To the Editor:
Hearing impairment has been reported as occurring in 1 to 2 per 1000 neonates.1,2 However, hearing loss is a highly heterogeneous condition, with varying severity (mild, moderate, severe, and profound) and type (conductive, sensorineural, and mixed). Hearing loss can be unilateral or bilateral, stable or progressive, and temporary or permanent.
Hearing “loss” or impairment typically refers to a hearing limit of 40 dB for the better ear.1 With wider inclusion criteria for hearing impairment (a limit of 25 dB in the worse ear), the prevalence of hearing impairment in infants has been reported as 2 to 3 per 1,000.2 Profound hearing loss defined as a bilateral sensorineural hearing limit of ≥ 70 dB has been reported in 4 to 10 per 10,000.3 Thus, population levels of hearing loss are highly dependent on definition.
We present a detailed description of hearing impairment in Polish children up to 1 year of age. This population is relatively homogenous with respect to ethnic background, socioeconomic conditions, and health status. Data were obtained through the Polish Universal Neonatal Hearing Screening Program, organized and run by the charity foundation Great Orchestra of Christmas Charity (www.wosp.org.pl/eng). The program started in 2002, and since January 2003 has tested all newborns in Poland,4 >3.5 million babies. On the basis of data from the Polish Central Statistical Office, we estimate that 96% of the newborn population in Poland are screened in this program.
Our results are based on infants registered in the program database between 2003 and 2011 (3,322,349 babies). Of these screened children, 9% (n = 292,375) were referred for further hearing evaluation. Among these, 9872 children (2.97 per 1000 infants) were diagnosed as having a hearing problem (defined as any hearing impairment with a threshold >20 dB). However, this evaluation did not originally specify diagnosis type or severity. More thorough evaluation was initiated after the start of the program and covered 5443 of the 9872 children. Assuming that the children who received thorough screening are representative of all children with hearing impairments, we have estimated the following population prevalence.
Permanent (sensorineural) bilateral hearing impairment was found in 1.38 per 1000 children (Table). Of these, 40% had severe-to-profound bilateral hearing loss (the most devastating) (0.55 per 1,000). Of the two other types of bilateral hearing impairment, conductive loss was found in 0.47 per 1,000 and mixed hearing loss in 0.24 per 1,000, with a total of 2.09 per 1,000 having bilateral hearing loss. Including those with unilateral hearing loss, serious hearing loss was present among 3.0 per 1000 children. Considering only those with hearing loss >40 dB, prevalence was 2.0 per 1000—consistent with the prevalence estimates in other populations. We infer from these results that our extrapolation from the subset of children with complete examinations was sound. The more specific categorizations by severity and type of hearing loss shown in the Table provide a level of detail not usually available on a population level.
Maciej J. Wróbel
Department of Otolaryngology
Poznan University of Medical Science
1. Hyde ML. Newborn hearing screening programs: overview. J Otolaryngol. 2005;34(suppl 2):S70–S78
2. Cunningham M, Cox EOCommittee on Practice and Ambulatory Medicine and the Section on Otolaryngology and Bronchoesophagology. . Hearing assessment in infants and children: recommendations beyond neonatal screening. Pediatrics. 2003;111:436–440
3. Marazita ML, Ploughman LM, Rawlings B, Remington E, Arnos KS, Nance WE. Genetic epidemiological studies of early-onset deafness in the U.S. school-age population. Am J Med Genet. 1993;46:486–491
4. Szyfter W, Wróbel M, Radziszewska-Konopka M, Szyfter-Harris J, Karlik M. Polish universal neonatal hearing screening program-4-year experience (2003–2006). Int J Pediatr Otorhinolaryngol. 2008;72:1783–1787