Epidemiology of permanent childhood hearing impairment in Trent Region, 1985-1993.

Abstract

This retrospective study of permanent childhood hearing impairment (PCHI) > or = 40 dB HL in children born between 1985 and 1993 and resident in Trent Health Region, achieved an ascertainment of 92.9% of that expected from previous studies and 100% for the subset of children born between 1985 and 1990. The prevalence rate of all permanent hearing impairment > or = 40 dB HL for the birth cohort 1985-90 is 133 (95% confidence interval, (ci) 122-145) per 100,000 live births (1 in 750). Sixteen per cent of PCHI were postnatally acquired, late-onset or progressive impairments. Excluding these, the prevalence rate for congenital impairments is 112 (ci 101-123) per 100,000 (1 in 900). The rate for profound impairments > or = 95 dB HL is 24 (ci 20-30) per 100,000 live births (1 in 4150). Prevalence was increased sixfold for children with a history of neonatal intensive care and 14-fold for children with a family history, compared with children with no risk factors. A more than two-fold increase in prevalence was seen in Asian children. For the congenitally-impaired children born between 1985 and 1990, 29% had a stay in neonatal intensive care > or = 48 hours, 30% had a family history of permanent childhood hearing impairment, and 12% had a cranio-facial abnormality (CFA). Over 59% were potentially detectable by a targeted neonatal screening programme using these three high-risk factors. For 1985-1993, the overall yield of the targeted neonatal screening programmes available in three of the 11 health districts was 15% but increased over time. The overall yield from the Health Visitor distraction test was 30% but lower in districts with neonatal screening programmes. Only 59% of children had a stated aetiology, classified by time of onset into genetic, including syndromes and CFA (41%), pre- or peri-natal (10%), post-natally acquired (6%), and uncertain onset (2%). Just under 40% of the children were said to have another clinical or developmental problem, about half of whom had at least two additional problems. The median age at referral, confirmation of the impairment, prescription of the hearing aid and fitting of the hearing aid were, respectively, 10.4 months, 18.1 months, 24.4 months and 26.3 months. A more severe impairment was associated with earlier age. Small improvements in the median age of hearing aid prescription and fitting were seen over time. Twenty-five per cent of children were referred for genetic counselling, the proportion increasing systematically with the severity of the impairment. Based on evidence of the yield from hearing screens we suggest a wider implementation of neonatal screening and further consideration of the role of the health visitor distraction test in the identification of children with PCHI. To facilitate further assessment of services for hearing-impaired children we suggest implementation of a co-ordinated shared list of children with permanent hearing impairment on a region-wide basis to provide adequate numbers for comparison over time, and the routine collection of a minimum set of data for each child.