Abstract
Patients with chronic obstructive pulmonary disease (COPD) are often limited in their daily physical activity. However, the level, type and intensity of daily physical activity are not known, nor there is a clear insight in the contributing factors. The aim of this review is to describe daily physical activity of COPD patients, and to examine its relationship with demographic factors, pulmonary function, physical fitness, systemic inflammation and quality of life. A systematic literature search was conducted, including studies assessing daily physical activity in all stages of COPD by various different types of measurement techniques. In total, 47 studies were selected; 17 performance-, 20 questionnaire-, and 12 interview-based. Two studies used both a performance- and questionnaire-based method. Overall, COPD patients have a lower level and intensity of daily physical activity compared to healthy controls. This was reported by performance- as well as questionnaire-based studies, yet with a large variation (42–86% and 28–97%, respectively). Reduced daily physical activity is associated with higher levels of airway obstruction, higher levels of systemic inflammation, and lower levels of physical fitness. The association between daily physical activity and quality of life is less clear. In conclusion, this is the first review that examined the level, type and determinants of daily physical activity in COPD. It demonstrates that reduced daily physical activity frequently occurs in COPD patients, yet with a large variation. Methods of measuring and reporting daily physical activity should be more standardized.
INTRODUCTION
Daily physical activity can be defined as the actual level of physical performance one adopts in daily living (Citation1). For healthy subjects a lower level of daily physical activity is associated with higher age, being female, lower socio-economic status, and higher body-mass index (Citation2). Daily physical activity is related to, but not synonymous with functional capacity status. Functional capacity is defined as the maximal performance potential of an individual, usually determined by physical fitness and limited by disease-related impairments such as dyspnoea (Citation1). COPD patients frequently report dyspnoea induced by daily physical activity. Consequently, patients with COPD may avoid daily physical activity and end up in a downward spiral of symptom-induced immobility leading to a decrease of muscle strength and endurance, social isolation and depression (Citation3). Accurate measurement, monitoring, as well as treatment of the daily physical activities of patients with COPD may be relevant for the prevention of this downward spiral of symptom-induced immobility.
A method to assess daily physical activity level in COPD patients is by questionnaires, which enquires patients to quantify their daily physical activities during a fixed recall period. Possible disadvantages of this method are the attendance for wishful answers or presence of a recall bias (Citation4). Another method to assess daily physical activity is by interviews. The advantage of this method is that everything concerning the main subject can be discussed because the participants are encouraged to talk freely. Possible disadvantages are that this method is time consuming and retrieved data is difficult to compare with each other. Nowadays, daily physical activity in COPD patients is increasingly measured by accelerometers or pedometers. These devices assess daily physical activity in a performance-based way. Uni-axial pedometers are able to record the total number of steps per day, while multi-axial accelerometers also record intensity of physical activity and energy expenditure. Possible disadvantages of performance-based methods are that upper-extremity activities are not measured, and no specific information is recorded about the type of activity (Citation5), while this might be especially important from the patients perspective. In contrast, this specific information could be assessed with questionnaires or interviews. Performance-based instruments, questionnaires and interviews provide different, yet complementary information.
There are strong indications that daily physical activity has significant implications for disease progression, systemic inflammation, and quality of life in COPD (Citation6–8). For example, COPD patients who are regularly physically active have a lower risk of both COPD-related hospital admissions and mortality (Citation9). Further insight in the amount and determinants of daily physical activity of COPD patients could provide important clues to promote daily physical activity. The aim of this review is to examine the level, intensity and type of physical activity in patients with COPD as compared to controls, taking into account the whole range of physical activities (household-, sports-, leisure time- and work-related physical activity), assessed with performance-based as well as self-reported instruments. Furthermore, this study focuses on the relationship of daily physical activity with pulmonary function, physical fitness, systemic inflammation and quality of life.
METHODS
Data sources and search strategy
Studies were included in which movement detection devices, questionnaires and structured, semi-structured or unstructured interviews were used to assess daily physical activity. To detect these studies, a literature search was carried out using Pubmed (MEDLINE), CINAHL and Cochrane, and relevant references were checked in the selected articles. Studies between 1995 and 2009 were selected. Main inclusion criteria were chronic obstructive pulmonary disease (GOLD stage I to IV) and assessment of daily physical activity.
We excluded intervention studies without information about baseline daily physical activity, studies without a clear description of the daily physical activity measurement, studies without a measure of lung function (except for interview-based studies), and studies with healthy controls matched on daily physical activity level. Moreover, we did not include studies which used quality of life instruments to assess daily physical activity. There were no restrictions concerning sample size or study design. Language was limited to English. To select relevant literature about the level, type, and intensity of physical activities, we used the following keywords in combination with ‘COPD’: ‘physical activity’, ‘daily physical activity’, ‘activities of daily living’, ‘pedometer’, ‘accelerometer’, ‘physical activity questionnaire’ and ‘interview’.
Selection of studies
All articles were independently selected for inclusion by two reviewers. If no consensus could be achieved between the two reviewers, a third reviewer was consulted. Studies were selected when 1) there was a description of the daily physical activity level of COPD compared to healthy, and/or 2) there was a description of daily physical activity type of COPD patients, and/or 3) there was an analysis of the determinants of daily physical activity.
Unlike randomized controlled trials, there are no lists of appropriate quality assessment for observational studies. In this review, the quality assessment of the studies was performed at the inclusion: Articles had to contain a measure of pulmonary function and a diagnosis of COPD, with exception of the interview-based. In all, the instrument used to measure daily physical activity had to be described. In the selected articles including determinants of daily physical activity, the statistical analysis had to be described.
Data extraction
Information was extracted from the included studies and tabulated. The characteristics considered in each study were: patient characteristics (sample size, percentage of males, age and FEV1), daily physical activity method and outcomes, secondary outcome measures (FEV1, physical fitness, systemic inflammation and quality of life) and daily physical activity in relation to the secondary outcome measures.
Examination of data
Daily physical activity was divided into the categories performance-, questionnaire-, and interview-based. Per category, we examined the daily physical activity level of COPD patients compared to healthy controls. We examined the daily physical activity type, divided in two groups; activities that could or could not be performed anymore and activities that were difficult to perform. Next, we examined whether daily physical activity was related to measures of airflow obstruction, physical fitness, systemic inflammation and quality of life.
RESULTS
In total, 47 studies were included (). There were 752 studies found after database searching and other search strategies. Of these, 695 did not meet the inclusion criteria. Main exclusion criteria were the absence of a lung function measurement and the absence of a daily physical activity measure. After excluding articles, 47 studies remained for analysis. Daily physical activity was assessed in a performance-based way in 17 studies (Tables –); in a questionnaire-based way in 20 studies (Tables –) and in an interview-based way in 12 studies (). Two studies used both a performance- and questionnaire-based method.
FIGURE 1 Flow chart of the inclusion process.
Table 1 Daily physical activity level; Performance-based
Table 2 Daily physical activity type; Performance-based
Table 3 Daily physical Activity Determinants; Performance-based
Table 4 Daily physical activity level; Questionnaire-based
Table 5 Daily physical activity type; Questionnaire-based
Table 6 Daily physical activity Determinants; Questionnaire-based
Table 7 Daily physical activity type; Interview-based
Performance-based daily physical activity
Daily physical activity was assessed in a performance-based way in seventeen studies (Tables –). Different devices were used to assess the daily physical activity level. The most frequent used device was the DynaPort accelerometer (Citation8 studies). The number of patients per study ranged between 10 and 170. When mentioned, the majority of patients were male. The mean age of the COPD patients was above 60 years, except for 2 studies.
Daily physical activity level
Daily physical activity in COPD patients was compared with healthy controls in a performance-based way in 5 studies (). Of these, 4 determined daily physical activity with an accelerometer and one study with a pedometer. The number of included patients ranged between 11 and 50, and was low overall. The mean age was above 55 years (mean age range COPD patients 56–67; Controls 53–70 years). The majority of the COPD patients was male in all 5 studies (total 78 males versus 35 females), while the healthy controls were more equally divided (total 48 males versus 41 females). The daily physical activity level of COPD patients compared to the healthy controls was significantly lower in all 5 studies (t-test and Mann-Whitney U-test, all p < 0.01). The intensity of physical activity was also significantly lower in COPD patients (t-test, all p < 0.004) (Citation10–12). In total, when the daily physical activity level of healthy controls was set on 100%, the daily physical activity level of COPD patients expressed as a percentage of the daily physical activity level of healthy controls, was diminished to 57% (range studies 42–86%).
Daily physical activity type
Seven studies quantified the type of daily physical activity in a performance-based way by using a DynaPort accelerometer and reported the outcomes in minutes per day (). One study compared mild-to-severe patients with healthy controls, revealing that COPD patients spend significantly less time on walking and standing, and show a higher sitting and lying time (Citation11). In all studies, patients with COPD walk less than an hour a day. Inactive patients walked for less time and more slowly than active patients (t-test, p < 0.05) (Citation15).
Daily physical activity determinants
Pulmonary function
Airflow limitation expressed as the percentage of predicted FEV1 ranged between 32–90% (). Seven studies determined a (baseline) association between daily physical activity and FEV1 (Citation8, Citation11, Citation14, 15, Citation20–22). The correlations ranged between 0.28 and 0.62, all significant (p < 0.01). One study reported a non-significant correlation between steps per day and FEV1 (r = 0.25, p-value not mentioned) (Citation23). In one study inactive patients showed a lower mean FEV1 compared to the mean of active patients (t-test, p < 0.05) (Citation15). One study reported significant main effect on steps per day from two-way ANOVA of GOLD stages (Citation8).
Physical fitness
Physical fitness was assessed in eight performance-based studies (). As measurement tools of physical fitness, the 6-minute walk test (6MWT) (7 studies), quadriceps strength (3 studies), handgrip strength (3 studies), cycle ergometry (1 study), and steady state exercise test (one study) were used. Five out of 7 studies using the 6-minute walk test, demonstrated a moderate to strong correlation with daily physical activity (range r = 0.49–0.76, p < 0.002) (Citation11, Citation15, Citation21, 22, Citation24). Two other studies reported no such association (Citation10, Citation23). Only one study reported a significant association between daily physical activity and muscle strength (r quadriceps = 0.45, p < 0.01, r handgrip = 0.44, p < 0.01) (Citation11). Inactive patients showed a lower exercise tolerance compared to active patients (p < 0.05) (Citation15).
Systemic inflammation
There were two performance-based studies focusing on systemic inflammation (). The first study found an association between reduced daily physical activity and higher values of systemic inflammation (high-sensitivity C-reactive protein and fibrogen), independent of GOLD stage or BODE-index (Citation8). Another study demonstrated an inverse relation between daily physical activity and markers of systemic inflammation such as high-sensitivity C-reactive protein (r = −0.18, p = 0.01), interleukin-6 (r = −0.23, p < 0.001) and fibrinogen (r = −0.25, p < 0.001) (Citation25).
Quality of life
Quality of life was measured in six studies, using the Saint George Respiratory Questionnaire (Citation4 studies), the SF36 (2 studies), and the Chronic Respiratory Disease Questionnaire (2 studies) (). Two out of 4 studies using the Saint George Respiratory Questionnaire reported the results of their associations. One study reported a negative association between daily physical activity and quality of life (r = −0.28, p < 0.01) (Citation20), whereas the other study reported no association (Citation10), One out of 2 studies using the SF36 reported that the physical subscale of the health status questionnaire was significant positively correlated with daily physical activity (r = 0.40, p < 0.001) (Citation21), whereas correlation with the mental subscale was not (r = 0.15, not significant) (Citation21), One study using the Chronic Respiratory Disease Questionnaire reported a non significant correlation with daily physical activity (r = 0.17, not significant) (Citation21). The other study that used this questionnaire did not report any difference between inactive COPD patients and active COPD patients (groups based on compliance with the guideline: minimum of 30 minutes of walking per day) (Citation15).
Questionnaire-based daily physical activity
Daily physical activity was assessed by various questionnaires in 20 studies (Tables –). The most frequent used questionnaire was the Baecke Physical Questionnaire for the elderly (7 studies). The number of patients per study ranged between 9 and 3608. When mentioned, the majority of patients were male. The mean age of the COPD patients in the studies was above 60 years, except for 2 studies.
Daily physical activity level
Daily physical activity in COPD patients was compared with healthy controls in a questionnaire-based way in 7 studies () (Citation26–32). The number of included patients ranged between 9 and 68, and was low overall. The mean age was above 58 years (mean age range COPD patients 58–68; Controls 58–64 years). The male/female ratio was not mentioned in all studies, but when mentioned the majority of the COPD patients was male, except for 1 study (total 120 males versus 68 females), which also holds for healthy controls (total 115 males versus 86 females). The daily physical activity level of COPD patients compared to the healthy controls is significantly lower in 5 out of 7 studies (t-test, Fisher exact probability test, and Mann-Whitney U-test, all p < 0.05) (Citation26–29, Citation32). In total, when the activity level of healthy controls was set on 100%, the daily physical activity level of COPD patients expressed as a percentage of the daily physical activity level of healthy controls, was diminished to 70% (range 28–97%).
Daily physical activity type
Daily physical activity type was assessed in a questionnaire-based way in 4 studies (). The activities that could not be performed anymore were: sports (Citation27, Citation33), work (Citation27, Citation34), and leisure-time physical activities (Citation27). Patients with a higher level of airflow obstruction (FEV1 < 50%) reported the worst dysfunction in everyday life, defined as walking, eating, home management and recreation (Citation27). COPD patients differed from healthy controls in walking activities and mobility (Citation27).
Daily physical activity determinants
Pulmonary function
Airflow obstruction, measured by FEV1% predicted, ranged between 32% and 78% (). Eleven questionnaire-based studies reported on the relation with daily physical activity. Nine out of 11 studies reported an association between severity of disease and decrease of daily physical activity level (range r = 0.10–0.63, p < 0.05) (Citation7, Citation9, Citation21, Citation32, Citation35–39). One study used 2 daily physical activity questionnaires with a high score representing inactivity and reported a negative correlation between outcomes of the daily physical activity questionnaires and FEV1% predicted (r = −0.11 and r = −0.72, p = 0.001) (Citation28). Two other studies did not demonstrate a (significant) relation between daily physical activity and FEV1% predicted (Citation29;Citation40).
Physical fitness
Physical fitness was assessed in 8 studies (). Physical fitness was measured by the 6-minute walk test (three studies), cycle ergometry (3 studies,) quadriceps strength (4 studies), handgrip strength (1 studies), and arm strength (1 study). When measured with the 6MWT, one study showed that physically active patients perform better on the 6MWT test (Citation7). One study reported a positive correlation (r = 0.35, p < 0.01) (Citation21). When measured with a cycle ergometer, one study reported a positive correlation with daily physical activity (r = 0.60, p < 0.01) (Citation32), whereas 2 other studies did not report a significant association (Citation29, Citation40). There was no significant association reported between quadriceps strength and daily physical activity. One study reported a positive non-significant correlation (r = 0.04, NS) (Citation32), one a negative correlation (r = −0.32, NS) (Citation41), and 2 other reported no association (Citation26, Citation29).
Systemic inflammation
One questionnaire-based study focussed on systemic inflammation (). In this study, Garcia-Aymerich demonstrate that more physically active COPD patients have lower levels of systemic inflammation (TNF-α, interleukin-6, interleukin-8 and C-reactive protein) (Citation7). No differences were found in body-composition and weight between the physical activity groups.
Quality of life
Quality of life was measured in 5 studies using the Chronic Respiratory Disease Questionnaire (two studies), the Clinical COPD Questionnaire (1 study), the Saint George Respiratory Questionnaire (one studies), SF36/SF12 (1 study), and the Visual Analog Scale (1 study) (). Three studies demonstrated a significant positive association between daily physical activity and quality of life (total and individual domain scores) (range r = 0.17–0.48, p < 0.01). (Citation33, Citation36, Citation37), whereas 1 study using 2 different quality of life questionnaires reported a non-significant negative association with daily physical activity (CRQ r = −0.21, NS; SF36 physical and mental subdomains r = −0.01 and 0.02, NS) (Citation21).
Interview-based type of daily physical activity
The type of daily physical activity was assessed by interview in 12 studies (). Most of these studies included small numbers of patients (range 6–100), apparently because the method is time consuming. Except for 2 studies, most patients were male. The mean age was above 60 years. In all included studies the FEV1 (when mentioned) was below 50% predicted or disease state was described as ‘moderate-to-very severe’. Activities that could not be performed anymore are: everyday tasks (including self-care) (Citation44), household activities (Citation45, 46), traveling (Citation44, Citation47), social activities (Citation46–48), hobbies (Citation47), sports (Citation45), and work (Citation45, Citation48). The activities difficult to perform are: everyday tasks (including self-care) (Citation45, Citation49-52), household activities (Citation49, Citation52, Citation53), leisure time activities such as walking (Citation54), traveling (Citation52, Citation54), and sports (Citation47). In general, females report more performance difficulties in home management tasks and hobbies. They tend to hold on to household activities as long as possible and experience great difficulty dropping these.
DISCUSSION
In this study we systematically reviewed daily physical activity in COPD patients, categorized in performance-, questionnaire- and interview-based daily physical activity. The results demonstrate that daily physical activity for COPD patients is lower than in healthy controls and lower than what the international guidelines recommend to maintain or enhance physical health and fitness. This lower level of daily physical activity for COPD patients is associated with a higher level of airway obstruction, a lower level of physical fitness, and higher levels of systemic inflammation.
Daily physical activity level
The level of daily physical activity of COPD patients is about 57% (range studies Citation42–86%) of that of healthy age-matched controls in performance-based studies, and about 70% (range 28–97%) in questionnaire-based studies. These results demonstrate that there is a large range in the level of daily physical activity in COPD patients, even when measured with one and the same method. This large range could be due to different patient characteristics, different settings, and different measurement protocols. In this respect it should be noted that very few of the methods to assess daily physical activity, particularly the questionnaires, have been validated for COPD patients. From epidemiological studies, it is well known that a large range in the daily physical activity level is quite usual in healthy as well as diseased subjects, even after adjusting for age and sex (Citation2, Citation20, Citation56). An interesting observation of this review are the overall smaller differences in daily physical activity level of COPD patients compared to healthy controls, when assessed with a physical activity questionnaire than with performance-based measurement. Apparently, COPD patients are very well aware of accomplishing small routine daily activities that are not perceived by healthy controls. Another possible explanation is that COPD patients dissimulate their disease and give wishful answers.
Determinants of daily physical activity level
This review demonstrates that in a large number of studies daily physical activity correlated positively with airway obstruction (Citation7–9, Citation11, Citation14, Citation15, Citation20–22, Citation32, Citation35–39), 6-minute walk test (Citation7, Citation11, Citation15, Citation21, Citation22, Citation24), and muscle force (Citation11, Citation15). Although not all studies reported significant associations between daily physical activity and the secondary measurement, the studies that did, reported moderate to strong associations, especially those with airway obstruction and the 6-minute walk test. Regarding the association with demographic factors, it is well known that daily physical activity in healthy subjects diminishes with aging. This review confirmed this by a few studies reporting that higher age was indeed associated with lower daily physical activity level (Citation7, Citation33). A large questionnaire-based study on characteristics of COPD patients revealed that a lower level of daily physical activity is significantly associated with female sex, older age, higher socioeconomic status, and lower physical as well as mental quality of life (Citation33).
Daily physical activity and systemic inflammation
There are three studies focusing on daily physical activity in relation to systemic inflammation. All 3 studies demonstrate that lower daily physical activity level is related to higher levels of systemic inflammation. Such relationships have also been demonstrated in healthy subjects and other chronic diseases (Citation57–60). Whether reduced daily physical activity in COPD is cause rather than consequence of increased systemic inflammation remains unclear.
Daily physical activity level and quality of life
This review reveals that for COPD patients daily physical activity in a number of studies is significantly possitively correlated with health related quality of life (Citation21, Citation33, Citation36, 37). On the other hand, there were a few studies that reported a significantly negative association (Citation20,21). An explanation for this discrepancy may be the use of different methods to assess daily physical activity and quality of life, difference between COPD populations, and low sample size. It is worthwhile to note that studies demonstrating a significant correlation frequently used questionnaire-based daily physical activity scores, whereas some of them also used a quality of life score that included questions directly related to daily physical activity. There were no positive correlations demonstrated in performance based studies. The absence of a clear relationship is in line with a previous systematic review on the effects of daily physical activity (Citation61). An explanation for this maybe that many COPD patients during their slowly progressing disease gradually accept their sedentary life style. This finding is in line with large cross-sectional studies that demonstrate that perceived quality of life remains quite high in many COPD patients, even in the more severe disease stages (Citation62,63). The same cross-sectional studies also demonstrate an enormous range of quality of life scores within different disease stages of COPD; so it might be that a proportion of COPD patients actually do not psychologically accept their disease state at all. This may, at least partly, explain the inconsistency of findings of the cross-sectional studies with respect to the positive correlation between daily physical activity and quality of life. Studies including this aspect of psychological adaptation are clearly needed to further support this.
Daily physical activity type
Not performed activities were mostly recreational and hobbies (walking and holidays), work, household, social, and everyday tasks (including self-care). Mostly reported difficulties to perform activities were: everyday tasks (including self-care), recreational and hobbies, household, and social. Interestingly, males and females withdraw their activities in a different order. Females tend to hold on to household activities as long as possible, and experience more difficulty in performing home management tasks and hobbies. This could mean that males and females should be treated in a different way when they participate in a physical enhancement or pulmonary rehabilitation program. The specific information about the types of daily physical activity that are being avoided and the order of withdrawal could have important implications for patient as well as physician. Not being able to perform certain types of physical activity, especially the types that reduce autonomy, may affect a patient's quality of life.
Intervention studies targeting at daily physical activity
Interventions can be primarily targeted at increasing physical activities, theoretically followed by improvements of physical fitness. The usefulness of such a strategy is suggested by a meta-analysis of Chavannes, which included 5 studies that targeted physical activities like walking, cycling, swimming and/or training of large muscle groups (Citation61). One research group performed two studies that used performance-based instruments in order to motivate COPD patients to increase their number of steps and other daily activities (Citation64, 65). Such a strategy is in line with a recent review on stimulation of daily physical activity in healthy and diseased subjects showing that pedometers can be very useful in the enhancement of daily physical activity. The effects of this enhancement are even larger when an individually based target was formulated using the goal setting technique (Citation66). From these studies, it may be concluded that at least a subgroup of COPD patients may benefit from interventions that primarily target daily physical activity, yet such programs have to be tailored and further optimized.
CONCLUDING REMARKS
The results of this review clearly demonstrate that the daily physical activity level in COPD patients is lower compared to healthy controls. This lower level of daily physical activity is associated with a higher level of airway obstruction, a lower level of physical fitness, and higher levels of systemic inflammation. There is no consensus on the association between a lower level of daily physical activity and quality of life.
Two important unmet needs have to be defined for future management and research:
Daily physical activity is an underestimated yet important outcome measure that should be measured routinely in the general management of COPD, and in observational and intervention studies.
The methods of measuring and reporting daily physical activity in COPD should be standardized.
| ABBREVIATIONS | ||
| COPD | = | Chronic Obstructive Pulmonary Disease |
| FEV1 | = | Forced Expiratory Volume in 1 Second |
| SGRQ | = | Saint George Respiratory Questionnaire |
| 6MWT | = | Six-Minute Walk Test |
| BMI | = | Body Mass Index |
| BMR | = | Basal Metabolic Rate |
| CCQ | = | Clinical COPD Questionnaire |
| CRP | = | C-reactive protein |
| CRQ | = | Chronic Respiratory Disease Questionnaire |
| EE | = | Energy Expenditure |
| FFMi | = | Fat-Free Mass index |
| Kcal | = | Kilo-calories |
| MET | = | Metabolic Equivalents |
| MRC | = | Medical Research Council |
| MVC | = | Maximal Voluntary Contraction |
| REE | = | Resting Energy Expenditure |
| TEE | = | Total Energy Expenditure |
| TNF | = | Tumor Necrosis Factor |
| VAS | = | Visual Analog Scale |
| VMU | = | Vector Magnitude Units |
DECLARATION OF INTEREST
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
ACKNOWLEDGMENTS
This study was supported by a non-restricted grant of Boehringer Ingelheim.
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