A. SPECIFIC AIMS

INTRODUCTION

The principal focus of this application is to obtain resources to collect detailed audiometric data on the

adolescents enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). ALSPAC was

specifically designed to determine ways in which the individual's genotype combines with environmental

exposures and experiences to influence health and development (Golding 2001). Its strengths include use of a

total population sample unselected by disease status, and comprehensive data on children's physical, mental

and behavioral health, family and social circumstances and environmental features. In addition, a DNA bank

has been established on over 10,000 mothers and children with consent for undisclosed genetic analysis

(Pembrey 2004). ALSPAC is, therefore, uniquely positioned to explore genetic and environmental determinants

of common diseases and impairments.

Hearing loss is the commonest sensory deficit in developed countries(Davis 1989, Smith, Bale & White 2005.)

The cumulative prevalence of hearing loss in any population rises through the lifespan (Russ 2001). Hearing

loss and hearing function have been most closely studied at the extremes of life- in the neonatal period and in

old age. However, there have been very few population studies of hearing function in adolescence and even

fewer opportunities to examine the relationship between environmental factors such as otitis media, early life

risks and noise exposure and later hearing function. Similarly, very few studies have attempted genotypephenotype

correlations with respect to hearing function on a large population-based cohort, especially in

adolescence. To our knowledge, the detailed data we propose to collect on hearing in the ALSPAC 17-18 year

cohort would be the first opportunity to link detailed hearing phenotype data with genotype data on a

representative population-based sample of adolescents.

There is growing interest in the hearing function and abilities of adolescents. Widespread use of personal

listening devices such as iPods and MP3 players has heightened awareness of the potential vulnerability of

this population to the extremes of noise exposure from modern devices using current compression algorithms

(Fligor and Cox 2004). (reference - Output levels of commercially available portable compact disc players and

the potential risk to hearing.Fligor BJ, Cox LC Ear Hear. 2004 Dec;25(6):513-27)... Earler survey-based U.S.

data suggest that up to 3.4% 18-34 years olds self-report hearing problems ( NHIS 1990), while the US

National Health and Nutritional Examination Survey (NHANES) III documented 14.9% 6-19 year olds with

unilateral or bilateral losses greater than 16dBHL at low or high frequencies. (Niskar et al.1998). Consequently, we are

moving from a conceptualization of adolescence as a time when hearing is essentially intact, to one in which

considerable variations in hearing ability begin to emerge in the population. Hearing ability at any age will be

sensitive to the effects of multiple risk and protective factors, both genetic and environmental.