Glaucoma raises risk of death in blacks: study

NEW YORK (Reuters Health) - Black people treated for glaucoma are at increased risk of dying from heart and vascular disease, particularly those treated with timolol maleate eye drops, according to data from the Barbados Eye Studies.

Similar associations have been observed in white populations, the investigators note, but whether timolol eye drops mediate the increased risk or is simply a marker for more advanced glaucoma is not clear.

"Glaucoma is one of the leading causes of visual impairment worldwide," Suh-Yuh Wu and colleagues note in the journal Archives of Ophthalmology. "The most common type, primary open-angle glaucoma, is especially prevalent in populations of African origin, in which it is the foremost cause of blindness."

In addition to higher rates of open-angle glaucoma, black populations also tend to have higher rates of death from chronic disease and high pressure within their eyes (ocular hypertension) relative to white populations.

In open-angle glaucoma, fluid cannot drain properly from the eyeball, leading to increased pressure within the eye and damage to the optic nerve. It may be treated with medication to lower pressure in the eye, and surgery may be performed to restore normal drainage.

Ms. Wu, at Stony Brook University in New York, and colleagues evaluated long-term mortality rates among 4092 subjects who had eye examinations between 1987 and 1992 as part of the Barbados Eye Studies. They note that more than 90 percent of Barbados citizens are black, life expectancy is high, and health care is free so access to care is not an issue in this cohort.

At the beginning of the study, 300 participants had glaucoma, including 141 who had been diagnosed and treated. After 9 years of follow-up, 764 (19 percent) of the participants had died.

Glaucoma was not associated with the risk of death overall. However, the risk of death from cardiovascular causes was 38 percent higher in people who had previously been diagnosed with or treated for open-angle glaucoma and 91 percent higher in those who had been treated with timolol eye drops.

Cardiovascular deaths were also 28 percent higher in those with ocular hypertension at the beginning of the study.

"One explanation for the excess mortality found in persons with previously diagnosed open-angle glaucoma could be their longer duration of disease compared with those with newly diagnosed disease," Wu and colleagues suggest.

"Another explanation for an increased mortality risk could be related to the open-angle glaucoma treatment received." Side effects or inappropriate use of beta-blockers and other medications used to treat glaucoma may harm the cardiovascular system and increase death risk, they also point out.

"The excess mortality associated with timolol maleate treatment ... warrants further investigation," the team concludes.

SOURCE: Archives of Ophthalmology, March 2008.