According to this study, researchers examined a three-fold increase in the elderly population of the world by the year 2050 has made hearing impairment (HI) the third most common disability in the elderly according to the statistics of the WHO. Moreover, the prevalence of HI has been on the rise in all age groups across the world.
On the other hand, HI, in addition to comprising 4.7% of the total causes of years lived with disability (YLD) in the world, imposes a great disease burden on the health system due to long-term social, functional, and psychological complications. In this cross-sectional study, 140 clusters each including 10 households from Tehran, Iran were sampled between 2012 and 2013 using cluster random sampling.
Trained audiologists examined the participants during face-to-face interviews. The hearing of the participants was evaluated before the removal of wax or other foreign bodies. In this study, HI was categorized as mild (grade 1, 26–40 db), moderate (grade 2, 41–60 db), severe (grade 3, 61–80 db), and deaf (grade 5, 81 db or more). All participants signed informed consent forms. The SATA software was used for data analysis.
The WHO has provided executive protocols for the collection of the data of hearing disorders in regional and provincial level, for epidemiologic studies on hearing and other ear disorders. In this study, for the first time in Iran and as the second country in the Middle East, we used the WHO protocol to evaluate the prevalence and causes of HI in an Iranian population.
According to our results, 14.7% of the society experienced some levels of HI and about two-thirds of them (9.9%) had mild HI. On average, the prevalence of HI in developed countries (4.9%) is much lower than its prevalence in Africa (15.7%) and South Asia (17.0%). A broad spectrum of diseases including genetic factors, pre and postnatal infections, otitis media, and foreign body cause hearing disorders in children and adults.
The sampling method is also important when evaluating HI in different societies; in our study, hearing evaluation was performed prior to the removal of wax or foreign body while this process has been performed after wax removal in many studies. Moreover, the type of the target population and other factors such as level of health care and lifestyle should also be considered when evaluating hearing problems.
In conclusion, the considerable occurrence of HI in Iran in comparison with other developing countries, with regards to the trend of aging in the population, seems concerning. This study is the first epidemiologic study of hearing loss in the national level and its results could be used as a baseline for other researches and evaluation of burden of HI in our country.