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Scientists Say That Up to 20% of Dementia Cases May Be Prevented

According to recent study, blurry vision may be linked to dementia in as many as 1 in 5 cases. By focusing on visual impairment, these findings may pave the way for novel approaches to dementia prevention.

Going by data from the U.S. Centers for Disease Control and Prevention from 2014, more than 5 million Americans over 65 suffer from dementia. Alzheimer's disease is the most prevalent type of dementia, which is typified by a decline in memory, thinking, and decision-making skills.

The exact cause of dementia is unknown, however a number of environmental and genetic risk factors have been linked to the illness.

Hearing loss has previously been linked to cognitive decline and a higher chance of developing dementia. The links between dementia and vision loss, which affects around one-third of the elderly population, have not, however, received as much research attention.

Researchers from Johns Hopkins University examined data from 2,767 American individuals 71 years of age or older for a recent study that was published in the journal JAMA Opthalmology. The data set, which included a nationally representative cohort, was gathered in 2021.

In addition to cognitive testing, participants were tested for three types of visual impairment: contrast sensitivity, which is the capacity to distinguish distinct and distinct outlines of small objects, near acuity, which measures how well a person can see objects up close, and distance acuity, which measures how well a person can see objects far away.

The researchers calculated that at least one form of visual impairment may be responsible for 19% of dementia cases overall, with poor contrast sensitivity exhibiting the highest correlation.

"The results from this cross-sectional study suggest that nearly 1 in 5 prevalent dementia cases in community-dwelling US adults aged 71 years or older could have at maximum been avoided if vision impairment had been eliminated," the researchers write. "Overall, these data support the inclusion of sensory impairments as potentially modifiable risk factors for dementia prevention strategies."

The study found that up to 90% of visual impairments are avoidable or treatable.

Naturally, these results are based on correlations, therefore we are unable to establish a direct link between dementia and visual impairment. Nevertheless, given this high correlation, vision loss should be considered while developing dementia prevention methods.

"Although the study is limited by its cross-sectional design and small sample size, the findings provide unique value regarding the burden of dementia associated with vision impairment,"

Mingguang He and Xianwen Shang, two experts in ophthalmology at The Hong Kong Polytechnic University in China who were not involved in the research, said in a commentary published alongside the study, "vision impairment deserves scrutiny as an intervention priority for the prevention of dementia in older adults."