Rates of chronic suppurative otitis media (CSOM) among Aboriginal children living in remote areas in Australia are the highest in the world.1,2 A survey of 29 Aboriginal communities in the Northern Territory found that 40% of children had a tympanic membrane perforation (TMP) by 18 months of age.3 About 50%–80% of Aboriginal children with CSOM suffer from moderate to severe hearing loss.4,5 This occurs while language and speech are developing and may persist throughout primary school.

There is evidence suggesting that the recommended treatment for ear discharge (twice-daily cleaning and topical ciprofloxacin) can produce cure rates of 70%–90%.6–8 However, a study of Aboriginal children with CSOM in the NT found that less than 30% of children had resolution of ear discharge after 8 weeks of similar treatment.9 This study suggested that ongoing treatment for long periods was difficult for many Aboriginal families living in underresourced and stressful conditions. When children in high-risk communities do not receive appropriate medical treatment for ear disease, using swimming pools to limit levels of ear discharge and possibly reduce bacterial transmission becomes an attractive option.

Traditionally, children with perforated eardrums have been restricted from swimming because of fears of infection. However, it is hypothesised that swimming helps cleanse discharge from the middle ear, nasopharynx and hands and that this benefit may outweigh the risk of introducing infection. Several observational studies have examined the relationship between swimming and levels of skin and ear disease among Aboriginal children.10–14 In a cross-sectional survey, close proximity to a swimming area was associated with reductions of up to 40% in otitis media.10 Two systematic reviews have found that swimming without ear protection does not affect rates of recurrent ear discharge in children with tympanostomy tubes (grommets).15,16 Despite these findings, surveys indicate uncertainty among clinicians regarding water precautions for children with grommets.17–19

Our aim was to conduct a randomised controlled trial (RCT) to better understand the impact of swimming on children with CSOM, and to address a lack of data on ear discharge in older Aboriginal children (aged 5–12 years) with CSOM. We also aimed to obtain microbiological profiles of the nasopharynx and middle ear to help elucidate the cleansing hypothesis.

Parental consent was obtained for 89 eligible children: 41 children in the swimming group and 48 children in the non-swimming group (Box 1). At 4-week follow-up, final ear examinations were conducted on 82 children (36 swimmers and 46 non-swimmers).

At baseline, the study groups were similar in age, sex, perforation size, the presence and degree of ear discharge, and the prevalences of ear diagnoses (Box 2). Although there were no statistically significant differences in the baseline prevalence of bacteria in the nasopharynx or middle ear, swimmers had lower rates of H. influenzae in the nasopharynx and higher rates of S. aureus in both the nasopharynx and middle ear. Of the 89 children, 58 (26 swimmers and 32 non-swimmers) had ear discharge at baseline.

At 4-week follow-up, 56 children had ear discharge: 24 of 41 swimmers compared with 32 of 48 non-swimmers (RD, − 8%; 95% CI, − 28% to 12%). Excluding children lost to follow-up, 21 of 36 swimmers had ear discharge compared with 31 of 46 non-swimmers (RD, − 9%; 95% CI, − 30% to 12%).

Between baseline and 4-week follow-up, there was no statistically significant change in the prevalence of bacteria in the nasopharynx (Box 2). P. aeruginosa infection in the middle ear increased in swimmers, compared with no change in non-swimmers. Non-typeable H. influenzae isolated from ear discharge increased in both groups. Overall, the dominant organisms were S. pneumoniae and H. influenzae in the nasopharynx, and H. influenzae, S. aureus and P. aeruginosa in the middle ear.

Per-protocol analysis of swimmers attending > 75% of swimming classes and non-swimmers adhering to swimming restrictions > 75% of the time indicated that 16 of 24 swimmers had ear discharge at 4-week follow-up, compared with 29 of 44 non-swimmers (RD, 1%; 95% CI, − 23% to 23%).

Rates of discharge were significantly lower in children who were prescribed ciprofloxacin and in children with smaller perforations (Box 3).

Of the 89 children, 65 had no change from their original diagnosis (by child’s worst ear) at 4-week follow-up. Ear discharge failed to resolve in 31 of the 35 participants with moderate to profuse ear discharge at baseline (Box 3). Seven of the 89 children had a perforation that healed (Box 4).

We found that regular swimming in a chlorinated pool for 4 weeks did not aid resolution of ear discharge in Aboriginal children with CSOM. At the end of the trial, rates of ear discharge were similar between swimmers and non-swimmers. Our microbiological data also suggest that swimming is unlikely to be effective in removing discharge from the middle ear and nasopharynx, with rates and densities of organisms generally comparable between swimmers and non-swimmers, with little change during the study. Among swimmers, there was an increase in P. aeruginosa middle ear infection, but this was not correlated with new episodes of ear discharge.

Our study is the first RCT to examine the effects of swimming on Aboriginal children with CSOM and also addresses the need for more RCTs examining the impact of swimming on children with grommets. Further, the microbiological data enabled an assessment of the effect of regular swimming on infection in the nasopharynx and middle ear. Other strengths include the blinding of examiners, prespecified subgroup analysis and a follow-up rate of more than 90%.

Our study also has some limitations. We planned to randomly assign 100 children and anticipated that 90% of participants would have ear discharge at follow-up, but we had only 89 participants and 63% with discharge at follow-up, meaning the study was underpowered. Some difficulties were encountered in recruiting children who did not attend school in one community. The possibility of contamination among non-swimmers was also a concern. Parents and school and pool staff assisted in ensuring that non-swimmers did not swim at the pool or at any other water sites, and alternative activities were provided for non-swimmers after school, as this was a popular swimming time. Attendance at swimming and activity classes were monitored, and two portable media players were offered as incentives to children with the highest attendance.

The lack of objective measures for the degree of discharge, perforation size and bacterial density may have contributed to measurement error. It is unlikely that these limitations would prevent a large clinical effect being identified. However, our small sample size means that modest benefits or harms associated with daily swimming may still be possible.

Our results are not consistent with research from two remote communities in Western Australia, which found that rates of TMPs among Aboriginal children halved from about 30% to 15% after swimming pools were installed.11 The potential to improve on our results with longer exposure to swimming is possible. However, the WA study did not follow individual children, and after 5 years the reductions were sustained in only one community.14 Further, the likelihood of significant clinical improvements over a longer period is not supported by our microbiological data. A recent South Australian study also found that the installation of swimming pools in six communities did not affect rates of TMPs among children.12

While swimming may remove some ear and nasal discharge, there is evidence to suggest that cleansing practices alone will not cure CSOM. A Cochrane review of studies conducted in developing countries found that wet irrigation or dry mopping was no more effective than no treatment in resolving ear discharge in children with CSOM (odds ratio, 0.63; 95% CI, 0.36–1.12).21 The review recommended that aural cleansing should be conducted in conjunction with topical antibiotic therapy.21 Future studies could look at the effectiveness of swimming in combination with the application of topical antibiotic therapy.

Over the 4 weeks of our intervention, rates of H. influenzae middle ear infection substantially increased in both swimmers (from 35% to 70%) and non-swimmers (from 50% to 65%). Previous topical antibiotic trials of Aboriginal children (aged 1–16 years) have reported lower baseline rates of H. influenzae in the middle ear, ranging from 5% to 25%.6,9 In contrast, a vaccination trial of Aboriginal infants aged < 24 months found H. influenzae in 85% of new perforations.22 The high levels of H. influenzae ear and nasopharyngeal infection may mean that there is a role for the use of oral antibiotics in combination with topical antibiotics to treat Aboriginal children with CSOM. There may also be benefits from vaccines against H. influenzae in Aboriginal children at high risk of progressing to CSOM.

Simultaneous hand contamination and nasal carriage of S. pneumoniae and H. influenzae is a reliable indicator of TMP in Aboriginal children under 4 years of age.23 Future research could examine rates of hand contamination in relation to swimming, particularly targeting younger children (aged 2–5 years), who are most likely to transmit otitis media bacteria to infants.

In conclusion, it seems unlikely that regular swimming in pools will resolve ear discharge and heal TMPs in the short term. We also found no clear indication that swimming reduces rates of respiratory and opportunistic bacteria in the nasopharynx or middle ear. However, we did not find swimming to be associated with an increased risk of ear discharge. We would not support the practice of restricting children with a TMP from swimming unless it was documented that ear discharge developed directly after swimming (for that particular child). More RCTs are needed to assess more modest (or longer-term) effects of swimming on middle ear disease in Aboriginal children. The combination of swimming and ciprofloxacin treatment may also produce better clinical outcomes and should be investigated.

1 Flowchart of participants through the trial

TMP = tympanic membrane perforation.