Background

Swimming is often recommended as a form of physical activity for children with asthma. It is proposed to be superior to other forms of exercise for children with asthma due to the humidified and warm air, low pollen count exposure and hydrostatic pressure on the thoracic wall.1 However, some studies have raised concerns in relation to the potential proasthmatic effect of chlorinated pools.2 ,3

Aim

The aim of the systematic review was to determine the effectiveness and safety of swimming training as an intervention for asthma in children and adolescents.

Searches and inclusion criteria

An electronic search was performed using the Cochrane Airways Group Specialised Register of trials, as well as the CENTRAL, PubMed, CINAHL and EMBASE databases in July 2012. A number of clinical trial registries were also searched for ongoing studies and reference lists of all included studies were screened.

To be eligible for inclusion in the review, studies had to be randomised controlled trials (RCTs) or quasi-RCTs of children or adolescents aged less than 18 years, with a diagnosis of asthma, in which the intervention was swimming training.

Interventions

Swimming training was defined as a formal swimming programme of at least one session per week for a minimum of 4 weeks, lasting at least 20 min per session. The control interventions could be either usual care alone, non-physical activity or physical activity other than swimming.

Main outcome measures

The primary outcome measures were: quality of life measured by disease-specific or generic questionnaires; asthma control measured by questionnaires or symptom diaries; exacerbations requiring attendance at hospital; and systematic steroid use. Secondary outcomes included bronchodilator use, inhaled steroid use, lung function, exercise capacity, bronchial hyper-responsiveness, time off from school and utilisation of healthcare services.

Statistical methods

For continuous outcomes using the same scale, mean difference and 95% CIs were calculated using change from baseline where available. Where different scales were used, standardised mean differences (SMD) and 95% CIs were calculated. For dichotomous outcomes, results were expressed as Peto ORs with 95% CI.

Where data were available, studies were combined with meta-analysis. In the case of high levels of heterogeneity (assessed using the I² statistic), the causes were explored using sensitivity analyses, or a random-effects meta-analysis was performed or no meta-analysis was conducted.

Prespecified subgroup analyses were conducted when a sufficient number of studies were available. Sensitivity analyses were conducted by excluding studies with a high risk of bias.

Limitations

Only four studies provided details on the method of randomisation and were considered to be at low risk of bias. Two of these studies reported concealed allocation to groups. Blinding was not possible in any study due to the nature of the intervention. Three studies had a high withdrawal rate and were considered at high risk of bias due to incomplete outcome reporting. Of the 262 randomised participants in the eight studies, 42 withdrew early.

Clinical implications

Swimming training is well tolerated in children and adolescents with stable asthma. There is moderate strength evidence that it increases lung function and high strength evidence that it increases cardiopulmonary fitness. There was no evidence that swimming causes adverse effects on asthma control. However, whether swimming is better than other forms of physical activity cannot be determined from this review.