Bajaj, Y.; (2007) Causes of deafness in East London Bangladeshi children. Doctoral thesis , University of London.

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Abstract

The aim of this study was to examine the causes of sensorineural hearing loss in the Bangladeshi population resident in East London. Almost all of this population originates from Sylhet, a province in Bangladesh. The study was conducted at a community based audiology clinic and tertiary level genetics department. One hundred and fifteen families (134 patients) were ascertained 11 families declined to participate and 4 families could not be contacted. All children of Bangladeshi ethnic origin with bilateral sensorineural hearing loss more than 40dB in the better hearing ear were included in this study. Information on all these patients was collected from their case notes. For the 67 patients in whom the cause of deafness was not clear from the records or unknown (or non- syndromic deafness), families were seen in the research clinic. The prevalence of deafness >40db in Bangladeshi children under 16 years of age in East London was calculated to be approximately 3.86 per 1000 (95%CI: 3.24, 4.47). This is nearly 2.3 times the national average. Parents were consanguineous in 35 out of 105 families (33.3%) in which this information was available. On calculating the prevalence of deafness in the Bangladeshi children belonging to non-consanguineous families, the prevalence falls to 2.72 per 1000 (95%CI: 2.10, 3.34). Genetic causes appear to be the most common cause of deafness in Bangladeshi population in 59.6% patients. Environmental causes were responsible for hearing loss in 18.5% patients and in 21.8% cases the cause of deafness was undetermined. Of the deafness due to genetic causes, 57.7% were non-syndromic, 25.3% syndromic and 16.9% were chromosomal. The single most common cause of sensorineural hearing loss in the Bangladeshi population in this study was due to mutations in the GJB2 gene (Connexin 26) in 14 of these families. The mutations in GJB2 in this population were W24X, IVS1 + 1G->A, M1V, V95M and W77X. W24X was the most common mutation seen in 40% (8/20) patients. Genetic causes are the common cause of deafness in subjects of Bangladeshi origin and 29.8% children with non-syndromic deafness were positive for mutations in GJB2.

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