Abstract
Hearing loss is a marker of risk for cognitive decline and dementia. Controlled hearing intervention studies of long-term cognitive outcomes are challenging, and thus the evidence for the impact of hearing interventions is primarily from observational studies and will likely continue to be from studies other than randomised controlled trials. Seven studies of hearing interventions with cognitive outcomes assessed over longer than 3 years are reviewed. Most were of low-to-moderate quality. One cochlear implant study had indeterminate findings. Of six hearing aid studies, three reported a positive impact of hearing aid use while three reported no impact of hearing aid use on cognitive decline or incident cognitive impairment. Further studies are required to elucidate the benefit of hearing interventions on long-term cognitive outcomes. Research should include objectively ascertained hearing data, theoretically motivated cognitive outcomes including dementia subtypes, characterisation, and control for confounds and application of advanced statistical modelling to test causal hypotheses.