Our sensory systems are constantly bombarded by information from the environment, yet despite this multisensory stimulation we maintain a coherent perception that allows us to efficiently interact with our world. The solution to this everyday problem critically depends on the brain binding together the appropriate, task-relevant, sensory inputs whilst ignoring other sensory information. Multisensory integration is a fundamental process by which the brain combines and transforms relevant sensory information into a meaningful percept that is, in turn, critical for higher cognitive, social and physical functions. Our previous research suggests that multisensory integration is affected by the ageing process and, moreover, that inefficient integration is associated with reduced physical health and cognition. Building on these findings, the aim of the proposed research is to provide evidence for a causal link between inefficient multisensory integration and age-related declines. To that end, we have embedded a novel measure of multisensory function into a nationally-based, longitudinal study, “The Irish Longitudinal study of Ageing” (TILDA), offering us the unique opportunity to measure multisensory function in a large, representative sample of over 4,000 older adults. Using these data, we will first identify individual differences in multisensory function as a function of age (i.e. cross-sectional analyses), as well as changes in multisensory function with increasing age (i.e. longitudinal analyses). Thus, for the first time, we will provide normative data on multisensory function across older age. Second, we will conduct analyses of co-morbidities associated with changes in multisensory function, particularly physical health related to the risk of falls, such as gait and cardiovascular measures, as well as assessments of cognition, such as attention, memory and spatial reasoning. The findings will provide novel insights into how perceptual function underpins physical and cognitive health during ageing and may provide an early marker of decline in different domains.