By Christa Lesté-Lasserre

Older adults who start losing both vision and hearing may be at an increased risk of developing dementia.

Gihwan Byeon at Kangwon National University Hospital in the South Korea and his colleagues studied 6250 people, aged 58 to 101, over six years. At the start of the study, they asked each person to rate his or her own ability to see and hear. The participants also underwent cognitive testing every two years.

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The team found that 7.6 per cent of those reporting both vision and hearing loss had dementia at the start of the study, and another 7.4 per cent developed it within six years.

Meanwhile only 2.4 per cent of people with only vision loss or hearing loss had dementia at the start of the study, and another 2.9 per cent developed it by the end of the study.

Adjusting for other factors that influence dementia, such as sex, education and income, the researchers estimate that people with impairments of both vision and hearing are twice as likely to develop dementia as people with only one or neither impairment.

The results are “very tantalising,” says Jason Warren at University College London, who was not involved in the study. However, the findings must be considered with caution, he adds, as the hearing and vision loss were self-reported and not measured directly.

Even so, this could provide insight into the cognitive decline that people with hearing and vision loss experience, says Warren. “We see and hear with our brains, and the first sign of a failing brain in dementia may well be an inability to navigate the complex sensory environments of everyday life,” he says.

Byeon wonders whether the brains of people with both hearing and vision loss might struggle to compensate for the lost senses. Usually, people with impaired vision develop better hearing to compensate, and people with impaired hearing rely more on their vision to help out, he says. “Dual sensory impairment may not be compensated for, making [the brain] more vulnerable to dementia,” he says.

Journal reference: Neurology, DOI: 10.1212/WNL.0000000000011845

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