Chronic obstructive pulmonary disease (COPD) is a group of pulmonary diseases characterized by persistent respiratory symptoms and airflow limitations (Global Initiative for Chronic Obstructive Lung Disease 2019). COPD includes different conditions: emphysema characterized by damage of the lung alveoli with air space enlargement, chronic bronchitis due to the destruction of bronchial tubes and cilia, and small airway disease presenting with a reduction in number and caliber of the small bronchioles (Silverman et al. 2018). Other obstructive lung diseases, such as bronchiectasis and asthma, share a few similarities with COPD; however, they present different pathophysiological processes, risk factors, symptoms, and treatments. Clinically, these pathogenic processes account for significant differences in signs and symptom presentation that affects disease management (Brusselle and Bracke 2014).

COPD has a high morbidity and mortality rate worldwide. Its prevalence in people aged 30 and over is 11.7% and it is constantly growing (Adeloye et al. 2015) due to the increasing number of tobacco smokers, environmental pollution, professional exposure to irritants, and life expectancy (Global Initiative for Chronic Obstructive Lung Disease 2019). COPD is the third cause of death worldwide (World Health Organization 2019). Moreover, COPD is one of the main causes of Emergency Department visits, hospital admissions and re-admissions, with total costs for health systems continuously increasing (World Health Organization 2019). In Europe alone, the cost of the treatment of COPD for healthcare systems is about 40 million euros per year, 3% of the total European budget (Chapman et al. 2006).

COPD presents physiological manifestations, such as dyspnea, cough, fatigue, and susceptibility to infections as well as psychological and emotional suffering (Global Initiative for Chronic Obstructive Lung Disease 2019). On this aspect, anxiety and depression are widely reported with a mean prevalence of 36% (range 6–74%) and 40% (8–80%), respectively (Yohannes et al. 2010). The psychological and emotional suffering, which is also triggered by physical causes, has a negative impact on the physiological status and on the perception of quality of life of those affected (Habraken et al. 2011). Beside pharmacological treatments, non-pharmacological interventions have been suggested to prevent and treat global distress in people suffering from COPD, including cognitive behavioral therapies (Baraniak and Sheffield 2011) and mindfulness-based programs (MBPs) (Harrison et al. 2016). Cognitive behavioral therapy focuses mainly on changing negative thoughts and behavioral activation, emphasizing the detection and the modification of maladaptive beliefs, whereas MBPs are centered on individuals’ psychological and emotional issues caused by the disease, promoting an active involvement with their thoughts, and the recognition and active acceptance of the disease in order to develop appropriate behaviors (Harrison et al. 2016).

The MBPs with the longest consolidated tradition and most robust evidence are the Mindfulness-Based Stress Reduction (MBSR) program and Mindfulness-Based Cognitive Therapy (MBCT) (Crane et al. 2017). The MBSR was created to reduce stress in people affected by chronic pain (Kabat-Zinn 1982) and has subsequently been applied to people with other medical conditions (Bohlmeijer et al. 2010). MBSR is aimed at developing mindfulness regarding the health conditions and at modifying the relationship with the disease, the automatic reactions and unwholesome habits, the judgment on themselves, and the inappropriate strategies that lead to increased distress. The MBSR protocol entails eight weekly classes, with each class lasting about two and a half hours, and daily individual practice at home. During the class, the individuals are guided to bring their attention, with a kind, non-judgmental attitude, on their bodies, their ways of breathing, their physical sensations, and their own feelings. Also, in the class, individuals are asked to share their experiences connected with the proposed practices with the group of peers, to create a body of shared experiences and lead to observations and comprehensions encouraged by the mindfulness instructor.

The MBCT, derived from the MBSR, was developed to prevent depressive relapse in people with depression (Segal et al. 2013) and subsequently has also been used to reduce depression and anxiety caused by other medical conditions (Cullen 2011; Sipe and Eisendrath 2012). Unlike MBSR, MBCT is aimed at changing the individuals’ identification with their own thoughts and how the thoughts act on their negative feelings (Kuyken et al. 2010). The MBCT is performed over eight weekly classes lasting 2 h, and it is a combination of mindfulness practices and mindful yoga similar to those proposed in MBSR protocol. Furthermore, cognitive therapy principles and exercises are taught through short theoretical lessons about the different aspects of mood disorders (Segal et al. 2013). Other MBPs have been derived from the traditional MBSR and MBCT and have been tailored to manage different psychological and physical health problems in specific populations; however, they are in earlier development stages, and research on their effectiveness is still scarce (Crane et al. 2017).

While there is evidence on the effectiveness of traditional MBPs in many chronic illnesses (Gotink et al. 2015; Leung et al. 2015; Noordali et al. 2017; Zhang et al. 2016), only a few studies have been conducted to test their effectiveness in COPD people. MBPs can be more appropriate for people with COPD than other psychosocial interventions as instead of modifying cognitions, they promote the modification of individual thoughts and an accepting mode of response, especially useful during dyspnea attacks and the associated anxiety that may occur (Baraniak and Sheffield 2011; Coventry et al. 2013). A literature review conducted to identify the effect of MBPs on people with respiratory disease, including asthma, respiratory failure, and COPD, found that, due to wide differences in the interventions and measured outcomes, no conclusion could be drawn on their effectiveness (Harrison et al. 2016). Another review, carried out to assess the effectiveness of different psychosocial interventions on health outcomes in people with COPD, reported an improvement in physical outcomes after mind-body interventions, but no specific sub-analysis for MBP on COPD was carried out (Farver-Vestergaard et al. 2015).

As in recent years, interest in the application of MBPs in COPD has increased, a systematic review is needed updating the latest evidence on the effectiveness of MBPs on health outcomes. However, addressing MBP effectiveness alone could lead to important information being missed on the experiences and perceptions of people involved in the interventions, on how and why the interventions achieve or do not achieve their effects, and what promotes or discourages people’s participation in the program. Such knowledge can be explored only through qualitative studies. A few qualitative studies have been conducted exploring the experience of MBPs from the point of view of COPD subjects, but, to our knowledge, they have never been summarized in a review.

Combining and integrating the qualitative and quantitative findings of studies on this topic could be useful to inform health-care professionals and researchers on what could encourage people with COPD to get involved in a MBP or prevent them from doing so, and on which benefits are to be expected from this kind of program. Thus, we conducted a mixed method review aiming (i) to identify and summarize the qualitative and quantitative evidence on the application of MBPs to people with COPD and (ii) to aggregate the qualitative and quantitative evidence to understand whether MBPs could be effective and appropriate in people with COPD and under which conditions and modes, describing favorable and unfavorable implementation factors.

Methods

Design

A mixed methods review was conducted following the Joanna Briggs Institute (JBI) methodology. This methodology allows a synthesis of quantitative and qualitative evidence to provide a better understanding of the phenomenon under study and to inform evidence-based practice (Lizarondo et al. 2017). A convergent segregated approach was used that entails a separate synthesis of the qualitative and quantitative studies, a conversion of the quantitative into qualitative data or qualitative into quantitative data, and then an aggregation of the findings to draw up recommendations to inform clinical practice and policy (Lizarondo et al. 2017). The JBI System for the Unified Management, Assessment and Review of Information (SUMARI) software was used to support the review process. The review protocol was registered on the international prospective register of systematic reviews (PROSPERO) (CRD 42018104818).

Search Strategy

A three-step search according to the JBI approach was conducted to retrieve all relevant studies. Firstly, a preliminary explorative research was performed on PubMed and PsycINFO to retrieve the most suitable keywords and thesaurus terms related to the phenomenon under study. Afterwards, a systematic research using the keywords and thesaurus terms identified was conducted on PubMed, CINAHL, EMBASE, PsycINFO, Web of Science, Scopus, the Joanna Briggs Institute evidence-based practice database, and the Cochrane Library. Lastly, the references of all identified papers were evaluated to identify further pertinent papers. No limits were set regarding the year of the study publication and the last research was performed October 28, 2019. The search was limited to papers in English, Italian, Spanish, or French published in peer-reviewed journals. Conference proceedings, theses, dissertations, and other unpublished literature were excluded from the research. The terms used were COPD, chronic obstructive pulmonary disease, chronic obstructive lung disease, mindfulness, mindfulness-based stress reduction, and mindfulness-based cognitive therapy. The search on the databases was conducted by a reviewer in collaboration with an expert librarian to ensure process rigor. The search strategies used in all the identified databases are illustrated in Online Resource Table S1.

Inclusion and Exclusion Criteria

Quantitative Study Review

Type of Patients

Studies considering people aged 18 years and over in which COPD was the principal diagnosis, as defined by Global Initiative for Chronic Obstructive Lung Disease (2019), at any disease stage, were included in our review. The severity of airflow limitations derived from the spirometric values is classified as mild (stage I), moderate (II), severe (III), and very severe (IV) COPD. People in whom the main diagnosis was another chronic lung disease, such as asthma, lung cancer, pulmonary hypertension, pulmonary fibrosis, bronchiectasis, were excluded, since these diseases are characterized by different age of onset, risk factors, etiology, symptoms, treatments, and psychological profiles, thus comprising heterogeneous populations. Including all these populations together would negatively affect the generalizability of results. Studies including individuals with different lung diseases were included if a subgroup analysis on a COPD sample was conducted, or if it was possible to extrapolate data from the COPD individuals. No limit was set to the presence/number of comorbidities.

Type of Interventions

Programs based on mindfulness, including MBSR and MBCT, following the traditional approach with a scheduled 8-week program were included (Crane et al. 2017). MBPs adapted specifically for people with COPD were also considered if they followed the key components of the traditional programs (Crane et al. 2017). Both face-to-face and tele-delivered programs were included. Other mind/body interventions, such as yoga and meditation, used as single components of the program, were excluded, as well as single short session of MBPs.

Type of Comparators

For experimental studies, the control intervention could consist of no treatment, or other types of treatment, such as pulmonary rehabilitation, support groups or any other type of mind-body practices.

Type of Outcomes

All the psychological and physiological health outcomes evaluated in the studies were considered, including but not limited to stress, anxiety, depression, quality of life, dyspnea, and other physiological and psychological variables.

Type of Studies

Randomized controlled trials (RCT), non-randomized controlled trials (nRCT), quasi-experimental studies, observational and descriptive studies were included.

Qualitative Study Review

Type of Patients

Besides the inclusion and exclusion criteria identified for the quantitative component of the review, papers including the experiences of other individuals, such as caregivers or healthcare professionals, were considered only if it was possible to extrapolate the findings related to people with COPD.

Phenomena of Interest

COPD people’s experiences, feelings, and perceptions about the MBPs, the influence of the programs on their life, their relationship with the disease, and their experiences with the mode of delivery of the MBP were considered. The MBPs could be by face-to-face, tele-delivered, or provided by any other mode.

Context

All healthcare settings in which the MBP could be provided were considered, including people with COPD from any country and ethnic group.

Type of Studies

All kinds of qualitative study designs, including but not limited to descriptive qualitative research, phenomenology, grounded theory, action research, ethnography, and mixed methods studies were included. In the case of mixed methods studies, the qualitative and quantitative components were analyzed separately and included in the qualitative and quantitative parts of the review, respectively.

Study Quality Appraisal

The methodological quality of qualitative and quantitative studies was assessed using the Critical Appraisal Tools (CATs) developed by JBI for the specific study design (Joanna Briggs Institute 2017). The CAT for RCT includes 13 criteria: (1) randomization of the treatment group, (2) allocation concealment, (3) baseline comparability among study groups, (4) participants’ blindness to treatment, (5) blindness to treatment delivery, (6) outcome assessor blindness, (7) same baseline treatment between groups, (8) follow-up analysis, (9) intention-to-treat analysis, (10) same outcome measure between groups, (11) reliable outcome measures, (12) appropriate statistical analysis, and (13) trial design. The CAT for quasi-experimental studies comprises nine criteria: (1) clear temporal relationship between variables investigated, (2) comparability of participants, (3) presence of other treatment/care other than the exposure, (4) presence of a control group, (5) outcome measurements pre- and post-intervention/exposure, (6) complete follow-up analysis, (7) outcomes measured in the same way between groups, (8) reliable outcome measures, and (9) appropriate statistical analysis. The CAT for descriptive studies includes eight criteria: (1) clear inclusion/exclusion criteria, (2) description of study subjects and setting, (3) valid and reliable exposure measurement, (4) objective criteria for condition measurement, (5) identification of confounding factors, (6) adjustment for confounding factors, (7) valid and reliable outcome measurement, and (8) appropriate statistical analysis.

The CAT for qualitative studies considers the following 10 criteria: the congruity between (1) philosophical perspective and research methodology, (2) methodology and aims, (3) methodology and data collection methods, (4) methodology and data analysis, and (5) methodology and interpretation of results. (6) Identification of the researcher’s location regarding theory, (7) identification of the mutual influence between the researcher and the research, (8) adequate representation of participants’ voices, (9) proof of conformity with ethical criteria, and (10) correct derivation of the conclusion from the results.

For the mixed methods research, each component of the study was assessed using the CAT corresponding to the design used. Two reviewers assessed separately the methodological quality of the studies. Any disagreement about quality assessment was solved by discussion. Studies that did not reach a score of 50% for the criteria for each CAT (e.g., 4 out 8 for CAT of descriptive studies) were considered of poor methodological quality and excluded. The results of the quality assessment of the studies are reported in Online Resource Table S2.

Data Extraction

Data on population characteristics, study design, aims, intervention characteristics, measures, and main results were extracted from the articles included. For the quantitative studies, the specific data extraction tool displayed in SUMARI was used, and likewise for the qualitative studies; for the qualitative and quantitative component, the data from mixed methods studies were extracted according to the appropriate JBI extraction tool. In qualitative studies, themes and categories were considered as results, while in quantitative studies, descriptive statistics, p values, and effect sizes for mean score differences were considered as results. Two reviewers independently extracted data and a third reviewer checked for accuracy of the data extraction.

Data Synthesis

For the quantitative findings, due to the heterogeneity of the study interventions, outcomes and measurements, no statistical meta-analysis pooling of the quantitative data was possible; therefore, quantitative results were reported in a narrative form and synthesized descriptively. For the qualitative findings, a meta-synthesis was undertaken according to JBI methodology. It encompassed a three-step process. Firstly, findings of the primary studies were rated according to their credibility. Only findings rated as unequivocal (meaning that there was no reasonable doubt that authors’ findings were supported by original data) and credible (findings were plausibly or could be logically inferred from study data) were included. Study findings assessed as unsupported (no identifiable relationship between findings and data could be found) were excluded (Joanna Briggs Institute 2017). Afterwards, findings were grouped to produce a preliminary set of findings, and aggregated in categories based on similarity in meaning. Lastly, categories were meta-aggregated to create a set of synthesized findings.

Summary of Findings

The results of the quantitative and qualitative components were then aggregated following the JBI mixed methods review methodology. Firstly, the quantitative findings were converted into a narrative form. The newly identified narrative results were then categorized and summarized to create sub-categories comparable with qualitative meta-synthesis findings. The sub-categories derived from the quantitative data were fit together with the qualitative meta-synthesis findings to generate a new set of synthesized findings organized as a set of recommendations or conclusions. Relationships and patterns between findings were traced, and the different sources of data were compared for critical data analysis.

Appraisal of Level of Evidence

The level of evidence for quantitative studies was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system (Ryan and Hill 2016), that rates evidence in four grades: very low, low, moderate and high. To rank the results, an a priori rank is assigned to all findings based on the study design from which they are derived and then downgraded based on the risk of bias, inconsistency, indirectness, imprecision and publication bias of the studies included. The ConQual system was used to establish the confidence for qualitative evidence (Munn et al. 2014). Similarly to the GRADE system, qualitative evidence is ranked as very low, low, moderate, and high. After an initial ranking based on the type of paper included, the level of confidence is downgraded considering the dependability (appropriateness of the conduct of the research with research aims and purpose) and the credibility (findings classified as unequivocal, credible, or unsupported included in the synthesized findings) of the results (Joanna Briggs Institute 2017).

Results

A total of 321 citations were retrieved from the search carried out from the eight databases. Two papers were identified through the references lists of the included papers. Of the 323 records identified, 174 papers were duplicated and therefore excluded. The remaining 149 papers retrieved were independently screened by two reviewers and 125 were excluded after reading the title and abstract. The 24 articles considered as relevant were read full-text to look for consistency against the review aims and inclusion/exclusion criteria. After full-text reading 16 papers were excluded because COPD was not the main diagnosis, they addressed not standardized MBPs, or were not research papers (a list of the excluded papers with reasons is presented in Online Resource Table S3). The inclusion of papers was discussed between reviewers and disagreement was solved by the consultation of a third independent reviewer. Eight articles were then evaluated for final inclusion. After quality appraisal, one study was excluded due to poor methodological quality, not reaching the minimum score in the specific CAT (Benzo 2013). Finally, seven papers were included in the review. The literature search process is described in Fig. 1.

Fig. 1
figure 1

Literature identification process

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Characteristics of the Studies and Participants

Five studies were reported in the seven articles, published between 2009 and 2018. Of the five studies, one study was conducted in the United Kingdom (Malpass et al. 2015; 2018), two in Denmark (Farver-Vestergaard et al. 2018a; b), and two studies, reported in three papers, were from the US (Chan et al. 2015; Chan and Lehto 2016; Mularski et al. 2009).

Of the included papers, three were quantitative (Chan et al. 2015; Farver-Vestergaard et al. 2018a; Mularski et al. 2009), two qualitative (Malpass et al. 2015; 2018), and two mixed methods studies (Chan and Lehto 2016; Farver-Vestergaard et al. 2018b). The two mixed methods studies contributed separately to both the quantitative and qualitative data synthesis. Regarding the quantitative studies, three studies were RCTs (Chan et al. 2015; Farver-Vestergaard et al. 2018a; Mularski et al. 2009), one a pre-post intervention (Farver-Vestergaard et al. 2018b), and one an observational component of a mixed methods study (Chan and Lehto 2016). Among the four qualitative studies, three papers used a qualitative descriptive approach (Chan and Lehto 2016; Farver-Vestergaard et al. 2018a; Malpass et al. 2018) and one study used a phenomenological design (Malpass et al. 2015), which is a qualitative research approach that focuses on the meaning attributed by people to their own lived experiences (Creswell 2013).

A total of 264 subjects affected by COPD were studied, 219 subjects in the quantitative component of the review (sample range 8–86) and 45 in the qualitative meta-synthesis (sample range 5–32). Sparse information about participants’ characteristics was reported. Most of the studies included male patients from moderate to very severe COPD, aged over 65; only a few studies reported the number of active smokers. All the studies were conducted in primary care settings.

Types of Mindfulness-Based Programs

In the studies identified, different MBPs were investigated. MBCT programs adapted to COPD were used in three studies. In one study, 8 weekly group meetings of 120 min each and 30 min of daily home practice were proposed, offering alternative meditation exercises to those based on breathing (Malpass et al. 2015; 2018). In another study the session time was reduced to 105 min as the program was provided as an add-on to a rehabilitation program (Farver-Vestergaard et al. 2018a). Finally, a tele-MBCT program was tested in one study consisting of eight weekly 120-min group-based videoconferences with daily home practice (Farver-Vestergaard et al. 2018b). Modified MBSR programs were used in the other two studies. In one study, the weekly class time was reduced to 60 min to take into consideration the fatigability of people with COPD, and a non-threatening focus on breath during the meditation exercises, together with Ujjayi breathing, QiGong, labyrinths and spiritual mantras were introduced into the program (Chan et al. 2015; Chan and Lehto 2016). Mularski et al. (2009) included relaxation training in the first 2 weeks of the standard 8-week MBSR program.

The MBPs were provided by trained mindfulness therapists (Malpass et al. 2018; 2015; Mularski et al. 2009), nurses (Chan et al. 2015; Chan and Lehto 2016), and clinical psychologists (Farver-Vestergaard et al. 2018a; b).

A detailed summary of the quantitative and qualitative studies included is presented in Table 1 and Table 2, respectively.

Table 1 Description of quantitative studies (in chronological order)
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Table 2 Qualitative included studies characteristics (in chronological order)
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Effectiveness of Mindfulness-Based Programs in COPD

In the RCTs identified, the effect of MBPs was evaluated on several health outcomes, including psychological, such as anxiety, sensitivity to anxiety, depression, stress, quality of life and level of mindfulness, as well as physiological outcomes, such as dyspnea and respiratory symptoms, functional limitations, number of exacerbations and inflammatory response of biomarkers. In these studies, the MBP was compared with a passive control group (waiting list) (Chan et al. 2015), or active control group, including pulmonary rehabilitation (Farver-Vestergaard et al. 2018a) and support groups (Mularski et al. 2009). The characteristics of people attending or not attending the programs and the reasons for dropping out were also investigated in these studies as well as in an observational component of a mixed methods study (Chan and Lehto 2016).

Effects on Anxiety

Two studies considered the effect on anxiety. No statistically significant reduction of patients’ anxiety was found in the groups following the MBPs (Farver-Vestergaard et al. 2018a; b). Also, no statistically significant effect on anxiety sensitivity, defined as the fear of anxiety-related sensations, was reported (Chan et al. 2015).

Effects on Depression

Among the two studies analyzing the effect on depression, only one study reported a statistically significant reduction of depressive symptoms in people attending a MBP associated to a pulmonary rehabilitation program, with greater depression reduction in younger people (Farver-Vestergaard et al. 2018a). No statistically significant effect on depression was found in the group treated with tele-delivered MBCT (Farver-Vestergaard et al. 2018b).

Effects on Stress

One study evaluated the effect on stress, reporting no reduction of its levels in the intervention group (Mularski et al. 2009).

Effects on Health-Related Quality of Life

Four studies assessed the effect of MBPs on health-related quality of life using general (Short Form-36), specific disease-related (COPD Assessment Test [CAT], St. George’s Respiratory Questionnaire [SGRQ], and Chronic Respiratory Questionnaire [CRQ]), and symptom-related measurements (Memorial Symptom Assessment Scale [MSAS]). No statistically significant effect on quality of life was found (Chan et al. 2015; Farver-Vestergaard et al. 2018a; b; Mularski et al. 2009), except for the improvement of the management of emotions measured by CRQ in people with COPD attending more than six sessions of the MBP (Chan et al. 2015).

Effects on Level of Mindfulness

Two studies investigated increase in the level of mindfulness acquired through the practice of mindfulness, using two different instruments, the Freiburg Mindfulness Inventory (Chan et al. 2015) and the 5-Factor Mindfulness Questionnaire (Mularski et al. 2009), but no statistically significant modifications were found in the intervention group.

Effects on Respiratory Symptoms and Pulmonary Function

Two RCTs tested the effect of mindfulness on the patients’ respiratory symptoms and pulmonary function, assessing dyspnea through the modified Borg scale or breathing parameters through a plethysmograph. The effectiveness of MBPs was not supported (Chan et al. 2015; Mularski et al. 2009).

Effects on Functional Limitations

Daily physical activities and movement limitations were assessed in two studies using the triaxial accelerometer or the 6-min walk test, and no modifications were reported in people attending the programs (Farver-Vestergaard et al. 2018a; Mularski et al. 2009).

Effects on Exacerbations and Markers of Inflammation

One study assessed the possible influence of MBPs on the occurrence of exacerbations showing no effect (Mularski et al. 2009). Another study explored the effect on pro-inflammatory cytokine response and found no modification induced by MBP (Farver-Vestergaard et al. 2018a).

Program Attendance and Dropout

Rates of attendance to mindfulness classes and dropouts were evaluated in all studies. Dropout rates varied from 37% (Chan et al. 2015) to 48% (Mularski et al. 2009), except for the tele-delivered program where all the eight participants completed the program (Farver-Vestergaard et al. 2018b). The main reasons for not completing the program or skipping classes were: the worsening of participants’ health conditions (Chan et al. 2015; Mularski et al. 2009); personal and family commitments not compatible with the time required for the program attendance and the daily home practice (Chan et al. 2015; Chan and Lehto 2016; Farver-Vestergaard et al. 2018a; Mularski et al. 2009); perception of weirdness and unhelpfulness of the MBPs (Chan and Lehto 2016; Mularski et al. 2009). Practical issues, such as difficulty in reaching the site where the program was delivered (Mularski et al. 2009), lack of motivation, and the programs perceived as too physically demanding were also reported as reasons for non-attending (Farver-Vestergaard et al. 2018a).

Meta-synthesis

From the four qualitative papers included in the review, 29 study findings were extracted. Two study findings were excluded as they did not address COPD subjects. The remaining findings were classified as unequivocal or credible (see Online Resource Table S4). The 27 study findings were aggregated in 14 categories that were merged into the following four synthesized findings: (1) people with COPD perceive that mindfulness-based programs improve their psychological and emotional well-being; (2) people with COPD perceive that mindfulness can promote a sense of control over physical manifestations of the disease; (3) people with COPD can present cultural, practical, and psychological barriers against practicing mindfulness; and (4) the modes of delivery of the mindfulness-based program can influence participation in and adherence to the practice by people with COPD (Table 3).

Table 3 Synthesized findings, categories, and findings extracted from the included studies
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People with COPD Perceive That Mindfulness-Based Programs Improve Their Psychological and Emotional Well-being

MBPs were perceived by people affected by COPD as helpful in improving their psychological and emotional well-being, leading to a reduction of the manifestation of distress and difficult emotions linked to the disease, such as stress and anxiety, and an increased ability to cope with them (Chan and Lehto 2016). Also, they report that mindfulness practice helped them to develop a feeling of compassion towards themselves as well as towards other people (Chan and Lehto 2016). Moreover, they believed that mindfulness promoted active acceptance of their disease (Chan and Lehto 2016; Farver-Vestergaard et al. 2018b; Malpass et al. 2015). The coping skills acquired through mindfulness practice also contributed to improve their perception of mental and emotional well-being (Chan and Lehto 2016; Malpass et al. 2015).

People with COPD Perceive That Mindfulness Can Promote a Sense of Control over Physical Manifestations of the Disease

People with COPD reported that mindfulness helped them to feel less burdened and threatened by their breathing difficulties, resulting in a general benefit. The practice of mindfulness was perceived as useful in providing tools to control respiratory issues and improve dyspnea management (Chan and Lehto 2016; Farver-Vestergaard et al. 2018b; Malpass et al. 2015). Furthermore, they reported that MBP improved the awareness of their physical sensations and helped them promptly identify signs and symptoms of dyspnea and to reduce the trigger of negative emotions, resulting in an improvement of the management of acute events (Farver-Vestergaard et al. 2018b; Malpass et al. 2015; Malpass et al. 2018). People stated that mindfulness training helped them remove the psychological barriers that impeded them from performing physical activities, such as walking for long distances (Malpass et al. 2015).

People with COPD Can Present Cultural, Practical, and Psychological Barriers Against Practicing Mindfulness

People with COPD described different factors that could hamper attendance at mindfulness classes and the daily practice at home. The practice of mindfulness could elicit negative emotions in people with COPD, such as feelings of guilt or connections with past unresolved issues (Chan and Lehto 2016). Also, they could present cultural preconceptions against mind/body practice or non-pharmacological complementary treatments in general, questioning the real effectiveness or usefulness of MBPs (Chan and Lehto 2016). Some people reported having developed this skepticism during the course of the program, due to the lack of the immediate results they had expected, or to their perception of not being able to meditate correctly, and for this reason they gradually abandoned the classes (Chan and Lehto 2016). Moreover, patients reported difficulties in reproducing at home the practices proposed during the group sessions, increasing their sense of inadequacy and frustration, and leading them to believe they were wasting their time, and to consider mindfulness useless outside of the class (Chan and Lehto 2016). The mindfulness practice also could interfere with their personal and family commitments, leading them to postpone or interrupt the practice or the classes (Chan and Lehto 2016).

The Modes of Delivery the Mindfulness-Based Program Can Influence Participation in and Adherence to the Practice by People with COPD

People with COPD reported that the ways the MBP was offered, and its conditions, could encourage or discourage the attending of mindfulness classes. They believed, for example, that offering a MBP together with a pulmonary rehabilitation program could promote participation in and acceptance of the mindfulness program as well as improving the mastery of the breathing exercises taught in the rehabilitation program (Malpass et al. 2015). The duration of each mindfulness class (120-min) and the length of the whole program (8 weeks) could present obstacles to complete attendance (Malpass et al. 2015). People with COPD believed that web-based MBPs could improve class participation and adherence to practice. The possibility of remaining at home, but at the same time being in contact with other people was greatly appreciated (Farver-Vestergaard et al. 2018b). On the other hand, due to technical problems occurring during the sessions, people often perceived a disturbed interaction with instructors and other people in the group that impeded the creation of a trusting atmosphere (Farver-Vestergaard et al. 2018b). For the creation of such atmosphere, some people preferred a program delivered face-to-face with direct interaction between instructor and other participants, to contact mediated by technology (Farver-Vestergaard et al. 2018b). Lastly, people with COPD appreciated the pratice of re-directing attention from their chest to another part of the body, since focusing on their breathing could intensify their experience of disconfort (Malpass et al. 2018).

Level of Evidence

The quality of evidence informing the outcomes of the experimental and quasi-experimental studies was assessed using the GRADE system. All outcomes received a ranking of ‘very low’ or ‘low’ level of evidence due to risk of bias, insufficient sample size to meet optimal information size in the studies considered; and, in the case of depression, due to a statistical heterogeneity between positive and negative treatment effects (Table 4). The quality of evidence for three synthesized findings assessed using the ConQual grading system received moderate ranking due to the downgrading of the dependability criterion by one level, and one synthesized finding was ranked low due to the downgrading of the dependability and credibility criteria (Table 4).

Table 4 Summary of grade of evidence derived from quantitative findings and qualitative synthesis
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Mixed Methods Synthesis

A single study with a very low level of evidence showed the effect of a MBP incorporated in a pulmonary rehabilitation program on depressive symptoms, especially in younger people. No evidence of measurable changes in the level of anxiety, stress, respiratory functions and other physiological outcomes was found. Thus, to date, no recommendation on the use of MBPs could be derived. Despite the absence of evidence of the effectiveness of MBPs, people with COPD attending the programs perceived that mindfulness gives them greater sense of control over the psychological, emotional and physiological manifestations of the disease. Participation in and completion of the MBP appeared to be particularly challenging due to several cultural, practical, and psychological obstacles, such as prejudices against mindfulness, interference with personal and family commitments and difficulty in practicing mindfulness. Furthermore, the characteristics of the mindfulness-based protocols and the different conditions of the specific program and modes of delivery could impede or encourage program attendance. In particular, the length of the 2-month programs and 120-min classes could hamper the attendance of people with unstable health conditions and functional limitations due to the long-term commitment and the effort of traveling to the sites where the program is offered. MBPs delivered via the web seem more favorable to facilitating participation by people with COPD.

Discussion

The present mixed methods review synthesized and combined quantitative evidence on the effectiveness of MBPs with qualitative evidence on the experiences of mindfulness practice in people affected by COPD. MBPs were developed to help people manage their psychological issues and their emotional self-regulation (Tang and Leve 2016). These programs have also been proposed to reduce the repercussions of chronic illnesses at the psychological and emotional level, which can lead to distress, anxiety and depression (Demarzo et al. 2015). Indirect positive effects on physiological outcomes are also expected, as psychological and emotional distress can influence physiological functions.

Previous literature has shown conflicting evidence on the effectiveness of MBPs on psychological and physiological outcomes in chronic conditions (Abbott et al. 2014; Lauche et al. 2013; Simpson et al. 2014; Veehof et al. 2016) and in respiratory diseases in particular (Harrison et al. 2016). In our review, no evidence was found of reduction of anxiety levels in people with COPD. Only a single randomized clinical trial showed that a MBP added to pulmonary rehabilitation was associated with reduced depression score compared to pulmonary rehabilitation alone, but the MBP was not associated with any improvement in other outcomes (Farver-Vestergaard et al. 2018a). Despite the increased interest in MBPs, our review showed that the number of RCT studying the effects of MBPs in the COPD population is surprisingly low. This could be due to the difficulty in recruiting this population and obtaining long-term participation in the program. Further research with large samples should be conducted to reveal the effectiveness of MBPs on COPD as well to compare the effects of MBPs on different chronic lung diseases, such as asthma and bronchiectasis. Also, further research comparing short and long interventions is needed in order to understand the benefits of MBPs of different lengths for COPD people.

In the qualitative studies identified in our review, a few participants reported to perceive some benefit from mindfulness practice on anxiety, stress and breathlessness. In people with COPD, anxiety and dyspnea are strictly interconnected as an episode of dyspnea can generate anxiety and anxiety can increase breathlessness (Coventry et al. 2013). This favorable perception could be explained as mindfulness training permits people with COPD to recognize the signs of dyspnea promptly and develop an ability to stay in the present moment, which leads to a disidentification from the strong emotions that occur with an improvement in the capacity to manage the breathlessness, facilitating a return to normal breathing (Pooler and Beech 2014). Common instruments used to measure anxiety, even if well validated, might not capture such modifications on level of anxiety. The symptoms of anxiety are heterogeneous and variable over the time, and in people with a chronic disease, symptoms of anxiety can overlap with those of people with anxiety disorders (Rose and Devine 2014). For this reason, qualitative evidence could be more sensitive in capturing these emotional manifestations than objective instruments. Future research should consider combining subjective experiences with objective instruments in order to measure more accurately the changes in anxiety symptoms (Bandelow et al. 2017). The absence of measurable effects on pulmonary function assessed through respiratory parameters after participation in an MBP can be justified by the fact that the level of airway obstruction in COPD is not modifiable, but mindfulness practice can help people implement different ways of responding to dyspnea events, deactivating the vicious circle dyspnea-anxiety-dyspnea (Hartley and Phelps 2012).

The appreciation of MBPs on the part of people with COPD, in the absence of evidence supporting their effectiveness, can also derive from the mental predisposition of the people attending the course. Malpass et al. (2015) noticed that the ability to be mindful was not influenced by the number of sessions attended by participants. This reinforces the idea that mindfulness practice is more suitable for people with a natural predisposition to meditation and introspection. In the studies identified in our review, participants reported that they did not understand what mindfulness really was or had preconceptions towards mindfulness. Understanding what people think about mindfulness before program implementation could offer to researchers the opportunity to provide more appropriate information about MBPs to increase people’s participation (Harrison et al. 2017).

One of the most problematic issues in the RCTs identified in our review was the small sample sizes and higher dropout rates that reduced their statistical power. Several personal barriers led people to drop out from or limit attendance at mindfulness classes. The most frequently reported one was the big investment of time required by the weekly sessions and the daily mindfulness practice at home. Consequently, shorter MBPs could lead to higher participation rates and adherence to practice sessions. There is evidence that even a brief mindfulness practice of at least 10 min can change underlying brain processes (Moore et al. 2012). Although shorter programs could be more easily accepted by individuals with chronic conditions, longer guidance would always be necessary to support the regular daily practice (Howarth et al. 2016). Home support for people with COPD, who are usually old, with a high comorbidity and exacerbation rate, can help them maintain mindfulness practice over time. Even though shorter programs could be more feasible and acceptable, they might be less effective, particularly in improving long-term outcomes, such as self-management, in people with long-term conditions (Gawande et al. 2019). Self-management is of great interest in COPD, since it could improve health-related quality of life, dyspnea, and reduce hospital admissions (Zwerink et al. 2014). Studies should be conducted to assess the long-term effects of mindfulness, as well as studies evaluating different modes of mindfulness implementation, such as apps for promoting mindfulness based on evidence-based framework (Owens et al. 2018).

Furthermore, it could be useful to consider the best timing for proposing MBPs. Individuals with COPD after an exacerbation could be more motivated to participate in MBPs and consequently obtain greater benefits from their participation (Jin et al. 2008). Also, a MBP could be a meaningful addition at a pulmonary rehabilitation program, as patients after an exacerbation could find the physical exercises challenging; thus, MBPs could help to increase pulmonary rehabilitation success (Puhan and Lareau 2014). It is also important to identify the right outcome at the right time-point: for example, stress reduction could be a more appropriate outcome immediately after an exacerbation, whereas depression decrease could be achievable in a more stable phase of the disease.

In the studies included, no distinction was made between individuals with COPD that were tobacco smokers (actual or former) and those who had never smoked, and thus, no information on the effects of MBPs on the smoker COPD population could be derived. Tobacco smokers present different psychological profiles and lower self-regulation with respect to non-smokers, and thus MBPs could have different effects on these two populations. Research has showed, for example, that mindfulness training is able to increase long-term abstinence rates in smokers (Oikonomou et al. 2017). Further research could be relevant to understand if COPD tobacco smokers are those with a lower retention rate in the programs, and are more willing to attend short programs due to their higher impulsivity.

It is important to point out that modified versions of MBSR and MBCT standard protocols were used in the programs comprised in this review. The heterogeneity of the programs investigated and the different adaptations of the original protocols to COPD prevent any direct comparison of one intervention with another. In addition, the changes made to the protocols have not led to the hoped-for effects. People have often criticized the length of the original protocol, but the changes made often meant a further increase in the length or burden of the session, as, for example, joining an MBP session onto pulmonary rehabilitation sessions (Farver-Vestergaard et al. 2018a). Further studies should be done, comparing these modified protocols with the original MBSR and MBCT protocols, and investigating which protocols are most suitable for this population.

This review has some limitations. First, the studies identified were conducted in the US and Northern Europe, limiting the generalizability of our results to other countries. Secondly, due to the limitations of the databases screened and languages selected, papers offering further results could have been excluded. The mutual influence between dyspnea and psychological and emotional status was not evaluated in some of the studies included and, when assessed, these two factors were investigated separately. For this reason, it was not possible to determine the connection between mindfulness and the psychosomatic aspects of COPD.

This systematic review showed that there is no evidence of effectiveness of MBPs in people suffering from COPD. Several conditions can obstacles the implementation and the attendance of MBPs. Further methodologically sound studies with bigger sample sizes and with coherent outcome measures are needed to verify the effectiveness of mindfulness in COPD populations as well as further qualitative studies, to understand the experiences of people with COPD attending MBPs. Due to fluctuations in COPD symptoms and difficulties in leaving the house, alternative modes of offering mindfulness training, such as shorter overall program duration, or the duration of each session, and web-based formats, should be tested to facilitate attendance at the program. Moreover, follow-ups could be introduced to help people with COPD to maintain mindfulness practice over time and promote MBPs effectiveness.