Impaired near-range vision may speed older adults’ rate of mental decline as they age, study findings suggest.

Researchers at the University of Texas Medical Branch in Galveston found that among more than 2,000 elderly Mexican Americans, those with significant impairments in their near vision tended to show a steeper decline in mental functioning over 7 years.

The reason for the link is uncertain, but poor close-range vision may limit older adults’ activities - including mental “exercises” like reading and crossword puzzles - and thereby contribute to cognitive decline, according to Dr. Carlos A. Reyes-Ortiz, the study’s lead author.

In addition, he said a lack of “visual stimulation” to the brain may affect the workings of nerve cells.

The study, published in the Journal of the American Geriatrics Society, included 2140 Mexican-American adults age 65 and older who were periodically given standard tests of mental function over 7 years.

At the outset, the men and women were screened for impairments in their corrected vision; for the test of near vision, they were asked to read numbers from a card while wearing their glasses or contact lenses.

Overall, 14 percent of study participants had impaired near-range vision, while 7 percent had problems with both near and distance vision. On average, the researchers found, these adults showed a quicker rate of decline on mental functioning tests over the next 7 years compared with their peers.

There was no association, however, between mental decline and impairments in either distance vision or hearing.

For reasons that are unclear, Mexican Americans seem to have a higher rate of age-related cognitive impairment than non-Hispanic older Americans. If poor vision is one factor, it will be particularly important to identify and treat the underlying causes of visual impairment in Mexican-American adults, according to Reyes-Ortiz and his colleagues.

It is not clear, the researchers note, whether treatments for low vision could have slowed the mental decline seen in some adults.

Still, Reyes-Ortiz said the findings point to the importance of routine eye care for older adults, who are at increased risk of vision-robbing eye diseases such as Glaucoma , cataract and Age-related macular degeneration. Depending on the disorder, treatment could involve a stronger lens prescription, vision aids such as a magnifying lens, medication or surgery.

“We want to try to correct the deficits early,” Reyes-Ortiz said.

But visual acuity is not the only factor in maintaining mental acuity. Reyes-Ortiz advised that older adults try to take up mentally engaging activities such as reading, painting and solving crossword puzzles.

SOURCE: Journal of the American Geriatrics Society, April 2005.