Background

For the purposes of hearing assessment, thresholds to air conducted and bone conducted stimuli are converted into comparable units, dBHL at each frequency. This calibration of air and bone- conducted stimuli allows for comparison between air and bone conduction hearing thresholds. The difference between the air conduction threshold and the bone conduction threshold is termed the "air-bone gap" and generally indicates the presence of a conductive (i.e affecting the outer or middle ear) hearing loss. However air and bone conduction thresholds for infants with normal hearing using physiological measures have identified an air-bone gap in the low frequencies that does not result from conductive hearing losses but rather from maturational difference and sensitivity (Small and Stapells 2008 and Vander Werff et al. 2009). Studies to date have suggested that this maturational air bone gap exists up to 3 years of age on both physiological and behavioural studies, however studies specifically examining the patterns of behavioural air conduction and bone conduction thresholds in children older than 3 years of age have not been carried out. It is therefore not known if the maturational air-bone gap exists in children older than three years of age and at what stage it starts to close.

Research Questions:

1. Does a maturational air-bone gap exist in the ALSPAC cohort at age 5, 7, 9 and 11 years?

2. If a maturational air-bone gap is found to exist, at what age does this close/ reduce?

3. Are there frequency dependent trends in behavioural air and bone conduction thresholds for children aged 5, 7, 9 and 11 years?

Objectives:

1. Describe the air conduction hearing thresholds for each stimulus frequency at age 5, 7, 9 and 11.

2. Describe the bone conduction hearing thresholds for each stimulus frequency at age 5, 7, 9 and 11.

3. Identify if there are a) age and b) frequency dependent trends in air conduction and bone conduction hearing thresholds across the different age groups.

4. Quantify the air-bone gap at each age and examine changes over time.

Hypothesis:

It is hypothesised that the air-bone gap decreases with age.

Exposure variable(s): Age of child

Outcome variable(s): Air conduction and bone conduction hearing thresholds

Confounding variable(s): Sex and socioeconomic status.