DDT residues in a vineyard soil after 24 years of exposure.
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Chromatography, Gas↗
Biomedical subjects
A C Davis
Publications and source records attributed to A C Davis.
Population-based genetic study of childhood hearing impairment in the Trent Region of the United Kingdom.
The objective of the study was to investigate childhood hearing impairment in a population-based sample from a genetic perspective. Participants included 82 families with hearing-impaired children (aged 4-13) previously ascertained in the Trent Health Region. A questionnaire was mailed to all families, followed by a home visit and Connexin-26 35delG mutation screen. The Connexin-26 35delG mutation was identified in seven families (approximately 10 per cent of non-syndromal hearing impairment). Children of these families were significantly more likely than children with other modes of inheritance to have a profound hearing loss with a flat audiogram profile. The families of children with a significant admission to a neonatal intensive care unit were significantly less likely to have had genetic counselling. Eight families visited were found to have features suggestive of a genetic syndrome that had not been previously assigned a specific diagnosis. The study concluded that hearing-impaired children should be investigated systematically according to an agreed-upon protocol, which should include Connexin-26 35delG mutation analysis at least for those with severe-to-profound hearing loss.
Adolescent↗
The distribution of hearing threshold levels in the general population aged 18-30 years.
Hearing threshold levels at audiometric frequencies between 0.25 and 8 kHz were obtained by manual audiometry using 5-dB steps in adults aged 18-30 years, as part of a large random survey of hearing in the UK. After screening to ensure otological normality, including careful analysis of any noise exposure history, the median thresholds of the 241 screened subjects deviated from audiometric zero by an average of 4.3 dB over the frequencies from 0.5 to 4 kHz in the direction of poorer hearing. Even greater deviations were evident at 0.25, 6 and 8 kHz, consistent with the discrepancies between normal hearing threshold and ISO 389 standard reference zero that have been reported previously. Within the age band from 18 to 30 years, age did not influence hearing threshold levels. Socio-economic status defined by occupational group (manual or non-manual) had a significant effect at frequencies up to 2 kHz, with those in non-manual occupations having better hearing than those in manual occupations by an average of 2.4 dB, despite screening for middle-ear disease, noise exposure and other possibly confounding factors. In a screened sample, males had better hearing threshold levels than females, but this difference was sensitive to screening criteria. The unscreened sample had median hearing threshold levels that were at most 2 dB worse than the screened sample across the frequency range.
Adolescent↗
Transient-evoked otoacoustic emissions in a representative population sample aged 18 to 25 years.
Transient-evoked otoacoustic emissions (TEOAEs) were obtained from 688 ears of a group of 345 young adults aged 18 to 25 years, using the Otodynamics ILO88 in the standard, non-linear mode. Normative data for TEOAEs obtained from 186 otologically normal (ON) ears are presented. In 5 ON ears, there was no recordable response, despite hearing threshold levels better than 20 dB. The main factors affecting the TEOAE level were (1) gender, where females had larger responses on average than males; (2) tympanometric measures, where ears with entirely normal tympanometric measures had larger responses than those with minor tympanometric abnormalities; (3) click stimulus intensity measured in the ear canal, which correlated positively with TEOAE level; and (4) hearing threshold level at 0.5 kHz, which correlated negatively with amplitude. There was also a small effect of social noise exposure in the 2-kHz region of the TEOAE, where the response was lower in those subjects exposed to significant social noise.
Acoustic Impedance Tests↗
Epidemiology of permanent childhood hearing impairment in Estonia, 1985-1990.
This paper describes a retrospective study of permanent childhood hearing impairment (PCHI) > or = 40 dB HL in the better ear in children born between 1985 and 1990 and resident in Estonia. The prevalence rate of all permanent hearing impairment for the birth cohort 1985-1990 was 172 (95 per cent (CI 151-194) per 100,000 live births and that of congenital impairment was 152 (CI 134-170) per 100,000. For the congenitally-impaired children, 11 per cent had stayed in a neonatal intensive care unit for 48 hours or more, 2 per cent had a craniofacial abnormality, and 31 per cent had a family history of PCHI. As for aetiology, hereditary causes were stated most frequently in 36 per cent of all of the cases of PCHI. The aetiology remained unknown in 34 per cent of cases. Additional disabilities were found in 23 per cent of all cases. Specific syndromes were recognized in 2 per cent of hereditary cases. The mean age at the confirmation of hearing impairment was 46.4 months and at hearing aid fitting 57.0 months. The results were compared with other European studies, particularly the Trent study.
Child↗