In contrast to previous studies about children with UHL, we enrolled a large number of elementary school-aged children, carefully described their hearing, cognitive, and socioeconomic status, and included sibling controls. The results showed that UHL is associated with a significant negative effect on scores on standardized speech-language tests. Obtaining cases and controls within families controlled for a host of family, genetic, socioeconomic and environmental factors that could affect language development. Although speech-language scores do not translate directly into school performance, the secondary outcomes of speech therapy and IEPs suggest that the children with UHL had significant problems in school. The multivariable analysis suggested that use of amplification might be associated with a small increase in LC scores. We do not think selection bias influences these results because the participants with UHL were identified through hearing screening programs or diagnostic audiograms, not through special services programs at schools.
The etiology of UHL in children may encompass a different spectrum than BHL. Genetic mutations, such as connexin 26 mutations, rarely cause UHL, and syndromic hearing loss usually involves both ears.25
The most common known etiologies in UHL are temporal bone anomalies such as enlarged vestibular aqueduct, cochlear dysplasias, and cochlear nerve aplasia.26-28
Familial or hereditary UHL is rare and not well characterized.29-31
Head trauma is a relatively common etiology of acquired UHL, but the frequencies of intrauterine infections, meningitis, otologic surgery, and ototoxic medications in UHL have not been well-tallied.32
Children with microtia or auricular atresia may have syndromic hearing loss (e.g., Goldenhar syndrome), but usually have conductive or mixed hearing loss that are well-treated with Baha®.33-35
Because neonatal risk factors for hearing loss have been identified in children with congenital BHL, it is not known if the same risk factors are important for children with UHL. Research is necessary to discover which risk factors and etiologies are associated with UHL.
No study of UHL has investigated whether severity of hearing loss affects speech or language outcomes. However, studies in children and adults with asymmetric BHL show that sound localization and speech discrimination are more difficult and outcomes are poorer than with symmetric BHL.36-39
We speculate that when the difference in hearing between ears exceeds a threshold level, a person with UHL may experience difficulty with sound localization or speech discrimination in noise similar that experienced by those with asymmetric BHL. However, further research is necessary to determine whether a threshold effect might exist.
Unlike children with BHL, who are routinely fitted with hearing aids and receive accommodations for disability, children with UHL may not be considered to have a “significant hearing loss” because their hearing loss is not bilateral (e.g., Delaware) or not sufficient to interfere with speech or language development (e.g., Arkansas, Kentucky, Utah).40
Each state has the right to define who is eligible for Part B and Part C of the Individual with Disabilities Education Improvement Act of 2004 (IDEA), and UHL is often not included.41
Therefore, children with UHL are not automatically eligible for services in First Steps or Birth to Three programs (Part C of IDEA), pre-school or school IEPs (Part B of IDEA), or Section 504c of the Rehabilitation Act of 1973 accommodations for disability.42
Recommended interventions for children with UHL usually include preferential seating in class and an FM system that amplifies the teacher’s voice relative to the background noise. Unless the child has another school-related issue (such as speech or behavior), or demonstrates significant developmental or educational delay, parents must often strongly advocate for their children with UHL to obtain FM systems in the classroom. Additionally, parents may be actively discouraged by school teachers and administrators from seeking Section 504c accommodations. Only 3 children with UHL in this study had Section 504c accommodations. Independent private or parochial schools may not have the resources or the mandate to provide these accommodations. The present results suggest that children with UHL should be eligible for the same accommodations as children with BHL.
Health disparities affected this study cohort significantly. Poverty was associated with decreases in speech-language scores similar in magnitude to UHL. Compared to those in the >200% FPL bracket, the OE and OC scores for children from families at 100-200% of FPL were lower by 4 points, and lower by 7-8 points in children from families <100% of FPL. Thus, a child with UHL who comes from a family with an income <100% FPL would be expected to have an OE score 11 points and OC score 14 points below a child with NH and family income >200% FPL. These large differences in oral language skills based on socioeconomic status are consistent with education and health disparities noted by others,43
and have policy implications for health care and education. Although gaps in standardized achievement scores have not been measured directly in this cohort, speech and language development contributes to reading and literacy.44-46
Interventions that reduce the negative impact of UHL on children should address both the functional problem of hearing with only one ear, and the problems poverty encompasses in affecting childhood language development.
Future research to determine when the onset of speech-language delays occurs, the mechanisms whereby UHL affects speech-language development, whether any interventions can mitigate the effects of UHL, and whether speech-language delays affect future educational performance and job acquisition are all necessary to allow children the opportunity to attain their potential.