Occupational exposure to noise, vibrations and chemicals during pregnancy and hearing disability in children

Children with hearing disabilities struggle more during their school time, perform worse than their peers, and finish school without passing grades to a larger extent.

Even though noise is one of the most important factors for adult hearing disability, knowledge is lacking regarding the effects of noise on fetal development.

A few studies have indicated that high exposure to noise during pregnancy may increase the risk of hearing disability in the child.

However, it is still unknown: i) whether there are any dose-response effects, ii) at what levels noise starts to get harmful, and iii) if there are specific periods during which the developing ear is more sensitive to noise.

Despite the close relationship between noise and vibration, it is unknown whether exposure also to vibrations during pregnancy could increase the risk of hearing disability in the child.

Finally, studies on animals and adults have shown that certain chemicals may also increase the risk of hearing disability, but it is not known whether such chemicals could affect the developing ear as well.The planned study offers a unique opportunity to answer these questions by merging two cohorts created though combining data from multiple, national, Swedish registers.

The cohorts include all children born in Sweden between 1986-2014 (n≈3 million births of which 1.8 million included working mothers) and contain information on the mother’s occupation during pregnancy and multiple lifestyle factors. In addition to the cohorts, advanced job-exposure matrices have been developed and are now being updated.

In these matrices, the exposure to a certain factor has been estimated for each occupation using previously reported measurement data.

By matching on mother’s occupation, exposure during pregnancy can be estimated for each of the potentially harmful factors.

For the planed study, data on children’s hearing diagnosis will be ordered from the patient register through the National Board of Health and Welfare.