According to a new study, drinking more than three cups of coffee per day has been shown to correlate with an increased risk of developing glaucoma, which can lead to vision loss or blindness.
"While caffeinated coffee has several health benefits," lead researcher Jae Hee Kang told Health magazine, "drinking three or more cups of caffeinated coffee was found to be associated with increased risk of developing exfoliation glaucoma, particularly among those with a family history of glaucoma."
While coffee has for some time been known to be problematic for glaucoma sufferers due to the fact that it can increase pressure within the eyeball, Kang asserts that the hot brown drug can be linked to a specific type of the vision-destroying malady: exfoliation glaucoma. This syndrome occurs when material is rubbed off both the eye's iris and lens, which then clogs up the eyeball's fluid-draining system, leading to heightened inter-ocular pressure (IOP), which increases the risk of glaucoma.
Kang and her team's study, published in Investigative Ophthalmology & Visual Science, surveyed data from two studies, one with 78,977 women and another with 41,202 men. Its findings are not conclusive in a cause-and-effect sense, however – correlation is not causation, as we all know from our college classes – and the statistical significance of her findings is weak.
That said, her team did discover that those subjects who drank three or more cups of caffeinated coffee per day did have a higher incidence of exfoliation glaucoma than those who either abstained or were more moderate in their intake of a cup of joe – or three.
Despite the less than iron-clad results, the study concludes that "We observed a positive association between heavier coffee consumption with risk of [exfoliation glaucoma or exfoliation glaucoma suspect] in this large prospective study."
One medical professional is unconvinced. Referring to the studies from which Kang and her coauthors obtained the data, ophthalmology professor Alfred Sommer of Johns Hopkins University told Health, "These two studies have yielded literally thousands of articles, almost all of little value."
According to Sommer, the studies are missing the information researchers need to take into account the many variables that might influence conclusions to be drawn from them.
"To make matters worse," he added, "the conclusions in [Kang's] study don't even reach statistical significance."
Sommer's argument is a strong one – if you're looking for certainty. If, however, you've got a family history of glaucoma and you're not particularly lucky in life, you might think of making that third latte a decaf. ®