Can regular caffeine consumption be detrimental to eyesight?

Heavy caffeine intake appears to contribute to higher intraocular pressure (IOP) and glaucoma prevalence, but only among individuals with the highest genetic susceptibility to elevated IOP, as shown in a study.

“This study suggests that a large panel of IOP genetic biomarkers could modify the relation between caffeine dietary intake and risk of glaucoma,” the investigators said.

The analysis used data from the UK Biobank and included 121,374 participants (mean age, 56.8 years; 53.8 percent female). Their average baseline IOP was 16.0 mm Hg. Mean coffee intake was 1.9 cups/day, and mean tea intake was 3.1 cups/day.

In a subset of 77,906 participants who completed up to five web-based 24-hour-recall food frequency questionnaires, total mean caffeine intake ranged from 8.9 mg/d for noncoffee drinkers to 135.3 mg/d for heavy coffee consumers (>1 cup/day), and from 2.9 mg/d for nontea drinkers to 114.0 mg/d for heavy tea consumers (>3 cups/day).

Overall, greater caffeine intake was weakly associated with lower IOP, with intake levels of ≥232 versus <87 mg/day correlating with a 0.10-mm Hg lower IOP (p=0.01). Meanwhile, the associations of coffee, tea, and total caffeine consumption with glaucoma were null (9,286 patients and 189,763 controls). [Ophthalmology 2020;doi:10.1016/j.ophtha.2020.12.009]

Restricting analyses to participants with genetic data (n=117,458), the investigators constructed a polygenic risk score (PRS) based from 111 genetic variants associated with IOP elevation. They found that the PRS modified the association between caffeine intake and IOP.

Participants in the highest IOP PRS quartile who consumed >480 mg versus <80 mg of caffeine per day had a 0.35-mm Hg higher IOP (p=0.01). Likewise, participants in the highest IOP PRS quartile with caffeine intake of ≥321 mg/day had a 3.90-fold higher glaucoma prevalence compared with those in the lowest IOP PRS quartile who consumed no caffeine (p=0.0003).

Mendelian randomization analysis based on eight genetic variants associated with coffee intake did not support a causal effect of coffee drinking on IOP (p>0.1).

“It is interesting to speculate about the biology underlying a possible interaction between IOP PRS and dietary caffeine intake in modifying the risk of higher IOP and glaucoma. It is possible that [individuals] with high IOP PRS have a lower reserve to withstand the challenges of intermittent yet frequent acute elevations of IOP caused by caffeine consumption,” the investigators noted.

To date, there is no approved genetic testing to identify the subset of patients predisposed to higher IOP and glaucoma. As such, the investigators called for additional research to confirm these observed gene-diet interactions and to establish “whether specific genetic markers are modifying the propensity to higher IOP and glaucoma or whether it is a nonspecific critical number of any IOP markers that modify disease risk.

“If confirmed, our data suggest that approaches to precision nutrition that incorporate genomic data may be needed to make recommendations regarding caffeine consumption and glaucoma risk,” they added.