Loss of hearing is common, and tends to increase over the life course, affecting over 10 million people in the UK. Although there have been many studies concerning deafness in childhood, very few have examined the normal course and variation in hearing in a large population of individuals from an early age into mid and older adulthood. This is troubling since even low levels of hearing loss can result in failure to hear speech clearly, and can impact social communication, mental health and employment. Moreover hearing loss is associated with cognitive decline, and has been identified as one of the nine modifiable risk factors in the Lancet Commission on Dementia. It is not known whether hearing loss is a causal factor for cognitive decline, or a non-causal feature associated with ageing and neurodegeneration. Monitoring hearing in a population from early in life, and using novel genetic methods to investigate causality, may be crucial to understanding not just the role of hearing in cognitive function, but also the ageing process in general.

Utilising the Avon Longitudinal Study of Parents and Children (ALSPAC), this project will be the first to study, in depth, the changes in hearing ability over the life-course from early childhood to age 30 and to examine the relationship with cognitive function.

Firstly we will analyse data from approximately 5000 individuals, for whom we have detailed measures of hearing function at ages 7, 9, 11 and 14, and which we will collect again when they are age 30. We will characterise how their hearing has changed from age 7 to age 30, and identify those with who have experienced a drop in hearing ability. We will examine whether changes in hearing are associated with environmental exposures or the presence of particular genes.

Secondly we will analyse their cognitive function, using measures of memory, attention and processing speed collected at age 8, 10, 13, 15 and 24, and which we will collect again at age 30. We will compare trajectories in hearing ability with trajectories of cognitive function from age 7 to age 30, and test whether those who experience a decrease in their hearing ability are more likely to have poorer processing speed, attention and working memory at age 30.

The project is unique in that:
• it will provide observational information on the natural history and genetic influences on hearing over the first 30 years of life
• it will be the first to assess age-related relationships between changes in hearing and features of cognition through childhood into early adulthood

The information collected will be valuable for studies of further ageing of this population as well as identifying possible mechanisms linking hearing and cognition.