An examination of physical activity and sedentary behaviour in people with chronic obstructive pulmonary disease
Year: 2020
Type: dissertation
Abstract: Insufficient levels of physical activity (PA), commonly referred to as ‘physical inactivity’, is a key risk factor for mortality and noncommunicable diseases such as cardiovascular disease (CVD), cancer, and diabetes [1]. PA is defined as any bodily movement produced by skeletal muscles that requires energy expenditure and encompasses exercise (planned, repetitive PA that aims to improve or maintain physical fitness), sport, and activities of daily living, work, leisure and transportation [2]. In the past two decades, there has been an increasing focus on the problem of physical inactivity in people with chronic obstructive pulmonary disease (COPD). COPD is a highly prevalent public health issue and will be the third leading cause of death worldwide by 2030 [3]. Physical inactivity is known to be more common in people with COPD compared with age-matched healthy individuals [4]. Reductions in PA occur early in the COPD disease trajectory and across all stages of disease severity, accompanied by deterioration in lung function and health status [5]. Despite consistent evidence of the detrimental health effects of physical inactivity, strategies to increase PA and subsequently improve health outcomes in people with COPD are not well established. Physical inactivity in daily life and decline in PA over time are both associated with a higher risk of mortality [6-8] and with a higher risk of COPD-related and exacerbation-related hospitalisations in people with COPD [6, 9, 10]. Although regular PA is recommended for all individuals with COPD [11], previous research has focused on exercise training in the context of pulmonary rehabilitation and there is a lack of high-quality evidence to guide the prescription of daily PA in this population. The dose and type of PA that confers long-terms health benefits, including longevity, has been examined in small clinical samples that are non-representative of the general COPD population. There is also considerable heterogeneity in the way that PA has been measured and classified, which makes it difficult to compare results across studies. Such limitations reduce the generalisability of the evidence base and subsequently, clinicians must rely on generic PA guidelines for older adults to inform PA recommendations in people with COPD. There are innate challenges in increasing PA in people with COPD. Disease-specific limitations such as dyspnoea, fatigue, reduced aerobic capacity, and use of oxygen therapy reduce the physical capability of people with COPD to engage in PA [12], particularly levels of moderate-to-vigorous intensity physical activity (MVPA), which are characterised by an energy expenditure of ≥3.0 metabolic equivalents (METs) [13]. Furthermore, a large number of studies have evaluated the effect of interventions such as exercise training and behaviour change approaches on PA, and there is limited evidence that either strategy can increase PA in people with COPD even when delivered as part of a comprehensive pulmonary rehabilitation program [14, 15]. Even in healthy individuals who meet current PA recommendations, MVPA comprises a relatively small proportion of total waking hours, with the majority of time spent in sedentary behaviour (SB) or light-intensity PA [16]. SB is defined as any waking behaviour characterised by an energy expenditure ≤1.5 METs [17], while in a sitting, reclining or lying posture, and includes activities such as television (TV) viewing, video game playing, computer use (collectively termed ‘screen time’), driving automobiles, and reading [18]. The reality that most of daily life is spent in SB has led to growing interest in the effects of SB on the risk of mortality and noncommunicable diseases over the last ten years. Although there is evidence to suggest that in the general population, 60-75 min/day of MVPA can eliminate the increased risk of mortality, CVD and cancer associated with SB [19, 20], such high levels of MVPA are unrealistic for most people with symptomatic COPD. There is also preliminary evidence that SB is associated with a higher risk of mortality [21, 22], cardiometabolic disease [23, 24] and hospitalisation [25] in the COPD population, and that targeting reductions in SB and increases in light-intensity PA may produce health benefits even if increases in MVPA are not realised [26, 27]. Laboratory-based controlled studies in populations other than COPD have shown that interrupting SB with light-intensity PA is sufficient to improve cardiometabolic risk biomarkers such as postprandial glucose and insulin responses [28-34], and to a lesser extent triglycerides and cholesterol [34, 35]. An alternative approach of reducing time in SB and increasing participation in light-intensity PA may therefore act as a feasible intermediate goal for people with COPD, and may lead better engagement with higher intensity PA in the future [36]. However, SB has not yet been characterised in people with COPD using thigh-worn accelerometry, which is able to directly quantify posture and capture the patterns in which SB is accumulated [37]. Strategies capable of reducing the time spent in SB in people with COPD are unknown. The series of studies contained in this thesis explored the characteristics of PA and SB in people with COPD, and the effects of changing the volume and patterns of PA and SB on health outcomes. Thus the aims of the body of work contained in the thesis were: 1) to examine the associations of total and type-specific PA with all-cause, CVD and respiratory mortality risk in people with COPD; 2) to quantify total SB, patterns of SB accumulation and PA in people with COPD; and the correlations of SB with clinically relevant outcomes; and 3) to determine, in people with stable COPD, whether a six-week behaviour change intervention was more effective than a sham intervention in reducing total SB and the accumulation of SB in prolonged bouts, and the feasibility of such an intervention with respect to uptake, retention, and compliance. To achieve these aims, this thesis contains a literature review (Chapter 1), three published research studies and one submitted manuscript (Chapters 2-5), and a discussion and clinical implications chapter (Chapter 6). The literature review provides an overview of COPD and discusses the literature on the characteristics, determinants and measurement of PA and SB, associations of PA and SB with health outcomes, and interventions to modify PA and SB in people with COPD. Chapter 2 contains a population-based cohort study that examined the dose-response associations between total PA and the risk of all-cause, CVD, and respiratory mortality within the context of current public health recommendations; and the dose-response associations between specific types of PA and the risk of all-cause, CVD (CVD), and respiratory mortality. Established thresholds were used to examine PA in MET-hours/week in order to provide clinicians with a meaningful reference standard to guide prescription of PA and enable future studies to make direct comparisons to the magnitude of mortality risk described in the sample. Two thousand three hundred ninety-eight participants with COPD were identified from the 1997 Health Survey for England and the 1998 and 2003 Scottish Health Survey cohorts. For both total physical activity and MVPA, dose-response associations were observed with all-cause and CVD mortality risk, and with respiratory mortality risk to a lesser extent. Compared to those who reported no PA, participants who met current PA recommendations demonstrated the greatest reductions in all-cause (hazard ratio (HR) 0.56, 95% confidence interval (CI) 0.45–0.69) and CVD mortality risk (HR 0.48, 95% CI 0.32–0.71). Participants who reported adhering to at least half the recommended dosage of PA also had a reduced risk of all-cause (HR 0.75, 95% CI 0.56–1.00) and CVD mortality (HR 0.48, 95% CI 0.26–0.88). Dose-response associations with mortality risk were demonstrated for walking and sport/exercise, but not domestic PA. The results of this study demonstrate that people with COPD may still benefit from engagement in low levels of PA, particularly walking and structured exercise. The cross-sectional study in Chapter 3 utilised baseline data from the study in Chapter 4 to quantify total SB, patterns of SB accumulation and PA in people with COPD using thigh-worn accelerometry, and to examine the physiological and functional capacity correlates of SB. Of the 69 participants with COPD included in the study, who spent a mean (SD) 643 (105) min/day in SB and accumulated 374 (142) min/day of SB in prolonged bouts of ≥30 minutes, 39 participants (57%) spent ≥70% of their waking wear time in SB and were classified as ‘sedentary’. ‘Sedentary’ participants had a more unfavourable pattern of SB accumulation and spent less time in PA of any intensity. Time in SB expressed as a proportion of waking wear time was inversely correlated with light-intensity PA (r=-0.97, p<0.01), MVPA (r=-0.55, p<0.01) and exercise capacity (r=-0.33, p<0.01), but not with age, body mass index (BMI) or lung function. The results of this study indicated that people with COPD not only have high total SB but accumulate the majority of SB in prolonged bouts, and that any increase in light-intensity PA is likely to reduce SB in this population. Chapters 4 and 5 of this thesis present the methodology and findings, respectively, of a prospective, multi-centre randomised controlled trial that evaluated the effectiveness of a six-week behaviour intervention compared to a sham intervention in reducing total SB and the accumulation of SB in prolonged bouts in people with COPD, and the feasibility of such an intervention. Seventy people with stable COPD on the waitlist for pulmonary rehabilitation were randomised to either an Intervention Group that consisted of six once weekly sessions with a physiotherapist to reduce SB, or to a Sham Group that received six once weekly phone calls to m
Author: Sonia Cheng
Language: English
Subfield: Pulmonary and Respiratory Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3119265838