Image of Cecilia S Lee, M.D.; Image credit: University of Washington School of Medicine
Cecilia S Lee, M.D.; Image credit: University of Washington School of Medicine

Older adults who have had cataract surgery are nearly 30% less likely to develop dementia from any cause when compared with their peers who have not, a new study finds. What’s more, these patients also are less likely to develop Alzheimer’s specifically.

This lowered risk of dementia persisted for at least a decade after the surgery, the researchers reported. 

Investigators used data from 5,000 participants aged 65 years and older and adjusted the results for a number of possible confounding variables such as chronic disease. The study design makes the resulting evidence particularly strong, according to researcher Cecilia S Lee, M.D., of the University of Washington School of Medicine.

“This kind of evidence is as good as it gets in epidemiology,” Lee said. “This is really exciting because no other medical intervention has shown such a strong association with lessening dementia risk in older individuals.”

Participants were diagnosed with a cataract or glaucoma but did not have dementia when they initially volunteered for the study. They underwent cognitive screening with the Cognitive Abilities Screening Instrument every two years.

Past studies that have found a connection between cognitive impairment and declining sensory abilities, including sight and hearing. Cataracts result from a breakdown of proteins which cloud the lens of the eye. They develop slowly over time and are commonly found in older age. Cataract surgery removes the damaged lens and replaces it with an artificial one, improving vision. 

People who have had the surgery may be getting higher quality sensory input, which in turn has an effect on the brain, the researchers hypothesized. The ability to see blue light also may have something to do with this connection between cataract surgery and brain health, they added. 

“Some special cells in the retina are associated with cognition and regulate sleep cycles, and these cells respond well to blue light,” Lee said. “Cataracts specifically block blue light, and cataract surgery could reactivate those cells.” 

“These results are consistent with the notion that sensory input to the brain is important to brain health,” concluded co-author Eric B. Larson, M.D., of the Kaiser Permanente Washington Health Research Institute.

The UW School of Medicine has released a video further explaining the study results. 

Full findings were published in JAMA Internal Medicine.