Prior research has found that there may be a connection between hearing loss in aging people and the onset of dementia. In a new study, a team of health care researchers and geriatric specialists affiliated with Johns Hopkins Bloomberg School of Public Health, the University of Michigan and the Duke University School of Medicine surveyed patient health care records and reported that approximately 1 in 5 cases of dementia could also be attributable to vision impairment in community-dwelling U.S. adults aged 71 years or older.

The paper is published in the journal JAMA Ophthalmology.

Scientists still do not know what causes dementia, but they strongly suspect that it might be tied to several factors, one of which might be sensory degradation. As the senses lose their sharpness, the hypothesis proposes, the brain must work harder to make sense of the external environment, all while undergoing its own aging process.

The result could be loss of cognitive and memory abilities. In this new effort, the researchers looked for such evidence in people over the age of 71 who have experienced at least one of three main types of vision impairment: near or distance acuity, or contrast sensitivity.

The research team studied data on 2,767 people in the U.S. that were alive in 2021 and over the age of 71. For each person studied, the team looked for any evidence of vision loss or mental decline.

They found that approximately 19% of dementia cases could be attributable to one or more types of vision loss. This, they note, suggests that dementia could have been prevented in nearly 20% of cases if loss of vision had been addressed. They note that prior studies have shown that approximately 90% of vision problems in older people are correctable through glasses or surgery.

The research team acknowledges that their results are based on associations rather than proof because there is no way to prove any single cause of dementia. But they also suggest that the associations they found make a strong case for it.