As an audiologist proceeds through the steps in evaluating a child's hearing abilities-identifying the existence of a hearing loss; determining its degree and impact on communication ability; and planning and providing (re)habilitative treatment, including fitting amplification devices, conducting auditory training, and counseling and supporting the child and her family-does the audiologist consider if any of these steps need to be modified based on differences among culturally and linguistically diverse (CLD) populations?
Consider the effects of hearing loss on speech perception. Children with hearing loss who speak Mandarin Chinese appear able to develop spoken language without the use of amplification. Tone perception in Mandarin Chinese may explain this in part. The ability to recognize Mandarin tones is largely preserved in native Mandarin speakers with mild and moderate sensorineural hearing loss (Liu, Hsu, & Horng, 2000). In Spanish, word understanding essentially depends on lower frequency consonants and vowels. Children with high frequency hearing loss, raised in monolingual Spanish homes, can often compensate for the hearing loss. These children typically have normal speech and language development and good articulation and intelligibility in their native language (Abreu, 1995).
Scores obtained while testing speech in noise can be affected by the first language of the listener. Children learning English as a second language have significantly poorer scores when listening to speech in noise. The differences between them and monolingual English-speaking children increase as the signal-to-noise ratio (SNR) becomes less favorable (Crandell & Smaldino, 1996).
Demographics of Hearing Loss
According to the United States Department of Education, the number of students with disabilities served under the Individuals with Disabilities Education Act (IDEA) continues to grow. The racial/ethnic breakdown of children between the ages of 6 and 21 years served under IDEA, Part B for 1998-99 showed some differences as compared to the general population. For example, African American children represented 14.8% of the general population and 16.8% of children with hearing impairment. Hispanic children accounted for 14.2% of the general population and 16.3% of children with hearing impairment. White children represented 66.3% of the general population and 63.0% of students classified as hearing impaired.
Children from CLD populations thus comprise more of the population with hearing impairment. Audiologists need to be aware of potential influences due to racial/ethnic differences that can be found during a routine audiological evaluation. In the Asian American population, for example, it is common to find shallow tympanograms, which do not indicate a compromised middle ear system, and southern Chinese have been found to have lower peaks, wider tympanometric width, and more positive peak pressure than westerners (Wan & Wong, 2002).
Etiology of Hearing Loss
For more than 30 years, the Gallaudet Research Institute has conducted its Annual Survey of Deaf and Hard-of-Hearing Children and Youth. The survey, which is the largest ongoing database of information on deaf and hard-of-hearing children in the United States, collects different kinds of data including etiology of hearing loss. For more than 15 years, heredity, meningitis, and prematurity have been the three primary causes of hearing loss across all racial and ethnic groups.
Recent advances in genetic research have increased the frequency with which genetic syndromes are reported to the Annual Survey. In addition, the number of instances of cytomegalovirus (CMV) reported to the Annual Survey has climbed steadily since the mid-1980s (Schildroth, 1994). CMV is one of the leading causes of nongenetic severe-to-profound hearing impairment in infants and children.
Although CMV is found in all geographic locations and socioeconomic groups, the Centers for Disease Control and Prevention (1999) has reported that it is more prevalent in areas of lower socioeconomic conditions. African American, Hispanic, and American Indian children are more likely to live in poverty and have less access to health care. Over the years, African American and Hispanic children have been disproportionately represented in the categories of prematurity and meningitis, while African American children have also been disproportionately represented among cases of CMV.
Low Birth Weight
Congenital bilateral sensorineural hearing loss affects approximately 10 children per 10,000 live births annually in the U.S. It is more prevalent among low birth weight (LBW; <2500 g) children, particularly very low birth weight (VLBW; <1500 g) children. The high rate of hearing loss among LBW children has been linked to several factors that may result in brain damage and hearing impairment. These factors include short gestational age, administration of ototoxic drugs, ambient incubator noise, perinatal complications (e.g., hypoxia), and neonatal and postneonatal complications associated with lower birth weight.
The factors associated with low birth weight in neonates include age of the mother, delayed or no prenatal care, mother's socioeconomic background, and tobacco use during pregnancy. Studies have reported that the percentage of African American mothers who give birth to neonates weighing less than 1,500 g is higher than any other racial/ethnic group (MacDorman & Atkinson, 1999).
Based on the association between LBW and higher prevalence of hearing loss, Van Naarden and Decoufle (1999) conducted a study to determine the prevalence of congenital bilateral sensorineural hearing loss (SNHL) in relation to lower birth weight among children born in the 1980s and living in the Atlanta area. Of the 169 children ultimately included in the study, more than half were African American. The overall prevalence rate of presumed congenital bilateral sensorineural hearing impairment was 5.3 cases per 10,000 three-year survivors. Lower birth weight was directly related to a higher prevalence of bilateral SNHL. The prevalence rate was 4.1 per 10,000 children weighing >/= 4000 g, while it was 51.0 per 10,000 among those weighing <1500 g.
This study revealed that African American children weighing <2500 g had much higher rates of hearing loss than their white peers. Interestingly, the prevalence rates of hearing loss for normal birth weight (NBW) and borderline normal birth weight African American males were consistently higher than those for white children of both sexes and African American females. Etiologic data were limited; however, of the 12 NBW African American males with a known etiology for the hearing loss, seven were the result of meningitis.
As noted previously, severe-to-profound congenital hearing loss affects 1 in 1,000 newborns. In half of these infants, the hearing loss is genetic due to either syndromic or nonsyndromic causes. Nonsyndromic genetic hearing losses predominate, comprising 70% of congenital hereditary hearing losses. Additionally, approximately 77% of congenital hearing losses are recessively inherited, 22% are dominantly inherited, and the rest are X-linked or mitochondrial (Gorlin, Toriello, & Cohen, 1995). Thus, for half of all infants with severe-to-profound congenital hearing loss, their loss is most likely a nonsyndromic genetic hearing loss recessively inherited.
In 1997 a deafness-causing gene GJB2 was identified. GJB2 encodes the protein connexin 26 (Cx26), an essential component of the potassium (K) pathway, a flow loop facilitating K circulation needed to maintain the high K concentration in scala media.
Cx26 mutations have been found in approximately one-half of persons with severe-to-profound congenital nonsyndromic sensorineural hearing loss. Although more than 22 different deafness-causing mutations of Cx26 have been described, in many populations it appears that a single mutation predominates (McGuirt & Smith, 1999). However, different single mutations can predominate in different populations.
One such mutation is designated as 35delG. The carrier rate for the 35delG mutation in the midwestern U.S. is approximately 2.5% and in this population about two-thirds of persons with Cx26-related deafness are 35delG homozygotes (they carry two copies of the mutation). However, in the Ashkenazi Jewish population another Cx26 mutation predominates, the 167delT mutation. It has a carrier frequency of 4.03% compared to a carrier rate of 0.73% for the 35delG mutation (Green et al., 1999). Additionally, in the Japanese population, the 35delG mutation is not a common cause of Cx26-related deafness (Usami et al. 1999).
If a white child has a prelingual hearing loss of unknown etiology, genetic testing for Cx26 is highly recommended for two major reasons. The first is that Cx26 accounts for 50% of severe-to-profound prelingual nonsyndromic hearing losses and, secondly, a single mutation is present in more than 97.5% of white persons with Cx26-related deafness (Green et al., 1999). Specific recommendations for genetic testing may differ based on the child's racial/ethnic background.
Nonsyndromic hearing loss can also be caused by mitochondrial mutations. Mitochondria are small organelles found in cells. They have their own DNA. One type of mitochondrial mutation makes individuals susceptible to hearing impairment after treatment with aminoglycosides (antibiotics) at concentrations that do not normally affect hearing. Yet, this one mutation can have different effects across different populations.
In families from Zaire and Spain, researchers have found this mitochondrial mutation at higher than expected rates and in family members who went deaf with and without administration of aminoglycosides. In Shanghai, the same mutation accounts for 30% of aminoglycoside-induced hearing loss, while in the U.S. it accounts for only about 15% of aminoglycoside-induced HL (Fischel-Ghodsian, 1998).
Another mitochondrial mutation has been found in Scotland; however, with a very low penetrance for hearing loss. Yet in New Zealand and Japan, the same mutation has a high penetrance for hearing loss. Apparently, the mutation by itself is not sufficient to cause a hearing loss; additional genetic or environmental factors are needed. In Scotland these factors appear to be rare, while in New Zealand and Japan they appear to be common (Fischel-Ghodsian, 1998).
Sickle Cell Disease
Though numerous studies have been conducted over the years examining auditory function in persons with sickle cell disease (SCD), fewer of them have included children as subjects. Group studies examining auditory function in children with SCD have found some evidence of auditory dysfunction. The prevalence of SNHL in pediatric populations with SCD generally is lower than that found among adult populations with SCD. Both groups exhibit various forms of central auditory dysfunction. Longitudinal studies of auditory function are needed along with differentiation among subjects with varying degrees of severity (mild, moderate, and severe) and various forms of SCD (sickle cell anemia, sickle cell hemoglobin C disease, and sickle cell thalassemia) (Scott, 2004).
Otitis Media & Tympanostomy Tubes
Otitis media is the most frequent diagnosis for children's visits to physicians' offices in the U.S. By three years of age approximately 75% of all children have had at least one episode of acute otitis media, and more than 33% have had three or more episodes.
One common method of treating otitis media is insertion of tympanostomy tubes, commonly referred to as PE tubes. The effectiveness of tubes for ventilation of the middle ear space, restoration of hearing, and prevention of new episodes of otitis media in severely affected children has long been established. The new guidelines on care for children with otitis media with effusion (OME) apply to children aged 2 months to 12 years with or without developmental disabilities. Expanding the age range for which the guidelines apply is important because children with developmental disabilities are often at risk for OME (Guide to Otitis Media with Effusion, 2004).
In the U.S., insertion of tympanostomy tubes has become the most common surgical procedure (excluding circumcision) for children under the age of 15 years (Pokras, Kozak, & McCarthy, 1997). Studies examining tympanostomy tube insertion have found that after controlling for the number of ear infections, the factors associated with a greater likelihood of PE tube insertion are gaps in health insurance coverage among children who attend a day care center, who are white, whose birth weight was <1500 g, and who live in the midwest or the south (Kogan et al., 2000).
It is a major concern that children without continuous health insurance coverage and/or who are nonwhite are less likely to receive PE tubes. This finding is consistent with others indicating that lack of health insurance leads to less access to care. Since otitis media may have long-term cognitive and language developmental effects, children without continuous health insurance coverage may remain at a disadvantage. A disproportionate number of African American and Hispanic children may be included in those numbers of children without continuous health insurance coverage.
CLD children who are deaf are dealing with at least three cultures-the culture of their ethnic/racial group, the culture of the Deaf community, and the mainstream culture. The most rapidly growing group of CLD deaf students is Hispanic.
How linguistically diverse are the homes of these children? It is generally accepted that children who are deaf and who have parents who are deaf will use American Sign Language (ASL), but what about children who are deaf who are exposed to languages other than English and ASL? Questions of language dominance and language proficiency in English and any other languages spoken or signed must be answered. The dominant language should be used for assessing the child, although it is important to know the child's proficiency in all languages spoken or signed.
What is the decision-making process for Hispanic families living in the United States who have a child with hearing loss? Families have shared their experiences in searching for appropriate interventions and making choices regarding communication and education. Spanish-speaking families' decisions are complicated by language and cultural barriers and by limited access to information and resources. The communication method chosen tends to be the one recommended by professionals, usually a combination of spoken English and sign language. Yet the parents frequently express the hope that their children would learn spoken Spanish as well (Steinberg et al., 2003).
Historically, educational services provided to deaf persons from CLD populations have been inferior to those provided to deaf persons from the majority population. The exit rates reported on the 1993-94 Annual Survey of Deaf and Hard of Hearing Children and Youth showed more racial/ethnic minorities graduated with certificates as compared to diplomas than white students (Schildroth & Hotto, 1995). Hispanic students had a higher dropout rate than African Americans or Asian/Pacific Islanders.
Data on deaf and hard-of-hearing students exiting high school reveal some intriguing differences. Students exiting at 17 years of age are primarily white and the majority have only one disability. On the other hand, students exiting at 20-21 years of age are primarily nonwhite, and the majority have one or more additional disabilities (Allen, 1994).
Early identification of hearing loss is essential for development of speech/language skills across all racial/ethnic groups. Yoshinaga-Itano (2000) reported that children identified as deaf or hard of hearing before 6 months of age and who received immediate and appropriate intervention maintained age-appropriate language skills from 12 months through 3 years, regardless of hearing loss, race/ethnicity, socioeconomic status, and mode of communication.
Given this brief review, it is clear that research studies are needed on the prevalence of hearing impairment across racial/ethnic populations (e.g., studies examining the relationship between birth weight and prevalence of hearing impairment); genetic hearing loss across racial/ethnic populations; access to health care, which in turn may affect the development or resolution of a hearing disorder; and the effects of language and culture on how and what kind of intervention services should be provided.