LONDON -- Hearing impairments are far more prevalent among learning-disabled individuals than in the population at large, and the combination may have a negative impact on development and mental health, Dr. Helen Miller said at the Seventh World Congress on Innovations in Psychiatry.
Concurrent deafness and learning disability frequently delay the diagnosis and appropriate management of one or the other condition, said Dr. Miller of National Deaf Services, London.
That learning disability increases the risk of hearing impairment more than 10-fold has been confirmed by several studies. The prevalence is 0.1%-0.8% in the general population, while most surveys of learning-disabled individuals find that 10% are moderately hearing impaired or deaf.
The risk rises with the degree of intellectual disability: One survey found that 40% of those who were severely disabled were hearing impaired, Dr. Miller said.
In part, the concurrence reflects the influence of conditions that cause both intellectual and auditory deficits. These conditions include prenatal CNS infection (for example, rubella and cytomegalovirus); obstetrical complications such as anoxia; and genetic disorders such as Down syndrome.
Half of children horn to mothers who had rubella between the 8th and 16th week of gestation had hearing impairment in one survey and 25% were diagnosed with learning disabilities at ages 89 years.
In Down syndrome, hearing loss can be progressive, the result of repeated infections due to anatomical anomalies, Dr. Miller said.
Generally, lack of language experience early in life can have lasting consequences. The risk is enhanced in individuals who are learning disabled because deafness may exacerbate limitations in speech development, …