Prevalence of prelingual deafness in Italy.

Neonatal hearing loss is the most frequent sensorial congenital defect in newborns. No data are available on worldwide prevalence of congenital deafness. World Health Organization (WHO) data indicate 1-4 cases per 1000 individuals, with a considerable increase in developing countries. A prevalence exceeding 1 per 1000 however, indicates a serious public health problem calling for urgent attention. Aim of the study was the evaluate the prevalence of prelingual deafness in the Italian population and determine the socio-demographic characteristics of the condition. Data were provided by the National Institute of Social Insurance (INPS) and the Italian Central Statistics Institute (ISTAT) and were collected in 18 out of the 20 Italian regions (98.2% of total population). All subjects recognized as deaf-mute by a special medical committee were included. According to law No. 509/1988, they had to present a mean bilateral sensorineural-hearing impairment, detected in neonatal age, which caused the damage in speech development and equal to 60 dB or more for 500-, 1000- and 2000-Hz frequency tones in the better ear. Prevalence rates were calculated according to region and age bracket using updated population data from census 2001. Statistical analyses were performed using the SPSS statistical software package. A total of 40,887 cases of prelingual profound sensorineural hearing loss > or =60 dB were detected in Italy in 2003, for a total prevalence rate of 0.72 per 1000. The hearing impairment prevalence differs according to sex. The overall prevalence is 0.78 per 1000 for males and 0.69 per 1000 for females (p < 0.001). The hearing impairment prevalence differs according to region of residence (p < 0.001). The geographic distribution of prelingual deafness was found to be: North 15,644 cases (0.63 per 1000), Central Italy 7111 cases (0.64 per 1000), South and Islands 18,132 (0.87 per 1000). The prelingual hearing loss is highly prevalent in South Italy (Basilicata, Calabria and Sicily). For the southern regions of Italy, the rate observed in the 50-64 and >64 age groups reached 1.27 and 1.15, respectively. This phenomenon may have been due, in part, to the epidemic incidence of maternal rubella which occurred in the 40's and 50's (in Italy, the rubella vaccination was only recommended starting from 1972), and, in part, to the habit of contracting consanguineous marriages. Data from the Vatican Archives on 520,492 consanguineous marriages, for which dispensation was requested in the period 1911-1964, indicate that in the years 1935-1939, in small villages in South Italy (Basilicata, Calabria, Sicily) consanguineous marriages accounted for over 40% of marriages.