Nearly 20 percent of dementia cases could be prevented through better eye health: Study

Nearly 1 in 5 dementia cases could be associated with vision impairment, according to a study published Thursday, suggesting better eye health could help to lower the diagnosis rate.

Dementia does not refer to a specific disease but is a general term for the impaired ability to recall, think or make decisions that inhibit daily tasks, according to the Centers for Disease Control and Prevention (CDC). The most common type of dementia is Alzheimer’s disease.

About 5.6 million Americans 65 and older have Alzheimer’s or related dementia, the study found.

Overall, up to 19 percent of dementia cases were associated with at least one vision impairment, researchers from the Johns Hopkins University School of Public Health found.

This was slightly higher among participants aged 71-79, women and non-Hispanic white people, according to the research, published in the medical journal JAMA Ophthalmology. This follows past research showing women are nearly twice as likely to be affected by Alzheimer's disease than men, primarily due to women living longer.

Researchers noted their findings do not prove a “cause-and-effect relationship.” In other words, the “total contribution of late-life-vision impairment to dementia may be substantial.” This warrants further research, which could lead to new dementia prevention strategies, they wrote.

“Importantly, more than 90% of vision impairments are preventable or correctable,” researchers wrote.

To conduct the research, the team looked at data from 2,767 American adults aged 65 and older in 2021. Participants underwent cognitive exams and testing for three types of visual impairment including near acuity, or one's ability to see close objects; distance acuity, or one's ability to see small details in the distance; and contrast sensitivity, or one's ability to perceive sharp and clear outlines of very small objects.

About 5 percent of dementia cases were connected to vision impairment related to distance acuity, nearly 10 percent to near acuity, and 15 percent to contrast sensitivity, per the findings.

Researchers have long studied the causes of dementia and what can be used to prevent it.

A study released in July found Ozempic, a medication used for diabetes and weight loss, may reduce dementia. The findings, however, cannot be applied to users who do not have diabetes.