Glaucoma is an eye disease that damages the optic nerve, the eye-brain connection for the transfer of visual information. The disease is typically associated with abnormally high eye pressure, but can also occur with eye pressure inside the normal range of 10 mmHg (millimeters of mercury) to 21 mmHg. While previous studies of associations between glaucoma and Alzheimer’s disease (AD) have shown inconsistent results, a large, population-based study in Taiwan offers proof of a link between normal-tension glaucoma (NTG) and elevated risk of AD.*

What the researchers did

At AAO 2022, the American Academy of Ophthalmology’s 126th annual meeting, researchers explained that they examined the medical records of 75,585 people from Taiwan’s National Health Insurance Database over 12 years. Of these, 15,317 people had NTG, and 61,268 people had no glaucoma.

Both groups were matched by age and gender for more robust results. For added study strength, the researchers adjusted for diabetes, coronary artery disease, stroke, high blood pressure, and high cholesterol.

What they found

After adjusting for confounding factors, the researchers found a 52% greater likelihood of people with NTG developing AD than people without glaucoma. In addition:

• Those with the highest incidence of AD were older, female, and/or had a stroke history.
• Eye drops did not protect against AD in people with NTG.

What it means

Lead researcher Yu-Yen Chen, M.D., Ph.D. of Taiwan’s Taichung Veterans General Hospital said that in the interest of public health, policymakers should enact AD screening for at-risk people with NTG, along with substantial and comprehensive care.

AD won’t happen to everyone with glaucoma, but the study highlights a possible link through a process called neurodegeneration in which nerve cells gradually die off. In people with glaucoma, retinal ganglion cells in the optic nerve are affected; in AD, brain cells involved in cognition and memory are impacted.

‘Encouraging’ for future research

The researchers hope that treatments can be developed with further examination of the similarities and differences between the two conditions. In a separate interview, co-author Preeti Subramanian, Ph.D., BrightFocus Foundation’s director of scientific programs in vision science, said the study is “encouraging” for movement in that direction. Subramanian noted that future research should assess the extent of NTG and vision loss in participants, and how that relates to AD, which wasn’t examined in the current study.

Co-author Diane Bovemkamp, Ph.D., BrightFocus’ vice president of scientific affairs, explained that implementing AD screening for at-risk individuals with NTG could involve guidelines for doctors that alert them to AD risk and help them manage underlying conditions. 

*American Academy of Ophthalmology. (2022, September 30). New Study Shows People with Glaucoma are at Significant Risk of Alzheimer’s Disease. https://www.aao.org/newsroom/news-releases/detail/people-with-glaucoma-are-at-risk-for-alzheimers