People with hearing loss who cannot cope with a hearing aid have an increased risk of dementia. This is the conclusion of a study by Fan Jiang cs published in The Lancet Public Health.
The researchers analyzed data from 437,704 people who were part of the UK Biobank database. The mean age of the participants at the start of the study was 56 years and the mean follow-up time was 12 years. About three quarters of the participants (325,882) had no hearing loss and the remaining quarter (111,822) had some hearing loss. Of those with hearing loss, 11.7 percent (13,092) used a hearing aid. The researchers also analyzed how other factors, including loneliness, social isolation and depressive symptoms, may influence the association between hearing loss and dementia. Their conclusion: 8 percent of dementia cases can be prevented with the proper use of hearing aids.
This is not a new finding, note commentators Gill Livingston and Sergi Costafreda. But that has now been established with this large cohort study. More focused randomized, placebo-controlled studies are not possible for ethical reasons: you simply cannot deny people with hearing problems the use of a hearing aid.
It is not clear why hearing aids have a protective effect on cognitive decline and dementia. It is possible that persons with hearing loss experience a higher cognitive load, which can be accommodated by the use of a hearing aid. Sensory deprivation could also play a role: in that case, hearing loss leads to structural changes in the primary auditory cortex, the right temporal lobe, or perhaps even the entire brain. These changes could in turn lead to cognitive decline. Furthermore, indirect effects are obvious: people with hearing loss, especially the elderly, are more likely to experience social isolation and depression than their peers without hearing loss. And it is precisely those types of psychosocial problems that we know give rise to an increased risk of cognitive decline. Remarkably, however, Jiang et al.’s study found that less than 11 percent of the association between hearing aid use and reduced risk of dementia was mediated by improvement in psychosocial problems. Apparently, the hearing aids mainly have a direct effect, whatever that is.