Minimal Hearing Loss in Children: The Facts and the Fiction

Address correspondence to: Anne Marie Tharpe, Ph.D., Professor, Vanderbilt Bill Wilkerson Center, 1215 21st Ave. So., #8310, Medical Center East, So. Tower, Nashville, TN. 37232-8242, [email protected]. Since that time, others have adopted these definitions in an effort to enable meaningful comparisons of data across studies (Centers for Disease Control and Prevention 2005). Our attempts to evaluate current data obtained across studies are compromised when we are not using uniform definitions. For example, prevalence rates of minimal or mild bilateral hearing loss and unilateral hearing loss are uncertain because of the differences in defining the audiometric thresholds of these groups. Furthermore, because we do not currently target minimal and mild degrees of hearing loss with our newborn hearing screening programs, we can only estimate prevalence of such losses in the newborn period. Johnson and colleagues (2005) offered a conservative estimate of 0.55/1000 newborns with mild permanent bilateral (25–40 dB at 1.0, 2.0, or 4.0 kHz) and unilateral hearing loss. The number of babies with unilateral hearing loss in the neonatal period has been estimated at 0.7–1/1000 (Prieve et al. 2000; Davis, DeVoe and Robertson 2005) as compared to 3/100 by school age (Bess et al. 1998). Bess and colleagues also estimated 2.4/100 school-age children had minimal bilateral hearing loss. The difference between estimated prevalence rates in the newborn period and at school age can be the result of several different factors including: • misses by the early hearing detection and intervention systems (EHDI); • low follow-up rates by newborn screening programs resulting in low estimates in the newborn period; • progressive or late-onset hearing loss; and/or • differing definitions of “hearing loss”. This chapter will review what we know about the impact of minimal degrees of hearing loss on children. Perhaps more importantly, what we do not know about the effects of these degrees of hearing loss will also be discussed.