It's possible that alcohol may increase glaucoma risk, study shows. Photo: Edward Howell on Unsplash.

Previous epidemiological studies have reported cross-sectional associations between alcohol use and higher IOP, and IOP is a known risk factor for open-angle glaucoma (OAG). Because of this, researchers recently conducted a systematic review and meta-analysis evaluating the existing evidence for the association of alcohol use with IOP and OAG.

Three databases were independently screened and assessed. All case-control, cross-sectional and cohort studies reporting a quantitative effect estimate and 95% confidence interval for the association between alcohol use and either IOP or OAG were included. The evidence for the associations with both IOP and OAG were qualitatively summarized, and effect estimates for the association with OAG were pooled using random effects meta-analysis.

A total of 34 studies were included, with 10 reporting that habitual alcohol use is associated with higher IOP and prevalence of ocular hypertension (IOP >21mm Hg), although absolute effect sizes were small. Of the 26 studies that tested for an association with OAG, 11 met inclusion criteria for meta-analysis.

The team noted that if alcohol is not consumed at a frequency regular enough to result in sustained ocular hypotension or in the hours preceding IOP measurement, this physiological effect may not be apparent. The direct short-term effects of alcohol may be outweighed by potential indirect or long-term IOP-raising effects as well, they added.

The exact pathophysiological mechanisms in how alcohol is implicated in OAG risk are not clear, but it is known that chronic alcohol use can lead to significant peripheral neuropathy. The proposed underlying mechanisms may play a similar role in glaucomatous optic neuropathy, including oxidative stress leading to free radical damage to nerves, activation of the sympatho-adrenal and hypothalamo-pituitary-adrenal axes and nutritional deficiencies (especially thiamine).

Additionally, alcohol may indirectly influence OAG risk through its association with a number of neurodegenerative and cardiovascular diseases, and it is possible that residual confounding effects may be responsible. The association between alcohol use and IOP may further contribute to OAG risk.

“This finding should be interpreted with caution, however, given the significant methodological heterogeneity and risk of bias present in the underlying evidence base, as well as the small absolute effect size and borderline statistical significance,” the authors concluded. “Further study is needed to better define and quantify these associations, but alcohol consumption should be considered a potential modifiable risk factor for the development of glaucoma. In particular, future research is needed to better define the dose-dependent associations of alcohol with various glaucoma-related outcomes and traits, as well as the gene-alcohol interactions underpinning these associations.”