The eye disease, glaucoma, is the single biggest cause of blindness in the United States, affecting about 1.9 per cent of people aged 40 or over. A recent study shows a link between excessive caffeine and the disease – but the report’s conclusions need to be carefully interpreted.
What is Glaucoma?
Glaucoma is a disease in which fluid passing through a spongy meshwork behind the eye, slows down. Because it moves slower, the fluid builds up and pressure inside the eye increases causing damage to the optic nerve.
About the Research
The research led by the Icahn School of Medicine at Mount Sinai shows that there is an interaction of diet and genetics with glaucoma. The study which is published in the June print issue of Ophthalmology suggests those who have a hereditary pattern of glaucoma should limit caffeine intake.
The research is available publicly, and attached below – the report is highly technical, but the summary is worth reading:
The report summary has two conclusions:
- Habitual caffeine consumption was associated weakly with lower Interocular Pressure (IOP), and the association between caffeine consumption and glaucoma was null
- Those with a strong genetic predisposition to glaucoma were disproportionately affected by caffeine intake. i.e. caffeine makes those with a predisposition to glaucoma, worse.
Reading a little more in the conclusions, we noted that for the most adversely affected – those with hereditary patterns of the disease, the actual amount of caffeine consumed in the study was 321mg a day, and this resulted in the patient being 3.9 times more likely to develop glaucoma.
For reference, a 30g shot of espresso may contain 64 mg of caffeine, depending on the type of beans, so it seems I’m probably safe sticking to my two double espresso shots in the morning.
It was unclear whether there was a linear relationship between consumption and the likelihood of developing symptoms. For example, if I was in a high-risk group and consumed 160mg a day of caffeine, would I be two times more likely to develop issues?
Some ethnic groups will be even more at risk based on historical susceptibility to the disease – see the chart below.