Incidence of dementia associated with cataract surgery

Cataract surgery was linked to a nearly 30% reduced risk of dementia in the elderly, a prospective study showed.

Among 3,000 patients with cataracts, cataract removal was associated with a significantly reduced risk of dementia compared to people without surgery (HR 0.71, 95% CI 0.62-0, 83, P<0.001), reported Cecilia Lee, MD, MS, of the University of Washington in Seattle, and co-authors of JAMA Internal Medicine.

The association between cataract surgery and dementia remained significant after controlling for several confounding factors and taking into account the bias of healthy patients. The decreased risk persisted for at least a decade after surgery, the researchers said.

“Sensory loss, such as vision loss from untreated cataracts, is of interest to the research community as a potentially modifiable risk factor for dementia,” Lee said. MedPage today.

“Cataract disease affects many older people and cataract surgery is a widely available intervention,” she added. “To date, there are very few known measures, other than certain lifestyle factors such as diet and exercise, that are considered preventive against dementia.”

Researchers followed 3,038 people diagnosed with cataracts or glaucoma as part of the Adult Changes in Thought program (ACT), a Seattle-based study by Kaiser Permanente Washington. Participants were dementia free at the time of enrollment and had not had cataract surgery prior to enrollment. The mean age of the group was 74.4; overall, 59% were female and 91% were white. Data was collected from 1994 to September 2018.

Participants in the ACT cohort were assessed every 2 years with the Cognitive Abilities Screening Instrument (CASI). CASI scores range from 0 to 100, and participants with scores below 85 underwent further diagnostic testing.

About 45% of the group (1,382 people) had cataract surgery during the study. The mean follow-up was 7.8 years. A total of 853 people developed dementia, mainly Alzheimer’s disease (709 cases).

Unlike cataract removal, researchers did not find a lower risk of dementia in people who had glaucoma surgery (HR 1.08, 95% CI 0.75-1.56, P= 0.68).

Cataract removal was more strongly associated with reduced risk of dementia in the first 5 years after cataract surgery (HR 0.68, 95% CI 0.56-0.81, P<0.001) compared to later years (HR 0.76, 95% CI 0.63-0.92, P= 0.02). Among several variables, including additional education, race, smoking history and gender, the only covariate more protective than cataract surgery did not carry a APOE4 allele.

“One possible mechanism by which cataract surgery could reduce the risk of dementia or Alzheimer’s disease is by enabling better sensory delivery to the retina and therefore improving brain stimuli,” observed Lee. “Additionally, patients may be able to more fully engage in the world with improved vision, which may have a protective effect against the development of dementia.”

“Another potential explanation for the association between cataract surgery and decreased risk of dementia concerns how cataracts affect the type and quality of light that reaches the retina,” added Lee.

Cataracts cause the lens to develop a yellow tint that blocks blue light. Inherently photosensitive retinal ganglion cells in the retina are “extremely sensitive to blue light stimuli and are known to regulate circadian cycles,” Lee said.

“The degeneration and impaired function of these cells has been shown to be associated with cognition and Alzheimer’s disease,” she said. “Because cataracts affect the overall quality of light that reaches the retina, including blue light, cataract surgery can reactivate these cells in a way that protects against cognitive decline. “

The study has several limitations, the researchers acknowledged. Reverse causation was a possibility; people with early cognitive problems may be less aware of vision problems, which can delay cataract surgery. Only a participant’s first cataract surgery was evaluated, and it was not known whether subsequent surgeries influenced the risk of dementia. In addition, most of the participants were white and the results may not apply to other groups.

Last updated on December 06, 2021