Research offers insights into the development of children’s sounds

While the effects of deafness in early childhood have been proven to lead to lasting changes in how sounds are processed in the brain, new research from Cambridge University has shown that even mild to moderate levels of hearing loss in young children can be just as detrimental. 

The findings will be of interest to all those working with young children in the early childhood education and care (ECEC) sector, but especially so for those working with First Nations children. 

Ear disease and associated hearing loss, according to World Health Organisation statistics, is “highly prevalent” among Aboriginal and Torres Strait Islander children. Otitis media is the key condition contributing to hearing loss among Indigenous children, and is typically caused by bacterial and viral pathogens that also cause common childhood illnesses. 

The clinical presentation of otitis media infections differs for Indigenous and non-Indigenous children. Otitis media is characterised in Indigenous children by a younger age at first episode, higher frequency of infection, greater severity and greater persistence than in non-Indigenous children (Jervis-Bardy et al. 2017). Repeated ear infections, which are often undiagnosed and untreated, are substantially and significantly associated with hearing problems at a later stage (Yiengprugsawan et al. 2013). Between the ages of two and 20, an Indigenous child or young person is likely to experience hearing loss from middle ear infections for at least 32 months, compared with three months for non-Indigenous children/young people (Kong & Coates 2009). 

Cambridge researchers say their findings may have implications for how babies are screened for hearing loss and how mild-to-moderate hearing loss in children is managed by healthcare providers.

To further explain the significance of the findings, researchers outlined the structure and function of the auditory system, which processes sounds in the brain and develops throughout childhood in response to exposure to sounds. 

In profoundly deaf children, the auditory system undergoes a functional reorganisation, repurposing itself to respond more to visual stimuli, for example. However, until now relatively little was known about the effects of mild-to-moderate hearing loss during childhood.

The research team was led by Dr Lorna Halliday, who used an electroencephalogram (EEG) technique to measure the brain responses of 46 children who had been diagnosed with permanent mild-to-moderate hearing loss while they were listening to sounds.

Dividing the children into two groups – younger children (8-12 years) and older children (12-16 years) – the team found that the younger children with hearing loss showed relatively typical brain responses – in other words, similar to those of children with normal hearing. However, the brain responses of older children with hearing loss were smaller than those of their normally hearing peers.

To confirm these findings, the researchers re-tested a subset of the group of younger children from the original study, six years later. In the follow-up study, the researchers confirmed that as the children with hearing loss grew older, their brain responses changed. 

Responses that were present when the children were younger had either disappeared or grown smaller by the time the children were older. There was no evidence that the children’s hearing loss had worsened over this time, suggesting instead that a functional reorganisation was occurring.

Supporting researcher and lead author Dr Axelle Calcus said that while current screening programmes for newborn babies are good at picking up moderate-to-profound levels of hearing loss, they are not well positioned to detect mild hearing loss. 

“This means that children with mild hearing impairment might not be detected until later in childhood, if at all,” Dr Halliday said.

“Children with hearing problems tend to do less well than their peers in terms of language development and academic performance. Detecting even mild degrees of hearing impairment earlier could lead to earlier intervention that would limit these brain changes, and improve children’s chances of developing normal language,” she added.

The research was funded by the Economic and Social Research Council and the European Union Horizon 2020 Programme. The research was carried out at University College London (UCL) and may be accessed here.