- We found that people with asthma who take part in supervised programmes of exercise and education (known as pulmonary rehabilitation) are likely to get fitter (can walk further) and have better wellbeing immediately after completing these programmes compared to those who receive usual care. However, we are not certain if these benefits persist up to one year later.
- Due to a lack of evidence, the effects of pulmonary rehabilitation on outcomes such as rates of asthma attacks or hospitalisations, anxiety and depression, or physical activity levels is unclear.
- Larger, well-designed studies are needed to better estimate the true benefit of pulmonary rehabilitation for adults with asthma.
What is asthma?
Asthma is a common lung disease where the breathing tubes can become inflamed and narrowed and may produce extra mucus. People with asthma can experience cough, wheezing, chest tightness, and breathlessness, with those most severely affected experiencing difficulty going about their everyday lives.
Asthma cannot be cured, but symptoms can be controlled. Different medications can help keep symptoms under control, whilst physical exercise can also help. However, some people with asthma may find it challenging to undertake comprehensive exercise programmes.
What is pulmonary rehabilitation?
Supervised programmes of exercise and education (called pulmonary rehabilitation) are commonly used for people with chronic lung conditions and help improve breathing, fitness, and wellbeing. These programmes may be based at hospitals, outpatient clinics, or even at home.
Pulmonary rehabilitation is a recommended standard of care for many chronic lung conditions; however, its effects in adults with asthma are less clear.
What did we want to find out?
We wanted to see how pulmonary rehabilitation affects physical fitness, control of asthma symptoms, and wellbeing of adults with asthma compared to usual clinical care involving no pulmonary rehabilitation. We also wanted to learn how it affects the rate of severe asthma attacks/hospitalisations, mental health (anxiety and depression), muscle strength, physical activity levels, and markers of inflammation (in sputum or blood). Finally, we wanted to see whether it is associated with any unwanted effects.
What did we do?
We searched for studies that compared pulmonary rehabilitation to usual care in adults with asthma. Treatment must have lasted at least four weeks (or eight or more sessions) and must have included aerobic exercises (such as walking or cycling) and education or self-management.
We compared and summarised findings across all eligible studies and rated our confidence in the evidence based on factors such as study methods and size.
What did we find?
- We found 10 studies involving 894 adults with asthma.
- The studies ranged in size from 24 to 412 people.
- Most studies were conducted in Europe.
- Where reported, most study participants were female, with the average age ranging from 27 to 54 years.
- One study specifically included people with severe forms of asthma. Another study specifically included people who had a condition involving overlapping features of both asthma and chronic obstructive pulmonary disease (COPD).
- The way pulmonary rehabilitation was delivered varied across studies. Inpatient programmes lasted 3 to 4 weeks, whilst outpatient programmes lasted 8 to 12 weeks.
- The specific nature of exercise or education components amongst the included studies varied widely.
- Pulmonary rehabilitation probably causes a large increase in physical fitness immediately after completion of the programme, resulting in an ability to walk an average of 80 metres further in 6 minutes than in people who receive usual care. There may be little to no effect on physical fitness measured up to one year later.
- Pulmonary rehabilitation may result in small improvements in or little to no impact on asthma control immediately after completion of the programme or up to one year later compared to usual care.
- Pulmonary rehabilitation probably causes a large improvement in wellbeing as measured by the St George’s Respiratory Disease Questionnaire immediately after completion of the programme. Results may differ slightly according to different quality of life instruments. The effects potentially last up to one year, but results are very uncertain.
- Little to no effect on wellbeing was observed after programme completion or up to nine months follow-up when the Asthma Quality of Life Questionnaire was used.
- There was very limited evidence to determine the effect of pulmonary rehabilitation on rates of asthma attacks/hospitalisations, measures of anxiety and depression, limb muscle strength, levels of physical activity, or markers of inflammation in the blood or sputum.
- Data from one study suggested pulmonary rehabilitation resulted in no direct unwanted or harmful effects.
Limitations of the evidence
Our confidence in the evidence relating to outcomes such as physical fitness, wellbeing, and asthma control is limited due to concerns regarding unclear methods in some studies, the potential for participants or assessors (or both) to have influenced outcomes due to the awareness of assigned treatments, and the varied ways in which pulmonary rehabilitation was delivered.
The evidence is up-to-date to May 2021.
Moderate certainty evidence shows that pulmonary rehabilitation is probably associated with clinically meaningful improvements in functional exercise capacity and quality of life upon programme completion in adults with asthma. The certainty of evidence relating to maximal exercise capacity was very low to low. Pulmonary rehabilitation appears to confer minimal effect on asthma control, although the certainty of evidence is very low to low. Unclear reporting of study methods and small sample sizes limits our certainty in the overall body of evidence, whilst heterogenous study designs and interventions likely contribute to inconsistent findings across clinical outcomes and studies. There remains considerable scope for future research.
Asthma is a respiratory disease characterised by variable airflow limitation and the presence of respiratory symptoms including wheeze, chest tightness, cough and/or dyspnoea. Exercise training is beneficial for people with asthma; however, the response to conventional models of pulmonary rehabilitation is less clear.
To evaluate, in adults with asthma, the effectiveness of pulmonary rehabilitation compared to usual care on exercise performance, asthma control, and quality of life (co-primary outcomes), incidence of severe asthma exacerbations/hospitalisations, mental health, muscle strength, physical activity levels, inflammatory biomarkers, and adverse events.
We identified studies from the Cochrane Airways Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform, from their inception to May 2021, as well as the reference lists of all primary studies and review articles.
We included randomised controlled trials in which pulmonary rehabilitation was compared to usual care in adults with asthma. Pulmonary rehabilitation must have included a minimum of four weeks (or eight sessions) aerobic training and education or self-management. Co-interventions were permitted; however, exercise training alone was not.
Following the use of Cochrane's Screen4Me workflow, two review authors independently screened and selected trials for inclusion, extracted study characteristics and outcome data, and assessed risk of bias using the Cochrane risk of bias tool. We contacted study authors to retrieve missing data. We calculated between-group effects via mean differences (MD) or standardised mean differences (SMD) using a random-effects model. We evaluated the certainty of evidence using GRADE methodology.
We included 10 studies involving 894 participants (range 24 to 412 participants (n = 2 studies involving n > 100, one contributing to meta-analysis), mean age range 27 to 54 years). We identified one ongoing study and three studies awaiting classification. One study was synthesised narratively, and another involved participants specifically with asthma-COPD overlap. Most programmes were outpatient-based, lasting from three to four weeks (inpatient) or eight to 12 weeks (outpatient). Education or self-management components included breathing retraining and relaxation, nutritional advice and psychological counselling. One programme was specifically tailored for people with severe asthma.
Pulmonary rehabilitation compared to usual care may increase maximal oxygen uptake (VO2 max) after programme completion, but the evidence is very uncertain for data derived using mL/kg/min (MD between groups of 3.63 mL/kg/min, 95% confidence interval (CI) 1.48 to 5.77; 3 studies; n = 129) and uncertain for data derived from % predicted VO2 max (MD 14.88%, 95% CI 9.66 to 20.1%; 2 studies; n = 60). The evidence is very uncertain about the effects of pulmonary rehabilitation compared to usual care on incremental shuttle walk test distance (MD between groups 74.0 metres, 95% CI 26.4 to 121.4; 1 study; n = 30). Pulmonary rehabilitation may have little to no effect on VO2 max at longer-term follow up (9 to 12 months), but the evidence is very uncertain (MD −0.69 mL/kg/min, 95% CI −4.79 to 3.42; I2 = 49%; 3 studies; n = 66).
Pulmonary rehabilitation likely improves functional exercise capacity as measured by 6-minute walk distance, with MD between groups after programme completion of 79.8 metres (95% CI 66.5 to 93.1; 5 studies; n = 529; moderate certainty evidence). This magnitude of mean change exceeds the minimally clinically important difference (MCID) threshold for people with chronic respiratory disease. The evidence is very uncertain about the longer-term effects one year after pulmonary rehabilitation for this outcome (MD 52.29 metres, 95% CI 0.7 to 103.88; 2 studies; n = 42).
Pulmonary rehabilitation may result in a small improvement in asthma control compared to usual care as measured by Asthma Control Questionnaire (ACQ), with an MD between groups of −0.46 (95% CI −0.76 to −0.17; 2 studies; n = 93; low certainty evidence); however, data derived from the Asthma Control Test were very uncertain (MD between groups 3.34, 95% CI −2.32 to 9.01; 2 studies; n = 442). The ACQ finding approximates the MCID of 0.5 points. Pulmonary rehabilitation results in little to no difference in asthma control as measured by ACQ at nine to 12 months follow-up (MD 0.09, 95% CI −0.35 to 0.53; 2 studies; n = 48; low certainty evidence).
Pulmonary rehabilitation likely results in a large improvement in quality of life as assessed by the St George's Respiratory Questionnaire (SGRQ) total score (MD −18.51, 95% CI −20.77 to −16.25; 2 studies; n = 440; moderate certainty evidence), with this magnitude of change exceeding the MCID. However, pulmonary rehabilitation may have little to no effect on Asthma Quality of Life Questionnaire (AQLQ) total scores, with the evidence being very uncertain (MD 0.87, 95% CI −0.13 to 1.86; 2 studies; n = 442). Longer-term follow-up data suggested improvements in quality of life may occur as measured by SGRQ (MD −13.4, 95% CI −15.93 to −10.88; 2 studies; n = 430) but not AQLQ (MD 0.58, 95% CI −0.23 to 1.38; 2 studies; n = 435); however, the evidence is very uncertain.
One study reported no difference between groups in the proportion of participants who experienced an asthma exacerbation during the intervention period. Data from one study suggest adverse events attributable to the intervention are rare.
Overall risk of bias was most commonly impacted by performance bias attributed to a lack of participant blinding to knowledge of the intervention. This is inherently challenging to overcome in rehabilitation studies.