Review question
We reviewed the evidence about whether physical activity interventions (including exercise) have any effect on exercise capacity, health-related quality of life and lung function in people with cystic fibrosis (CF). This is an update of a previously published review.
Background
CF affects many systems in the body, but mainly the lungs. It causes shortness of breath and limits the amount of exercise people with CF can tolerate. The progress of lung disease leads to a low ability to exercise and to physical inactivity, which in turn affects health and health-related quality of life. We looked for studies where people with CF engaged in a physical activity intervention (including endurance-type activities such as walking, jogging, swimming and cycling; or resistance training; or combinations of both) compared to a control group with no intervention (usual care).
Search date
The evidence is current to 3 March 2022.
Study characteristics
We included 24 studies (875 participants) in this review. The number of people in each study ranged from nine to 117. Some studies included only children, others only adults, and some both children and adults. The studies included people with a wide range of disease severity. The studies used differing levels of supervision in their active training programmes: in 12 studies, participants were supervised; in 11 studies, participants were partially supervised; and in one study, participants were not supervised at all. The active training programme lasted up to and including six months in 14 studies, and longer than six months in the remaining 10 studies. Of the 24 included studies, seven added on a follow-up period (when all participants reverted to usual care, but were still allowed to exercise if they wished). The quality of the included studies varied widely.
Key results
This systematic review shows that physical activity interventions for longer than six months probably improve exercise capacity in people with CF. When compared with no activity, physical activity interventions may make little or no difference to lung function and health-related quality of life.
The largest study included in this review (117 participants) reported:
- no differences between the physical activity and control groups in the number of pulmonary exacerbations (a flare up of disease) (high-certainty evidence);
- no differences in the time to the first flare up for 12 months (high-certainty evidence);
- no beneficial effects of physical activity on diabetic control after nine months (moderate-certainty evidence).
Two studies (156 participants) found no differences between groups in the number of reported adverse events (low-certainty evidence).
For active training programmes lasting up to and including six months, the effects were similar to the longer programmes.
Only three studies which added a follow-up period (of varying durations) reported data we could analyse on changes in exercise capacity and lung function; and only one reported on quality of life. These results must be interpreted with caution.
Overall and when compared to usual care (no intervention), physical activity and exercise training probably lead to slightly better exercise capacity, while they may have little or no effect on lung function and health-related quality of life in people with CF.
Certainty of the evidence
We included 24 studies. Given the differences in effects across studies, the wide variation in study quality and the lack of information on clinically meaningful changes for several outcome measures, we consider the overall certainty of the evidence on the effects of physical activity interventions on exercise capacity, lung function and health-related quality of life as low to moderate. We are uncertain about the effects we have seen and better-quality studies will likely change these findings.
Factors affecting our certainty included that, in five studies, the characteristics of some of the people taking part were different between groups at the start of the studies, despite people being put into the different treatment groups at random.
Also, when comparing physical activity interventions to no intervention, people will always know which group they are in. However, we do not think the fact that people knew which treatment they were receiving would affect the results for lung function, as long as the assessments were done properly. In contrast, some bias may be introduced when investigators assessing a person's exercise capacity know to which group the person belongs. Investigators tried to prevent the outcome assessors from knowing to which groups the participants belonged in 10 included studies.
Selective reporting of results may also be an issue, especially as most of the included studies were not listed in trial registries, where details of the outcomes are reported.
Physical activity interventions for six months and longer likely improve exercise capacity when compared to no training (moderate-certainty evidence). Current evidence shows little or no effect on lung function and HRQoL (low-certainty evidence). Over recent decades, physical activity has gained increasing interest and is already part of multidisciplinary care offered to most people with CF. Adverse effects of physical activity appear rare and there is no reason to actively discourage regular physical activity and exercise. The benefits of including physical activity in an individual's regular care may be influenced by the type and duration of the activity programme as well as individual preferences for and barriers to physical activity. Further high-quality and sufficiently-sized studies are needed to comprehensively assess the benefits of physical activity and exercise in people with CF, particularly in the new era of CF medicine.
Physical activity (including exercise) may form an important part of regular care for people with cystic fibrosis (CF). This is an update of a previously published review.
To assess the effects of physical activity interventions on exercise capacity by peak oxygen uptake, lung function by forced expiratory volume in one second (FEV1), health-related quality of life (HRQoL) and further important patient-relevant outcomes in people with cystic fibrosis (CF).
We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. The most recent search was on 3 March 2022. We also searched two ongoing trials registers: clinicaltrials.gov, most recently on 4 March 2022; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), most recently on 16 March 2022.
We included all randomised controlled trials (RCTs) and quasi-RCTs comparing physical activity interventions of any type and a minimum intervention duration of two weeks with conventional care (no physical activity intervention) in people with CF.
Two review authors independently selected RCTs for inclusion, assessed methodological quality and extracted data. We assessed the certainty of the evidence using GRADE.
We included 24 parallel RCTs (875 participants). The number of participants in the studies ranged from nine to 117, with a wide range of disease severity. The studies' age demographics varied: in two studies, all participants were adults; in 13 studies, participants were 18 years and younger; in one study, participants were 15 years and older; in one study, participants were 12 years and older; and seven studies included all age ranges. The active training programme lasted up to and including six months in 14 studies, and longer than six months in the remaining 10 studies. Of the 24 included studies, seven implemented a follow-up period (when supervision was withdrawn, but participants were still allowed to exercise) ranging from one to 12 months. Studies employed differing levels of supervision: in 12 studies, training was supervised; in 11 studies, it was partially supervised; and in one study, training was unsupervised. The quality of the included studies varied widely.
This Cochrane Review shows that, in studies with an active training programme lasting over six months in people with CF, physical activity probably has a positive effect on exercise capacity when compared to no physical activity (usual care) (mean difference (MD) 1.60, 95% confidence interval (CI) 0.16 to 3.05; 6 RCTs, 348 participants; moderate-certainty evidence). The magnitude of improvement in exercise capacity is interpreted as small, although study results were heterogeneous. Physical activity interventions may have no effect on lung function (forced expiratory volume in one second (FEV1) % predicted) (MD 2.41, 95% CI ‒0.49 to 5.31; 6 RCTs, 367 participants), HRQoL physical functioning (MD 2.19, 95% CI ‒3.42 to 7.80; 4 RCTs, 247 participants) and HRQoL respiratory domain (MD ‒0.05, 95% CI ‒3.61 to 3.51; 4 RCTs, 251 participants) at six months and longer (low-certainty evidence). One study (117 participants) reported no differences between the physical activity and control groups in the number of participants experiencing a pulmonary exacerbation by six months (incidence rate ratio 1.28, 95% CI 0.85 to 1.94) or in the time to first exacerbation over 12 months (hazard ratio 1.34, 95% CI 0.65 to 2.80) (both high-certainty evidence); and no effects of physical activity on diabetic control (after 1 hour: MD ‒0.04 mmol/L, 95% CI ‒1.11 to 1.03; 67 participants; after 2 hours: MD ‒0.44 mmol/L, 95% CI ‒1.43 to 0.55; 81 participants; moderate-certainty evidence). We found no difference between groups in the number of adverse events over six months (odds ratio 6.22, 95% CI 0.72 to 53.40; 2 RCTs, 156 participants; low-certainty evidence).
For other time points (up to and including six months and during a follow-up period with no active intervention), the effects of physical activity versus control were similar to those reported for the outcomes above. However, only three out of seven studies adding a follow-up period with no active intervention (ranging between one and 12 months) reported on the primary outcomes of changes in exercise capacity and lung function, and one on HRQoL. These data must be interpreted with caution. Altogether, given the heterogeneity of effects across studies, the wide variation in study quality and lack of information on clinically meaningful changes for several outcome measures, we consider the overall certainty of evidence on the effects of physical activity interventions on exercise capacity, lung function and HRQoL to be low to moderate.