Johnson-Warrington, Vicki BSc; Harrison, Samantha MSc; Mitchell, Katy PhD; Steiner, Mick MD; Morgan, Mike MD; Singh, Sally PhD
Individuals with chronic obstructive pulmonary disease (COPD) often experience dyspnea and fatigue.1 Reduced physical activity and exercise tolerance due to deconditioning is also common, which can impact upon patient function and contribute to increasing disability. To quantify disability caused by breathlessness, patients with COPD are often assessed using the Medical Research Council (MRC) dyspnea grades.1,2 To further understand the degree of disability for patients with COPD, comparisons are often made to the healthy population.3–5 It is assumed that the level of disability described by the MRC grade statements is perceived in the same way by healthy subjects as patients with COPD.
Although patients with COPD are often assessed by MRC grade, the MRC grade of a healthy population has not been reported and is assumed to be 1 (“I only get breathless with strenuous exercise”).2 However, this may not be accurate; it may not be unreasonable for a healthy person to describe themselves as becoming breathless when hurrying on the level or walking up a slight hill (as per MRC grade 2). For patients with COPD who report an MRC grade of 2, this may simply be due to normal variation if healthy subjects also categorize themselves as MRC grade 2. This may be particularly important where comparisons are made between those with COPD and the healthy population in research and clinical practice.
Regular physical activity and exercise are important and there are many national guidelines and schemes to promote this within the general population.6,7 Within COPD, physical activity has become an important area to investigate as it has recently been shown that a higher level of activity is associated with a lower risk of death.8 Consequently, there has been an increase in objective physical activity monitoring (by pedometers or accelerometers) for clinical9 and research purposes10 with the aim of developing interventions to increase physical activity.
Few therapeutic interventions are available for those with mild COPD, such as those with MRC grade 2. Furthermore, there is a lack of focus for this group of patients, so characteristics of individuals with COPD with an MRC grade 2 are not as well defined. Although daily physical activity has been found to be reduced for those with COPD compared to an age-matched healthy population,3,4 details of healthy participant function, for example, MRC grade, were not reported in these studies and assumed to be unaffected; however, this may not be true. It is important to match participants for appropriate variables so as not to overestimate any differences found when making comparisons.
This study, therefore, examined individuals with COPD and healthy controls, all who assessed themselves to be MRC grade 2, in terms of physical activity and exercise capacity.
Patients with COPD were recruited from a randomized, controlled trial investigating self-management, prior to the intervention. Patients were included in the study if forced expiratory volume in 1 second/forced vital capacity ratio was < 70%, were on the Primary Care COPD register, had not attended pulmonary rehabilitation (PR) in the previous 12 months, and had no physical, neurological, or psychiatric conditions that would prevent exercise.
Healthy subjects were recruited from a study investigating normal values of the Incremental Shuttle Walk Test (ISWT). Participants were invited to take part via poster advertisements, word of mouth, a promotional stand held in the community, and intranet correspondence for staff at the recruitment site. Healthy controls were included if they had no known respiratory, cardiac, neurological, psychological, or locomotive conditions, performed normal spirometry, and were aged between 40 and 90 years, to reflect a similar age group to those with COPD.
For this study we selected all participants, in either group, with a self-reported MRC grade of 2 from the above populations, so they were matched. All participants gave written informed consent and ethical approval was obtained from the local research ethics committees. Trial registration numbers are ISRCTN35501175 and ISRCTN70138213.
All participants attended an assessment at University Hospitals of Leicester NHS Trust. Demographic data were obtained, spirometry was completed, and MRC grade was recorded by participants self-selecting the most appropriate MRC grade for them. Two ISWTs were performed as per recommendations11 and the furthest distance achieved was recorded.
All participants wore the SenseWear activity monitor (AM), and data were recorded for 12 waking hours per day, on 2 weekdays, using a methodology similar to that of Pitta et al.12,13 Participants were instructed to continue their normal daily activities while wearing the AM. The AM records total energy expenditure, step count, and time spent above different MET levels.10
For the physical activity data, the average of each variable over the 2 days was calculated. Independent t tests were used to evaluate any differences in baseline characteristics between the 2 groups. Analysis of covariance was used to evaluate exercise capacity and physical activity data, where there were significant differences in baseline characteristics between the 2 groups, with this relevant significant difference as the covariate. A χ2 test was used for nominal data. Statistics were performed using SPSS version 17.0 (SPSS, Inc, Chicago, IL). Significance was accepted at P < .05.
Table 1 shows baseline characteristics of the 83 patients with COPD and 19 healthy controls. Despite aiming to recruit healthy subjects of a similar age to patients with COPD, there was a significant difference in age between groups (P = .007). As expected, smoking pack-years was significantly higher and lung function was significantly reduced for those with COPD (P < .01). There were no significant differences (P> .05) within the healthy population in terms of exercise capacity and physical activity between ex-smokers and nonsmokers.
Table 2 shows exercise capacity in terms of the ISWT and average daily physical activity over the 2 days for healthy controls and individuals with COPD. Adjusting for baseline age, step count (F1,99= 10.52) and ISWT (F1,98= 30.78) were significantly reduced for those with COPD compared with their healthy counterparts (P < .01). There were no significant differences between groups for duration of sedentary, moderate, or vigorous physical activity; however, duration of moderate physical activity between the 2 groups approached significance when adjusted for age (F1,98= 3.27, P = .074), in favor of healthy participants. Eight of 19 healthy controls (42.11%) achieved the recommended 10 000 steps per day6 compared with only 7 of 83 COPD participants (8.43%) (P = .001).
This study has shown that exercise capacity and physical activity were significantly reduced in individuals with COPD compared with healthy participants, despite both groups categorizing themselves as equally functionally limited by MRC grade. We have also shown that healthy subjects may categorize themselves as MRC grade 2 where it would normally be assumed they would be grade 1.
The fact that healthy participants self-selected a statement that reflects a level of reduced function is interesting. These healthy participants perceive themselves to be healthy, but also, to have a level of disability that they regard as normal. Healthy individuals may accept some limitations as they become older. Assessment of an individual's own capacity may also be influenced by personal activity, confidence, and exercise history; healthy participants may automatically choose MRC grade 2 if they do not exercise. Conversely, hurrying or walking uphill may be seen as “strenuous exercise” for some.
However, despite comparing participants with the same functional disability according to the MRC grade 2 statement, those with COPD were objectively different; exercise capacity and physical activity were significantly reduced in individuals with COPD compared with their healthy counterparts. There may be several reasons for this. There may be a large spectrum of disability covered by the MRC grade 2 statement, or individuals may interpret the MRC statements differently. One assumes that the MRC grades would be perceived the same by healthy subjects and those with COPD. However, once diagnosed with a chronic, progressive condition, individuals with COPD may alter their perceptions of their abilities and function. What they considered to be hurrying when they were healthy and what they consider it to be now they are diagnosed with COPD may be different.
Many individuals with COPD may potentially reason that their reduction in activity and exercise tolerance is due to increasing age, rather than disease progression. Conversely, because of those with COPD classifying themselves as equally limited by MRC grade as some healthy adults, patients may not, therefore, consider themselves functionally limited. This may consequently have an effect on patient motivation and perceived aims of interventions as patients may be more motivated to maintain their activity to avoid decline, rather than trying to increase it when they do not perceive their function to be significantly impaired. As physical performance was significantly reduced compared to an age- and MRC-matched healthy population, this information may encourage patients with COPD to engage with interventions and change behavior, to remain active and optimize their health and function.
Even though these patients with COPD did not report a dramatic reduction in function according to MRC grade, we have objectively demonstrated that function was reduced, as individuals with COPD were not as active or fit as their healthy counterparts. Furthermore, in addition to the benefits of regular exercise and physical activity,7,8 it is therefore important to provide an intervention that increases physical performance in this group of patients with COPD. Pulmonary rehabilitation has been shown to significantly improve exercise capacity for patients with MRC grade 2,14 confirming that this group of patients does benefit from exercise training. As guidelines suggest that PR should be made available to those whose function is decreased,1 patients should not be included or excluded from PR based on MRC grade alone, but other functional measures should also be considered. Early interventions, when patients are not yet significantly limited by their disease, may help delay the downward disability spiral commonly seen within respiratory disease and reduce functional decline.15 Although these data do not confirm this, providing appropriate information and intervention to increase, or at least maintain, activity and exercise capacity when patients are still moderately active (such as those with an MRC grade of 2), would intuitively be more sensible than trying to increase activity and function when patients are already severely disabled by their disease.
Despite aiming to recruit participants of a similar age group, participants with COPD in this study were significantly older than our healthy controls. However, this difference was adjusted for by performing analyses of covariances, with age as the covariate, when comparing physical activity and exercise capacity between the 2 groups. A limitation of this study is that there was a small sample of healthy participants to compare to the COPD population, which limits the definitive conclusions that can be drawn. The small number of healthy participants who were recruited may reflect the proportion of the general healthy population with an MRC grade of 2. Replication of this study with a larger sample size of healthy participants is warranted, which would also provide the opportunity to investigate the properties of the MRC grades in this population. As all subjects were volunteers, participants may have been more active and therefore we may have overestimated activity levels of the general population. However, this was true for both groups, so the differences found should be representative when making comparisons. Our data do not show how subjects accumulated their moderate physical activity. Physical activity guidelines suggest that 30 minutes of exercising should be accrued in at least 10-minute bouts7; however, it has previously been reported that patients usually accrue this in 1-minute blocks13 instead, which may not be adequate.
Interestingly, although step count was significantly higher in the control group than in individuals with COPD, total energy expenditure was not. This may be explained by patients with COPD having an increased basal metabolic rate compared with healthy subjects.16
In conclusion, we have shown that healthy subjects may report a level of disability as demonstrated by classifying themselves as MRC grade 2. We have also shown that despite a similar level of self-reported function, physical activity and exercise capacity were significantly reduced for patients with COPD compared with their healthy counterparts. This study highlights the importance of supporting the provision of interventions to promote physical activity and exercise for those with COPD with an MRC grade of 2.
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COPD; dyspnea; exercise; physical activity