Normal-Tension Glaucoma Associated With Cognitive Impairment

By Lisa Rapaport

April 01, 2021

(Reuters Health) - Older adults with normal-tension glaucoma are more likely to develop cognitive impairment than counterparts with high-tension glaucoma, a new study suggests.

Researchers examined data from the Australian and New Zealand Registry of Advanced Glaucoma, randomly selecting 248 patients 65 years and older who had normal-tension glaucoma and were matched by age and sex with 349 controls with high-tension glaucoma.

A subset of patients with normal-tension glaucoma (n=144) or high-tension glaucoma (n=146) completed cognitive screenings using the Telephone Version of the Montreal Cognitive Assessment (T-MoCA).

Cognitive impairment was significantly more common among normal-tension glaucoma patients (odds ratio 2.2), researchers report in the British Journal of Ophthalmology.

There may be some shared genetic features between normal tension glaucoma and dementia, said lead study author Dr. Sean Mullany of Flinders University in Adelaide, Australia.

"We know that rare forms of frontotemporal dementia can result from mutations in two of the same genes that cause severe early-onset normal-tension glaucoma, so it's reasonable to think that there may be some more prevalent shared genetic features," Dr. Mullany said by email. "However, we don't fully understand the shared genetic landscape of glaucoma and dementia."

The absolute risk of cognitive impairment was relatively low, Dr. Mullany noted. A total of 21 (14.8%) patients with normal-tension glaucoma and 8 patients (5.4%) with high-tension glaucoma had cognitive impairment, based on a cutoff T-MoCA score of less than 11 out of 22.

The analysis did account for cardiovascular risk factors strongly associated with dementia, including stroke, smoking, hypertension, and type 2 diabetes.

"We suspect that much of this possible association may be the culmination of various systemic disease risk factors such as hypertension and hyperlipidemia, which are known to be associated dementia but remain to be understood in glaucoma," Dr. Mullany said.

It's possible that the cumulative effects of such risk factors may themselves be toxic to the eye, resulting in an eye that is more vulnerable to glaucomatous change, Dr. Mullany added.

However, one limitation of the study is that it didn't adjust for some potential confounders such as socioeconomic status, the researchers note. In addition, more than half of the cohort selected to participate in cognitive screening declined to do so.

Even so, the results add to the evidence suggesting there is a connection between normal-tension glaucoma and cognitive impairment, said Dr. Curt Ekstrom, a senior researcher at the Institution of Neuroscience at Uppsala University in Sweden.

"I believe that common risk factors can explain a possible association between normal-tension glaucoma and Alzheimer´s disease," Dr. Ekstrom, who wasn't involved in the study, said by email. "Ischemic heart disease is related to both normal-tension glaucoma and Alzheimer's disease."

SOURCE: British Journal of Ophthalmology, online March 29, 2021.