Prevalence of hearing loss at the age of 15 in a birth cohort of 12 000 children from northern Finland.

Hearing losses at the age of 14 years were investigated in a questionnaire administered to 11 780 children born in northern Finland and followed up since pregnancy. The untraced cases numbered 20, or 1.7 per 1 000. Audiometry screening results from the schools were obtained from 97.2% of the 425 children who were reported to suffer from hearing loss and a random sample of 959 children with normal hearing. When the figures were calculated to represent the whole material of 11 748 cases, marked hearing loss, PTA greater than 25 dB in the better ear, was found in 64 children, 0.5%, minor loss, greater than 20 dB at 4 kHz but PTA less than 25 dB in the better ear, in 420 children, 3.6%, and slight abnormality, greater than 20 dB, at any frequency in 1 224, 10.4%. 17.6% of the boys and 11.8% of the girls had some kind of hearing loss. Eight children were deaf in both ears and 11 in one ear, and 16 children were severely impaired in at least one ear (PTA greater than or equal to 60; less than 90 dB).