Exercise training for dust-related respiratory diseases

Research question
Exposure to harmful dusts or particles (such as asbestos), which may occur at work or outside of the work setting, can lead to respiratory diseases. These are called dust-related respiratory diseases and include diseases such as asbestosis. People with dust-related respiratory diseases may experience decreases in exercise capacity and quality of life. Therefore the research question for this review was: does exercise training improve exercise capacity and quality of life in people with dust-related respiratory diseases?

Why the review is important
There are very few treatments available for people with dust-related respiratory diseases. Exercise training in other chronic respiratory diseases helps to improve exercise capacity and quality of life. However, exercise training for people with dust-related respiratory diseases has not been examined well.

Studies we found
We included two studies with a total of 40 people (35 from one study and five from a second study). Of these people, 21 participated in exercise training and 19 did not participate in exercise training. All people were men and they were between 55 and 86 years old. Both exercise training programmes included cycling and walking and one programme also included strength training exercises. In both studies, training lasted for eight weeks with people attending two to three sessions per week.

Key results
Immediately following exercise training, people walked an average of 53.81 metres further in a six-minute walk test than those who did not complete exercise training. Six months following exercise training, people walked 52.68 metres further in a six-minute walk test than those who did not complete exercise training. These improvements in exercise capacity were similar for people with dust-related interstitial lung disease and people with asbestos related pleural disease. Quality of life also improved more in people who exercised compared to those who did not. No one reported experiencing any unwanted effects due to exercise training.

Quality of evidence
The quality of evidence was very low because there were only two studies and 40 people. Therefore, it is likely that these findings will change with more studies in the future. We need bigger studies that can confirm the findings of this Cochrane review.

Authors' conclusions: 

The evidence examining exercise training in people with non-malignant dust-related respiratory diseases is of very low quality. This is due to imprecision in the results from the small number of trials and the small number of participants, the indirectness of evidence due to a paucity of information on disease severity and the data from one study being from a subgroup of participants, and inconsistency from high heterogeneity in some results. Therefore, although the review findings indicate that an exercise training programme is effective in improving exercise capacity and health-related quality of life in the short-term and at six months follow-up, we remain unsure of these findings due to the very low quality evidence. Larger, high quality trials are needed to determine the strength of these findings.

Read the full abstract...
Background: 

Non-malignant dust-related respiratory diseases, such as asbestosis and silicosis, are similar to other chronic respiratory diseases and may be characterised by breathlessness, reduced exercise capacity and reduced health-related quality of life. Some non-malignant dust-related respiratory diseases are a global health issue and very few treatment options, including pharmacological, are available. Therefore, examining the role of exercise training is particularly important to determine whether exercise training is an effective treatment option in non-malignant dust-related respiratory diseases.

Objectives: 

To assess the effects of exercise training for people with non-malignant dust-related respiratory diseases compared with control, placebo or another non-exercise intervention on exercise capacity, health-related quality of life and levels of physical activity.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE/PubMed, EMBASE, CINAHL, PEDro and AMED (all searched from inception until February 2015), national and international clinical trial registries, reference lists of relevant papers and we contacted experts in the field for identification of suitable studies.

Selection criteria: 

We included only randomised controlled trials (RCTs) that compared exercise training of at least four weeks duration with no exercise training, placebo or another non-exercise intervention.

Data collection and analysis: 

We used standard methodological procedures expected by Cochrane. Two review authors independently assessed study eligibility and risk of bias, and extracted data. We employed the GRADE approach to assess the overall quality of evidence for each outcome and to interpret findings. We synthesized study results using a random-effects model based on the assessment of heterogeneity. We conducted subgroup analyses on participants with dust-related interstitial lung diseases (ILDs) and participants with asbestos related pleural disease (ARPD).

Main results: 

Two RCTs including a combined total of 40 participants (35 from one study and five from a second study) met the inclusion criteria. Twenty-one participants were randomised to the exercise training group and 19 participants were randomised to the control group. The included studies evaluated the effects of exercise training compared to a control group of no exercise training in people with dust-related ILDs and ARPD. The exercise training programme in both studies was in an outpatient setting for an eight-week period. The risk of bias was low in both studies. There were no reported adverse events of exercise training. Following exercise training, six-minute walk distance (6MWD) increased with a mean difference (MD) of 53.81 metres (m) (95% CI 34.36 to 73.26 m). Improvements were also seen in the domains of health-related quality of life: Chronic Respiratory Disease Questionnaire (CRQ) Dyspnoea domain (MD 2.58, 95% CI 0.72 to 4.44); CRQ Fatigue domain (MD 1.00, 95% CI 0.11 to 1.89); CRQ Emotional Function domain (MD 2.61, 95% CI 0.74 to 4.49); and CRQ Mastery domain (MD 1.51, 95% CI 0.29 to 2.72). Improvements in exercise capacity and health-related quality of life were also evident six months following the intervention period: 6MWD (MD 52.68 m, 95% CI 27.43 to 77.93 m); CRQ Dyspnoea domain (MD 3.03, 95% CI 1.41 to 4.66); CRQ Emotional Function domain (MD 5.57, 95% CI 2.34 to 8.81); and CRQ Mastery domain (MD 2.66, 95% CI 1.08 to 4.23). Exercise training did not result in improvements in the Modified Medical Research Council (MMRC) dyspnoea scale immediately following exercise training or six months following exercise training. The improvements following exercise training were similar in a subgroup of participants with dust-related ILDs and in a subgroup of participants with ARPD compared to the control group, with no statistically significant differences in treatment effects between the subgroups.

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