https://orcid.org/0000-0002-4178-2905
Abstract
Depression and anxiety are related to physical activity among people with chronic obstructive pulmonary disease (COPD), although the strength and direction of the reported relationships are inconsistent. This study systematically synthesized the relationships between physical activity and i) depression and ii) anxiety in people with COPD. Physical activity measurement type (objective, self-report) was examined as a moderator of these relationships. A systematic search of physical activity and COPD was conducted from inception to February 2022 across 8 databases. Studies were included if they provided correlation coefficients for the relationship between measures of physical activity and depression or anxiety in people with COPD and were published in English. Two reviewers independently screened, reviewed and extracted data, with discrepancies resolved by a third reviewer. Across 13 studies, a small relationship was found between physical activity and depression, weighted r = −0.15, 95%CI [-0.21, −0.10], which was not moderated by physical activity measurement type. Across 8 studies, a negligible relationship was found between physical activity and anxiety, weighted r = −0.03, 95%CI [-0.11, 0.04], although this was moderated by physical activity measurement type, such that self-reported physical activity had a small negative relationship with anxiety (weighted r = −0.09, 95% CI [-0.15, −0.03]) and objectively measured physical activity had a small positive relationship (weighted r = 0.07, 95% CI [-0.13, 0.26]). In COPD, the bivariate association between physical activity and anxiety and depression are small.
Background/introduction
In people with chronic obstructive pulmonary disease (COPD), higher levels of physical activity (PA) are associated with a reduced risk of hospitalizations, acute exacerbations, and mortality [Citation1–3]. However, low levels of PA are common among people with COPD [Citation4–6] and strategies to increase PA, including exercise training, pharmacological management, and PA counseling have been found to have limited success in this population [Citation7]. Ekkekakis and Zenko [Citation8] suggest that this lack of success may reflect strategies omitting to address affective characteristics. Affect is defined as “the experience of feelings, emotion, or mood, which are known to influence behavior” [Citation9]. In COPD, anxiety and depression are the most prevalent affective characteristics studied [Citation10] and negatively impact prognosis [Citation11]. Anxiety has been found in up to 40% and depression in up to 25% of people with COPD [Citation12], both having been linked to worsened health status, increased exertional dyspnea and poor quality of life [Citation13].
Investigating whether a relationship is present between anxiety and depression and physical activity is the first step toward determining whether these affective characteristics might be fruitful targets of interventions designed to increase physical activity. In COPD, the relationship between symptoms of anxiety and depression and PA has been investigated, although there is variability in both the size and direction of the relationships reported. For depression and PA, no association [Citation14], a positive association [Citation15] and a negative association [Citation16] have been reported. For anxiety and PA, both positive [Citation17] and negative relationships [Citation18] have been reported. A systematic synthesis of the relationship between anxiety, depression, and PA will provide a more robust estimate of the true effect of these relationships to help identify treatment targets.
Our primary objective was to systematically synthesize the literature on and estimate the relationships between PA and i) depression and ii) anxiety in adults with COPD. Given the impact of measurement on associations between constructs [Citation19], our secondary objective was to determine the moderating role of PA measurement type (i.e. self-report versus objective) in the depression and anxiety meta-analyses.
Methods
We registered the meta-analysis protocols with PROSPERO (CRD42020200254) and used the PRISMA framework to guide this research.
Search details
We searched Ovid MEDLINE: Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE Daily and Ovid MEDLINE, OVID Embase, Ovid PsycINFO, EBSCO CINAHL Plus, EBSCO SportDiscus, and Cochrane CENTRAL from inception to present to identify research articles examining exercise interventions in people with COPD. Search strategies were developed by an academic health science librarian (EN) in collaboration with the project leads. The search strategies were translated using each database platform’s command language, controlled vocabulary, and appropriate search fields. MeSH terms, EMTREE terms, APA thesauri terms, CINAHL headings, SIRC terms, and text words were used for the search concepts of COPD and exercise. Filters to remove animal studies were applied to the Medline and Embase search strategies. No date or language limits were imposed. Our initial search was completed on June 4, 2020 and then was re-executed on February 1, 2022.
Inclusion and exclusion criteria
We included studies if: (a) they were conducted among adults diagnosed with COPD, (b) they measured PA and anxiety or depression, (c) they reported correlation coefficients (Pearson’s r) of the association between PA and anxiety or depression or statistics that could be converted to Pearson’s r (e.g. odds ratios), and (d) they were published in English-language journals. Eligible study settings included community programs, pulmonary rehabilitation (home-based, outpatient, inpatient), and acute care. Studies were excluded if: (a) they were not published in a peer-reviewed journal, (b) they were qualitative studies, reviews, editorials, opinion pieces, letters to the editor, case reports, or lessons learned, (c) they contained a mixed sample that combined patients with a diagnosis of COPD with other respiratory or health diagnoses, (d) they did not use an instrument (e.g. accelerometer, pedometer, questionnaire) to measure PA and (e) they did not report a distinct measure of anxiety or depression .
Study selection and data extraction
We imported the results of the database search into EndNote and then into Covidence, which we used to track and manage the review process. At least two researchers (RH, LE, AS, CE) were involved at every stage of data screening and reviewing, extraction, and evaluation. We resolved disagreements by a consensus method (discussion followed by third researcher resolution).
Two reviewers independently screened titles and abstracts to identify articles of potential relevance. Subsequently, we reviewed full-text articles were for inclusion or exclusion. We retained articles that met the inclusion criteria in the full-text screening phase for data extraction. We further searched the reference lists of retained articles to identify additional potentially relevant studies.
Two authors extracted all data. We extracted descriptive data from each study, including country where the study was conducted, main purpose of the study, study setting, study design, main inclusion criteria for COPD diagnosis, sample size, proportion of female participants, participants mean age, smoking history, education, spirometry, measures of PA and anxiety or depression, proportion of self-report PA measures, and indicators of the association between PA and anxiety or depression.
Quality assessment
We used the Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a Variety of Fields [Citation20] to assess potential bias. Two reviewers independently scored the studies according to the criteria of this scale, and a mean quality score was calculated for each article (see and ). As recommended by Kmet et al. [Citation20] we only included studies that met the minimum threshold of 65% for analysis.
Table 1. Summary of Studies Included in the Depression Meta-Analysis.
Table 2. Summary of Studies Included in the Anxiety Meta-Analysis.
Definitions of variables and coding
We coded PA measures as either self-report or objective to examine the moderating effects of the physical activity measurement type. Self-reported physical activity was defined as measurements where the individual personally provided information on their physical activity amount, intensity and/or duration. Objective physical activity was defined as measurements where the physical activity amount, intensity, and/or duration was externally quantified.
Analysis
We used MetaXL software for our analysis to calculate the average effect estimates, heterogeneity statistics, and to produce forest and funnel plots. A random effects model of correlation coefficients was used to estimate the population effect size. If necessary, correlation coefficients were recoded to represent the same direction of association. For example, the studies that provided odds ratios were converted to correlation coefficients [Citation21] and their signs were changed as necessary to reflect the direction of the association found in the original study. When multiple correlation coefficients were provided for PA and one of the outcomes (anxiety or depression), we combined the correlation coefficients for that outcome using the procedure outlined by Schmidt and Hunter [Citation19]. We computed funnel plots to determine the presence of bias, with asymmetrical plots indicating the presence of bias [Citation22]. Forest plots displaying effect estimates and confidence intervals for the individual studies and meta-analysis were used to illustrate the results [Citation22]. We assessed heterogeneity using the Q and I2 statistic [Citation22] and sub-group analyses were conducted for physical activity measurement type (i.e. self-report, objective).
Results
Description of studies and content analyzed
Depression
A total of 13 studies met the inclusion criteria () and contributed 13 correlation coefficients, totaling 10,072 participants, to the meta-analysis. The sample sizes of the studies were between 29 and 6,293. The studies were conducted in the United States of America [Citation17, Citation23], the Netherlands [Citation18], Canada [Citation24], Portugal [Citation25], Spain [Citation16, Citation26–28], Japan [Citation29, Citation30], South Korea [Citation15], and China [Citation31] between 2003 and 2021. The most common study design was cross-sectional (k = 11), followed by longitudinal (k = 1), and quasi-experimental (k = 1). Across studies the mean age was 66.5 (SD = 5.2), comprised of 23% female participants. The mean FEV1% predicted was 51.7 (SD = 6.2, range = 41 – 63%). The most common measure of depression was the Hospital and Anxiety and Depression Scale [Citation32] (HADS) (n = 9), followed by the Center for Epidemiological Studies Depression Scale [Citation33] (CES-D) (n = 2), the Beck Depression Inventory [Citation34] (BDI) (n = 1) and self-report of previous diagnosis of depression (n = 1). Physical activity was measured by self-report in eight studies [Citation15, Citation16, Citation23, Citation24, Citation26–28, Citation31] and objectively in 5 studies [Citation17, Citation18, Citation25, Citation29, Citation30]. The characteristics of each study are outlined in .
Figure 1. Study flow-diagram.
Anxiety
A total of eight studies met the inclusion criteria () and contributed eight correlation coefficients, totaling 8,337 participants, to the meta-analysis. The sample sizes of the studies were between 29 and 6,293. The studies were conducted in the United States of America [Citation17], the Netherlands [Citation18], Canada [Citation24], Spain [Citation27, Citation28], Japan [Citation29, Citation30], and China [Citation31] between 2018 and 2021. There was one longitudinal study, and the remaining were cross-sectional (k = 7). Across studies the mean age was 65.4 (SD = 6.4), comprised of 27% female participants. The mean FEV1% predicted was 51.1 (SD = 7.6, range = 41 – 63%). The majority of studies used the HADS [Citation32] to measure anxiety (n = 7) while one used self-report of a previous diagnosis of anxiety. The characteristics of each study are outlined in .
Results of meta-analysis
Depression
The funnel plot () was approximately symmetrical, suggesting no presence of bias. There was variability in the relationship between depression and PA across the studies as evidenced by the shape of the funnel plot and a larger I2 statistic, which may indicate the presence of a moderator or bias (e.g. measurement).
Figure 2. Funnel plot for depression and physical activity meta-analysis. Approximate symmetry suggests no bias is present.
The estimate of the overall relationship between depression and PA was small (weighted r = −0.15, 95%CI [-0.21, −0.10]), with greater depression associated with less PA. In the subgroup analysis of PA measurement type, objectively measured PA (weighted r = −0.13, 95% CI [-0.26, 0.01]) had a similar association to depression as self-report measured PA (weighted r = −0.17, 95% CI [-0.23, −0.11]). The five studies measuring PA objectively [Citation17, Citation18, Citation25, Citation29, Citation30] contributed fewer participants to the analyses (n = 614) and had wider confidence intervals for the effect estimate, than the eight studies measuring PA by self-report [Citation15, Citation16, Citation23, Citation24, Citation26–28, Citation31] (n = 9,458). displays the Forest Plot, estimates of the average effect, heterogeneity statistics, and subgroup analysis.
Figure 3. Individual study and pooled results of the relationship between depression and physical activity presented by physical activity measurement type (self-report or objective).
Anxiety
The funnel plot () was approximately symmetrical, suggesting no publication bias. There was variability in the relationship between anxiety and PA across the studies as evidenced by the shape of the funnel plot and a larger I2 statistic, which may indicate the presence of a moderator or bias (e.g. measurement).
Figure 4. Funnel plot for anxiety and physical activity meta-analysis. Approximate symmetry suggests no bias is present.
The estimate of the overall relationship between anxiety and PA was negligible (weighted r = −0.03, 95%CI [-0.11, 0.04]). Physical activity measurement type (objective vs self-report) moderated this relationship. When PA was measured objectively, there was a small positive association between anxiety and PA (weighted r = 0.07, 95% CI [-0.13, 0.26]), and when PA was measured by self-report, there was a small negative association between anxiety and PA (weighted r = −0.09, 95% CI [-0.15, −0.03]). The four studies measuring PA objectively [Citation17, Citation18, Citation29, Citation30] contributed fewer participants to the analyses (n = 599) and had wider confidence intervals for the effect estimate, than the four studies measuring PA by self-report (n = 7,778) [Citation24, Citation27, Citation28, Citation31]. displays the Forest Plot, estimates of the average effect, heterogeneity statistics, and subgroup analysis.
Figure 5. Individual study and pooled results of the relationship between anxiety and physical activity presented by physical activity measurement type (self-report or objective).
Discussion
This study systematically synthesized the relationship between PA and two important affective characteristics in COPD: symptoms of depression and anxiety. The small negative relationship between PA and depression was independent of whether PA was measured by self-report or objectively. The full sample meta-analysis for PA and anxiety showed no relationship between these variables, although self-reported PA had a small negative association with anxiety and objectively measured PA had a small positive association.
The relationships between depression, anxiety and physical activity were weak. The HADS [Citation32], Beck Depression Inventory [Citation34], and other common measures of anxiety and depression symptoms are considered trait assessments (i.e. a tendency to present a state over a period of time, such as 2-weeks) [Citation35]. However, PA may be more closely related to depressive or anxious states (i.e. a transient or moment-to-moment reaction) than their respective traits [Citation35]. That is, how someone feels in the moment they intend to initiate PA may be more important than how they have generally been feeling over the last two weeks. This hypothesis is consistent with contemporary behavioral theories [Citation36] which suggest that emotional impulses are important aspects of motivation and behavior.
Another contributor to the reported relationships between physical activity and anxiety and depression relates to the validity of the Hospital Anxiety and Depression Scale (HADS) [Citation32], which was the most commonly used measure to assess both depression (9/13 studies) and anxiety (7/8 studies). The discriminant validity of this measure in COPD remains questionable [Citation37, Citation38]. Nowak et al. [Citation38] found that among people with COPD, the HADS accurately predicted the presence of depression in only 17.3% individuals with preexisting diagnoses of depression. Cheung et al. [Citation37] found moderate diagnostic value for anxiety in people with COPD. Furthermore, the approach recommended to improve the sensitivity and specificity for depression by item removal and modified cutoff values, was not used [Citation39].
The type of PA measurement had a minor impact on the relationship with anxiety and none on the relationship with depression. A stronger relationship between self-reported PA and self-reported anxiety and depression was expected, given the congruence between the measurement types. The cumulative sample size for studies using objective measures of PA was small (n = 559) and had wide confidence intervals for the effect estimate. Conceivably a larger cumulative sample size may have resulted in a more accurate effect estimate of the relationship between objectively measured PA and anxiety in COPD.
Identifying modifiable targets that increase PA remains a priority given the negative impact of low levels of PA on morbidity and mortality in COPD [Citation1–3]. Cumulatively, the studies we summarized did not appear to support the notion that improving anxiety and depression will increase PA, although meta-analyses have found the converse, such that increasing PA improves anxiety [standardised mean difference (SMD) = −0.38; 95% CI: −0.66 to −0.11] and depression [SMD = −0.50; 95% CI: −0.93 to −0.06] [Citation40]. There may be unidentified moderators or mediators, such as gender or dyspnea and functional capacity, respectively, that may impact the relationship between anxiety, depression, and physical activity in COPD. Altenburg et al. [Citation18] found that depression indirectly contributed to physical activity in COPD through functional exercise capacity, with depression having a significant negative relationship to physical activity among those walking greater than 452 meters on the 6-minute walk test and unrelated to those walking less. Additionally, Nguyen et al. [Citation17] found that depression was associated with less physical activity in people with COPD only when anxiety was adjusted for. As such, there is evidence that anxiety and depression have indirect relationships to physical activity and may require complex statistical analyses to understand the nature of these relationships in full. Future research is needed to better understand anxiety and depression as potential antecedents and outcomes of physical activity in COPD.
The meta-analyses provide a current estimate of the relationships between PA and depression and anxiety, although there are limitations of this research. Several published studies were excluded as they did not provide the appropriate statistics. Additionally, most studies were cross-sectional, limiting inferences of causality and direction of the relationships between PA and depression and anxiety. While the meta-analyses controlled for sampling error and study quality, it did not control for other artifacts, such as measurement error [Citation19], and did not include grey literature, which might have impacted the estimated correlation coefficients. As there were only a few studies included in the moderator analysis, the results of this analysis should be interpreted with caution. Further, the meta-analysis included multiple instruments assessing anxiety and depression, which impacts the comparisons across studies.
Conclusion
In people with COPD, depression had a small negative relationship with PA irrespective of whether PA was measured by self-report or objectively. The relationship between anxiety and PA in people with COPD was moderated by PA measurement type, such that self-reported PA had a small negative relationship with anxiety and objectively measured PA had a small positive relationship. The results do not support targeting anxiety and depression to change physical activity in people with COPD.
| Abbreviations | ||
| COPD | = | chronic obstructive pulmonary disease |
| PA | = | physical activity |
| PR | = | pulmonary rehabilitation |
Disclosure statement
The authors report no conflict of interest.
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