Current status and future trends of deafness and hearing impairment in the tropics

ABSTRACT

Hearing is the sense upon which human communication depends and deafness and hearing impairment are preventable disabilities. These scourges are on the rise in the tropical countries. Until 1985, even the W.H.O. did not take notice of these handicaps. Following the resolution passed by the 38th world health assembly in 1985, and then by the 48th assembly in 1995, combined with the remarkable endeavour of the E.N.T. fraternity, a permanent office was established in Geneva. This office instantly began a war against the hearing handicap under the title of 'PDH'. The Manchester symposium of 1995 must be called a watershed in this field, bringing many otologists and audiologists on one platform. However much needs to be done. The global estimates inform us that 2.2% of the world hearing handicapped. In the developing world the mangnitude of the problem is much more than the developed world. According to the world bank 70% of the burden of sickness is produced by communicable infections in Sub-Saharan Africa. The figures may match in the Indian subcontinent, where typhoid, meningitis and tuberculosis are significant contributors to human misery. In Latin America these communicable infections affect about 40% of the population. In sharp contrast to these figures only 15% are affected in the developed world. Even that figure is much too high, as the world's economic resources continue to shrink. The prevalence of hearing impairment varies between the countries in the developing world. For instance it is 10% in India, 9.3% in Myanamar, 6.5% in Nepal, 6% in Thailand and roughly 11% in Pakistan. In Africa the prevalence varies between 7% -10%. No data is totally reliable, as the standardization of methodology, and sensitivity as well as specificity of the data remain to be validated by the global community. While it is the young population that seems to bear the brunt of the problem in the developing world, it is the ageing population that is mostly affected in the west, even the causes are significantly variable. For instance, Muslims of the Arabo-African region and many Asian countries are allowed, indeed encouraged to customarily marry within the tribes, preferably cousins. The Hindus are not allowed to do so thus, consanguinity is an important cause of congenital deafness in the Muslim population stretching from the Mediterranean Libya through most of Africa, the entire Middle East, Indo-Pakistan subcontinent, the Asia-Pacific countries like Indonesia, Malaysia, Bangladesh, a part of the Philippines and the distant rich Sultanate of Brunei. The genes are autosomal recessive and not dominant as was proved in a study conducted in Pakistan while maternal rubella is a prominent cause in the west, it may not be so in the Indo-Pak subcontinent. Ototoxicity, on the other hand, is a universal problem, but its causes vary from country to country. For instance aminoglycosides and loop diuretics are the major causes in the Asian region, while 'Cassawa' seems to be the major culprit in Africa. The common causes established uniformally in the developing world are1. communicable infections, 2. Otitis Media 3. Ototoxicity 4. Consanguinity 5. Malnutrition, and 6. Noise what is needed is [A] Population based surveys to establish the true nature of the problem [B] Awareness of the health personnel, NGOs and the community, [C] Early Intervention [D] Primary Ear Care [D] Prevention from complications [E] Rehabilitation and Rechannelization into the normal human pool. But all these objectives are not easy to attain. Population explosion, illiteracy, poverty, economic constraints and worst of all lock motivation are some of the crippling obstacles. This presentation looks at the epidemiology in some of the countries in the developing world, highlights the salient causes of hearing handicap and evaluates the strategies desired to combat the menace of deafness and hearing impairment in the tropics