=17). Reasons for drop-out were mostly related to being unable to cope with their COPD. Patients wore the inclinometer for 11.8±2.3 days (and charged it 8.4±3.9 times) with at least one vibration prompt occurring on 9.0±3.4 days over the 14 day study period. Overall, 325 vibration prompts occurred with patients responding 106 times (32.6%). 40.6% of responses occurred within 5 minutes of the prompt with patients spending 1.4±0.8 minutes standing and 0.4±0.3 minutes walking, taking 21.2±11.0 steps. Discussion: Study One: COPD patients were less active and more sedentary than apparently healthy adults; however, factors predicting behaviour were similar between groups. Correlates differed between sedentary time, light activity and MVPA for both groups. Interventions to boost physical activity levels and reduce sedentary time should be offered to patients with mild-moderate COPD, particularly those reporting more severe breathlessness. Study Two: Worse exercise capacity, low levels of physical activity and more time spent sedentary are some of the factors associated with patients of the same severity of airflow limitation reporting differing symptom severities. These patients may benefit from both lifestyle and exercise interventions. Study Three: Recruitment and retention rates suggest a trial targeting sedentary behaviour in hospitalised COPD patients is feasible. A revised intervention, building on the successful components of the present feasibility study is justified. Conclusion: The findings from this thesis have contributed a greater understanding of physical activity and sedentary behaviour in COPD and can inform the development of tailored physical activity and sedentary behaviour interventions for patients across the grades of COPD severity.