Up to one in five dementia cases linked to eyesight issues

Scientists have estimated the proportion of dementia cases that are associated with vision impairment within the US population.

As part of the JAMA Ophthalmology study, researchers analysed data from a national representative longitudinal study of 2767US adults aged 71 and older.

The scientists used the strength of the association between visual impairment and dementia to estimate the proportion of dementia cases that could be attributed to three different types of vision impairment – affecting near visual acuity, distance visual acuity, and contrast sensitivity.

Overall, the study estimates that around 19% of dementia cases within the population can be attributed to at least one form of vision impairment.

The researchers found that contrast sensitivity was most commonly linked to the development of dementia, with around 15% of dementia cases attributed to impaired contrast sensitivity.

Impaired distance vision was associated with 5% of dementia cases, while 10% of dementia cases were linked to impaired near vision.

“Contrast sensitivity was associated with the largest PAF [population attributable fraction], indicating the total impact of vision impairment on dementia should be quantified using measures beyond just distance visual acuity.

“Overall, while not establishing a cause-and-effect relationship, these findings support considering vision health in dementia prevention strategies aimed at reducing modifiable risk factors,” the researchers highlighted.

The authors emphasised that vision impairments often arise from conditions that are reversible ­– such as cataracts or uncorrected refractive errors.

“Our analyses provide additional support to address vision impairments globally, where up to 90% are estimated to be preventable or correctable,” the researchers stated.