Age related changes in hearing level among Thai people.

The present study was conducted to develop a normal aging curve in hearing of Thai people. The subjects were 805 males and 1110 females ranging in age from 7 to 89 years. Audiometric hearing threshold testing was performed at the frequencies of 1, 2, 4 and 8 kHz. Subjects with no evidence of hearing impairment were selected for hearing level analysis. The accepted subjects comprised of 1298 ears in males and 1818 ears in females with normal hearing. A normal aging curve of hearing level at each frequency was established by calculating the 25th, 50th, and 75th percentiles for each age group. The hearing threshold level gradually increased with age and rapidly over 50 years in both sexes, in particular at 8 kHz and 4 kHz. The results showed significant correlations between the hearing level and age. There were sex differences in hearing level at the 4 kHz from the age of 40. This normal curve established from subjects with no evidence of hearing problems may be useful for monitoring hearing levels of Thai people.