Compared to infrequent drinkers in this study, regular drinkers had both a higher IOP and thinner macular ganglion cell-inner plexiform layer. Photo: Stanislav Ivanitskiy on Unsplash.

While drinking can provide some health benefits in moderation, one new study to appear in Ophthalmology Glaucoma outlines that this is not the case when considering glaucoma and its related traits. The study in question, recently published online ahead of print, sought to clarify any association between alcohol consumption and glaucoma as well as assess whether a genetic predisposition to glaucoma modified the association in any way.

To carry out this question, researchers conducted a cross-sectional study using data from the UK Biobank. From this information, they performed Mendelian randomization (MR) experiments to probe causal effects of the substance.

A total of 173,407 glaucoma patients were included in the retrospective study. Of those, data for intraocular pressure (IOP) was included for a total of 109,097 participants and the researchers had access to 46,236 macular OCT scans. From there, the team categorized participants by self-reported drinking behavior and estimates of alcohol intake were derived.

Alcohol Use Categories in this Study never drinkers (no past or present use) infrequent drinkers (special occasions only) regular drinkers (1-3x/month or greater) former drinkers (no current use but have previously)

Researchers compared the categories of alcohol consumption (never, infrequent, regular and former drinkers), then assessed a dose-response effect for the regular drinker category. Then, researchers assessed if any associations were modified by a multi-trait polygenic risk score for glaucoma.

What they found was that regular drinkers displayed both a higher IOP and thinner macular ganglion cell-inner plexiform layer (mGCIPL) thickness when compared to infrequent drinkers. For those regular drinkers, their intake of alcohol was associated adversely with all outcomes dose-dependently. The MR analyses were able to conclude a causal relationship with the mGCIPL thickness.

Those with a stronger genetic susceptibility to developing glaucoma had much stronger alcohol-IOP associations. Alarmingly, researchers found that alcohol intake observed with adverse effects was at a lower level than the current UK and US guidelines.

Following that, there was no observed protective association with any outcome, which is interesting, giving that there is evidence of neuroprotective properties of polyphenols, found in high concentration in red wine, which also contains anti-inflammatory and antioxidant compounds. The researchers propose this might be due to the detrimental effects of alcohol on glaucoma outweighing any of its potential benefits, even at low intake.

The researchers do weigh in on the potential biological mechanisms underpinning the association. One theory involves the association representing a combination of causative factors linked to chronic alcohol usage, including biomechanical and physiological differences as well as neurodegenerative, cardiovascular and endocrine disorders. In this way, it might not be a single mechanism contributing to the observed association.

The authors do point out in their paper that “while we cannot infer causality definitively, these results will be of interest to people with, or at risk of, glaucoma and their advising physicians.” As these findings might help physicians with those at risk of developing glaucoma, the authors highlight that “the presence of an underlying causal association may have important clinical and public implications and may lead to targeted lifestyle recommendations for glaucoma.”

Stuart KV, Luben RN, Warwick AN, et al. The association of alcohol consumption with glaucoma and related traits: findings from the UK Biobank. Ophthalmol Glauc. 2022. [Epub ahead of print].