Literature Review

Impaired vision an overlooked dementia risk factor


 

Impaired vision in older adults is an underrecognized and modifiable dementia risk factor, new research suggests.

Investigators analyzed estimated population attributable fractions (PAFs) associated with dementia in more than 16,000 older adults. A PAF represents the number of dementia cases that could be prevented if a given risk factor were eliminated.

Results showed the PAF of vision impairment was 1.8%, suggesting that healthy vision had the potential to prevent more than 100,000 cases of dementia in the United States.

“Vision impairment and blindness disproportionately impact older adults, yet vision impairment is often preventable or even correctable,” study investigator Joshua Ehrlich MD, assistant professor of ophthalmology and visual sciences, University of Michigan, Ann Arbor, said in an interview.

Poor vision affects not only how individuals see the world, but also their systemic health and well-being, Dr. Ehrlich said.

“Accordingly, ensuring that older adults receive appropriate eye care is vital to promoting health, independence, and optimal aging,” he added.

The findings were published online in JAMA Neurology.

A surprising omission

There is an “urgent need to identify modifiable risk factors for dementia that can be targeted with interventions to slow cognitive decline and prevent dementia,” the investigators wrote.

In 2020, the Lancet Commission report on dementia prevention, intervention, and care proposed a life-course model of 12 potentially modifiable dementia risk factors. This included lower educational level, hearing loss, traumatic brain injury, hypertension, excessive alcohol consumption, obesity, smoking, depression, social isolation, physical inactivity, diabetes, and air pollution.

Together, these factors are associated with about 40% of dementia cases worldwide, the report notes.

Vision impairment was not included in this model, “despite considerable evidence that it is associated with an elevated risk of incident dementia and that it may operate through the same pathways as hearing loss,” the current researchers wrote.

“We have known for some time that vision impairment is a risk factor for dementia [and] we also know that a very large fraction of vision impairment, possibly in excess of 80%, is avoidable or has simply yet to be addressed,” Dr. Ehrlich said.

He and his colleagues found it “surprising that vision impairment had been ignored in key models of modifiable dementia risk factors that are used to shape health policy and resource allocation.” They set out to demonstrate that, “in fact, vision impairment is just as influential as a number of other long accepted modifiable dementia risk factors.”

The investigators assessed data from the Health and Retirement Study (HRS), a panel study that surveys more than 20,000 U.S. adults aged 50 years or older every 2 years.

The investigators applied the same methods used by the Lancet Commission to the HRS dataset and added vision impairment to the Lancet life-course model. Air pollution was excluded in their model “because those data were not readily available in the HRS,” the researchers wrote.

They noted the PAF is “based on the population prevalence and relative risk of dementia for each risk factor” and is “weighted, based on a principal components analysis, to account for communality (clustering of risk factors).”

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