Children with Permanent Hearing Loss and Associated Disabilities: Revisiting Current Epidemiological Data and Causes of Deafness

Article excerpt

This article reviews current epidemiological studies estimating the prevalence and incidence of permanent hearing loss in children. In particular, it addresses trends in ages of onset of hearing loss and causes. Studies estimating the number of children with hearing loss and additional special needs in various countries are presented, as well as some of the well-known causes of hearing loss which have co-occurring associated disabilities. The case of linguistically diverse children is presented as a new group of children with hearing loss who may function with multiple disabilities.

Introduction

Epidemiological studies estimating the prevalence1 of permanent hearing loss in children at various ages are of paramount importance to set priorities for prevention and treatment (Parving, 1999). Given the high prevalence of this condition in babies, infants, and young children (Northern & Downs, 2002), and its devastating consequences resulting in life-long disability if left untreated (Northern & Hayes, 1994), permanent hearing loss in children must be acted upon diligently and as early as possible in life (Yoshinaga-Itano, Sedey, Coulter, & Mehl, 1998). Within this context, the goal of the present analysis was to review current knowledge of epidemiological data and present an understanding of how the causes of deafness may be associated with additional special needs.

Current Status on Epidemiology of Permanent Hearing Loss in Babies, Infants, and Young Children

The global prevalence of permanent (or sensorineural) hearing loss in the newborn population is currently estimated by Mencher (2000) at 1.368 in every 1,000 live births in the world. This is comparable to the 1 to 2 incidents of hearing loss per every 1,000 births as reported by Downs and Sterritt in 1964. In fact, there is a wide variety in current estimates of hearing losses worldwide, with ratios ranging between the low of 0.43 per 1,000 (Germany) and the high of 4/1000 (Sierra Leon and Thailand). The current estimate for the United States has declined to 0.71/1000 (Mencher, 2000), which is also the rate for Belgium. Data from the 1980s places Canada at the lower end with a ratio of 1.046/1000. This is close to the prevalence of 1.06/1000 for hearing loss ≥40 dB in the United Kingdom (Fortnum, Summerfield, Marshall, Davis, & Bamford, 2001). On average, European countries are showing lower prevalence estimates: France at 0.54/1,000 live births (Parving, 1999; Baille et al., 1996); Italy at 0.9/1000 in the early 1980s (Mencher, 2000) rising to 2.3/1000 with the inclusion of older children (Parving, 1999); and, Germany with a reported ratio of 0.43/1000 (Streppell, et al., 1998; Streppell, Richling, Walger, von Wedel, & Eckel, 2000). Even a small country like Cyprus is exemplary in this particular respect, with reported estimates of 0.4/1000 to 0.6/1,000 in the mid-1990s (Hadjikadou & Bamford, 2000). One notable exception to this trend is the former Soviet Republic, Estonia, which declared a ratio of 1.52/1000 between 1985 and 1990 (Uus & Davis, 2000).

In comparison, there are consistent indications of the high prevalence of newborn hearing loss in Asian children (Fortnum & Davis, 1997; Naeem & Newton, 1996), and in Pakistani groups (Morton, Sharma, Nicholson, Broderick, & Poyser, 2002) as derived from cohorts living in the United Kingdom. The prevalence of hearing loss in Asian children may be two to three times that of the non-Asian population. The same would be true of Hispanic groups living in the United States (Lee, Gomez-Marin, & Lee, 1996). Sociodemographic and educational variables (poverty and lower educational attainment by parents) may be contributing factors (Lee, Gomez-Marin, & Lee, 1997). Similarly, limited access to quality medical assistance during pregnancy and the early postnatal years may be an additional factor.

While there is a reported decline in hearing loss in newborns and young children in more developed countries, there appears to be an almost twofold increase in the numbers of children with acquired hearing loss between the ages of 3 and 9 years. …