In a nationally representative sample of older adults in the United States, Stanford researchers found a strong relationship between visual impairment and cognitive decline, as recently reported in JAMA Ophthalmology.
The research team investigated this association in elderly populations by analyzing two large U.S. population data sets -- over 30,000 respondents from the National Health and Aging Trends Study and almost 3,000 respondents from the National Health and Nutrition Examination Study -- which both included measurements of cognitive and vision function.
"After adjusting for hearing impairment, physical limitations, patient demographics, socioeconomic status and other clinical comorbidities, we found an over two-fold increase in odds of cognitive impairment among patients with poor vision," said Suzann Pershing, MD, assistant professor of ophthalmology at Stanford and chief of ophthalmology for the VA Palo Alto Health Care System. "These results are highly relevant to an aging U.S. population."
Previous studies have shown that vision impairment and dementia are conditions of aging, and their prevalence is increasing as our populations become older. However, the Stanford authors noted that their results are observational and do not establish a causative relationship.
The complexity of the relationship between vision and cognition was discussed in a related commentary by Jennifer Evans, PhD, an assistant professor of epidemiology at the London School of Hygiene and Tropical Medicine. She stated that this association could arise owing to problems with measuring vision and cognitive impairment tests in this population. "People with vision impairment may find it more difficult to complete the cognitive impairment tests and... people with cognitive impairment may struggle with visual acuity tests," she wrote.
Assuming the association between vision and cognitive impairment holds, Evans also raised questions relevant for patient care, such as: Which impairment developed first? Would successful intervention for visual impairment reduce the risk of cognitive impairment? Is sensory impairment an early marker of decline?
Pershing said she plans to follow up on the study:
I am drawn to better understand the interplay between neurosensory vision, hearing impairment and cognitive function, since these are likely synergistic and bidirectional in their detrimental effects. For instance, vision impairment may accelerate cognitive decline and cognitive decline may lead to worsening ability to perform visual tasks. Ultimately, we aim to better identify impairment and deliver treatments to optimize all components of patients' health.
Previously: Long-distance eye-brain connections, partial vision restored for first time ever in a mammal and Imaging study shows genetics and environment affect different parts of the brain
Image by Les Black