Background
Description of the condition
Chronic obstructive pulmonary disease (COPD) is a common, treatable but incurable obstructive lung disease defined by persistent airflow limitation. Diagnosis is determined by spirometry in the clinical context of a person presenting with dyspnoea, chronic cough or sputum production, and a history of risk factor exposure (GOLD 2017). Development of COPD is primarily attributable to an enhanced chronic inflammatory airway response to noxious particles or gases and is strongly linked to a history of smoking. However, there are a number of other risk factors including exposure to air pollution, occupational exposures, genetics, asthma, history of severe childhood respiratory infection and low socioeconomic status (GOLD 2017). Systemic effects, including systemic inflammation and muscle dysfunction, and comorbid conditions, including cardiovascular disease, anxiety and depression, are associated with COPD (Choudhury 2014). Prevalence estimates suggest that COPD affects upwards of 384 million people (Adeloye 2015), and is the third leading cause of death worldwide (WHO 2017). Associated with advancing age (Anton 2016), and in the context of the fastest rate of population growth occurring in people over 65 years of age (UN 2015), COPD poses a substantial and growing economic and social burden (GOLD 2017).
Description of the intervention
The term ‘physical activity’ is defined as any bodily movement produced by skeletal muscles that results in energy expenditure (Casperson 1985). It is a complex behaviour traditionally described according to type, intensity and duration, and incorporates a subset of undertakings including exercise, occupational and household activities. Public health promotion for regular participation in physical activity typically references a minimum 150 minutes per week of at least moderate intensity activity in bouts of greater than 10-minutes duration as ‘sufficient’ for health benefits across the adult population (WHO 2010). These benefits include reduced risk of all-cause mortality, coronary heart disease, hypertension, stroke, metabolic syndrome, type 2 diabetes and depression (Lee 2012).
Participation in regular physical activity is also endorsed for people with COPD (GOLD 2017). Inactivity is one of the main risk factors for development of cardiovascular, metabolic and musculoskeletal comorbid conditions in people with COPD, and is observed across the disease spectrum (Van Remoortel 2014). Recent studies show that physical activity is reduced in smokers prior to diagnosis (Furlanetto 2014), in people with a recent diagnosis and mild COPD before symptom onset (Johnson-Warrington 2014), and is independent of other clinical characteristics including impaired exercise capacity (Fastenau 2013; Gagnon 2015; Van Remoortel 2013; Watz 2009). Physical activity participation is reduced compared to healthy peers (Pitta 2005; Vorrink 2011), and to people with other chronic conditions (Arne 2009). It is further compromised during and after hospitalisation for an acute exacerbation (Pitta 2006a), and with increasing disease severity (Shrikrishna 2012; Troosters 2010; Waschki 2015). In people with COPD, low levels of participation in physical activity have been independently associated with poor outcomes, including increased risk for hospitalisation and mortality (Garcia-Aymerich 2006; Garcia-Rio 2012; Vaes 2014; Waschki 2011).
Much attention has been given to the development of physical activity interventions that incorporate strategies specifically designed to promote the adoption and maintenance of active lifestyles in the general population (Marcus 2006). For the purposes of this Cochrane Review, an intervention is any approach used with the specific purpose of increasing objectively measured physical activity in people with COPD. Such interventions may be provided by a broad range of healthcare professionals and be delivered in a variety of ways (for example, face to face, via internet or telephone).
How the intervention might work
Evidence suggests that people with COPD avoid participation in physical activity due to the perception of breathlessness, resulting from inefficiencies related to gas trapping and lung hyperinflation. A vicious circle is perpetuated, where muscle deconditioning results from avoiding activities that involve physical exertion and exacerbate symptoms, further compromising physical capacity to engage in activity (O’Donnell 2014). It is theorised that targeted interventions may be able to interrupt this cycle and increase participation in physical activity at a range of intensities that are associated with health benefits. The dual role of physical inactivity as both a cause and consequence in chronic disease identifies physical activity as a potentially modifiable target that could affect health-related quality of life and disease trajectory (Esteban 2010; Vaes 2014; Watz 2014). Whether improvements in physical activity can ameliorate these effects in COPD is unknown.
Many physical and physiological disease features also appear to influence participation in physical activity by people with COPD. However, the quality of association between such features, including lung function, systemic inflammation, body composition, co-morbidities and psychosocial factors, and physical activity participation is variable (Gimeno-Santos 2011). Additional considerations, including fatigue (Andersson 2015), balance (Iwakura 2016), and seasonal and environmental factors (Alahmari 2015; Sewell 2010), may also impact on physical activity participation in this group. The broad range of strategies considered to date to address physical inactivity in people with COPD (for instance, exercise training, nutritional interventions and behavioural strategies) reflects the complexity of this issue.
Increased physical activity has been associated with reduced rate of exacerbations (Esteban 2014), which highlights that targeting improvements in physical activity in people with COPD may be an important therapeutic goal (Langer 2016; Singh 2016). However, achieving consistent improvements in participation and strong evidence for the positive impact on health outcomes remain elusive.
Why it is important to do this review
Escalating awareness of the magnitude of the challenge posed by physical inactivity in COPD at all points in the disease course highlights the need for interventions to address the limited participation in physical activity by people with COPD. The widely accepted benefits of physical activity, coupled with the increasing availability of wearable monitoring devices to objectively measure participation, has led to a dramatic rise in the number and variety of studies that aim to improve physical activity levels in people with COPD. However, little is known about the relative effectiveness of interventions tested so far, partly attributable to the complexities of data analysis and challenge of rapidly evolving technology. Whether improvements in physical activity are accompanied by improved exercise capacity and health-related quality of life is unknown. This Cochrane Review aims to evaluate the efficacy of existing interventions to increase physical activity in people with COPD and signpost directions for future work.