Frequency of hearing loss in a series of rural communities of five developing countries located along the Silk Road

Hearing loss (HL) affects millions of people worldwide. While epidemiological data from Western countries are already available, this information is still lacking for many developing countries and rural communities. Here we report, for the first time, a study on the frequency of HL in a series of rural communities located along the Silk Road. Study design: Four hundred and ninety-six subjects (236 males and 260 females ranging from eight to 84 years of age) selected in non-random, convenience samples from rural communities belonging to Terra Madre Organization have been enrolled: 228 from Georgia and Azerbaijan (Caucasus region), 151 from Uzbekistan and Kazakhstan (Central Asia), and 117 from Pair (Tajikistan). Subjects underwent pure-tone audiometry at 0.25, 0.5, 1, 2, 4, 6, and 8 kHz; pure-tone average (PTA) values were determined. Results: The overall HL frequency, ranging from 9% to 18%, in the investigated communities located along the Silk Road is higher than that reported for WHO European region countries but comparable with that reported for WHO South-East Asian region countries and other developing countries. Interestingly, with regard to the impact of age, two different disease behaviours have been identified in all the tested communities – one for males and the other for females. In females HL starts at all PTAs between 30 and 40 years of age. In contrast, in males age starts to affect hearing at high frequencies in young adulthood (20–25 years old), but later (50–60 years old) at low and medium frequencies. Conclusion: Despite the difficulty in reaching rural communities, mainly located in remote places, and the need to perform further studies using a larger sample size, recent data provide new information and will contribute to a better definition of HL worldwide frequency.