Hearing loss is associated with accelerated cognitive decline in older adults and has been identified as a modifiable risk factor for dementia. Hearing loss makes the largest single contribution to the identified potentially modifiable risk factors, yet is the factor that has received the least scientific attention. Whether treatment of hearing loss can delay the onset of cognitive decline is currently unknown, due to limitations in the methodology and data of studies to date. This presentation will discuss an ongoing longitudinal study investigating the effect of hearing aid use on cognitive decline. We expect this study will provide rigorous evidence of the effects of treatment of hearing loss on cognition in older adults over time.