Siblings of people with glaucoma have a significantly greater risk of developing the eye condition and should be screened for it, concludes a study in the current issue of the British Journal of Ophthalmology.
Researchers monitored 271 siblings of 156 people with glaucoma for more than a decade and found that 11.8 percent of the siblings were diagnosed with definite glaucoma and 5.5 percent were diagnosed with suspected glaucoma.
The study concluded that siblings of people with glaucoma have a 20 percent lifetime chance of developing the disease, a rate that's about four times the risk of the general population. This link between siblings could be the result of similar genes and/or shared environment, said the researchers, from University Hospital Nottingham in England.
They noted that the average time between initial glaucoma assessment and the last visit to an optician was just over a year. This suggests that opticians are not always able to detect glaucoma in this group of people who are at increased risk for the condition, the researchers said.
"We therefore suggest that formal screening resources should be targeted at this high-risk group, and that a screening program should actively recall siblings every two years even if the initial screening results are negative," the study authors wrote.
Glaucoma is a group of diseases that can damage the eye's optic nerve and result in vision loss, even blindness.
More information
The Glaucoma Foundation has more about glaucoma.
In a carefully controlled study, the arteries of healthy volunteers exposed to diesel exhaust lost part of their ability to expand, while their blood became more likely to clot.
The bad news about the cardiovascular harm that polluted air can inflict doesn't end there.
In a study reported in the Dec. 21 issue of the Journal of the American Medical Association, New York University researchers found that mice exposed to air as polluted as what floats around New York City showed that the effects can be particularly damaging, especially when coupled with a high-fat diet.
The human study answers a question scientists have posed for years, one expert noted.
"People have wondered for a long time whether diesels were harmful, and if so, how," said Dr. Russell V. Luepker, a professor of epidemiology at the University of Minnesota, and a spokesman for the American Heart Association. "This study is a building block. It shows that when you look hard for mechanisms, you find them."
Luepker was not involved in the study, which was conducted by Scottish researchers at the University of Edinburgh and published in the Dec. 20 issue of Circulation.
The research relied on a specially built "exposure chamber" at the university's Center for Cardiovascular Science. In two one-hour sessions, 30 healthy young men were exposed either to filtered air or to exhaust from an idling diesel engine. The researchers then injected vasodilators -- drugs that cause the arteries to expand -- and took blood samples to measure clotting levels.
Response to the vasodilators was reduced significantly after the diesel exposure, and levels of an enzyme that helps keep clots from forming were reduced, the researchers reported.
The findings have potentially important implications for the U.S. Environmental Protection Agency, which is currently sponsoring a voluntary program to outfit diesel-powered vehicles with devices that trap fine particles in exhaust fumes.
"Diesel exhaust consists of a complex mixture of particles and gases," said study author Dr. Nick Mills, a clinical research fellow at the Edinburgh center. "Before we can advocate the widespread use of particle traps in diesel engines, we need to verify that combustion-derived particles are the responsible component."
A number of real-world studies have linked diesel fume exposure to heart attacks and other cardiovascular problems, Mills noted.
"However, observational studies cannot prove causality," he said. "In human exposure studies, we can control for all potential confounding factors and assess the direct effect of particulates on the cardiovascular system. Our findings provide further support for the observational studies and a plausible mechanism to explain association between particles and acute cardiovascular events."
It's not clear whether the findings apply to gasoline-powered engines, Mills said, because their emissions are very different from those of diesel-powered engines. In particular, diesel exhaust generates 100 times more pollutant particles, he said.
Because the study was so carefully controlled, Luepker labeled the results "interesting initial data." But he added that "the controlled study in the laboratory is not totally dissimilar to what people out on the street can be exposed to."
"If this study were done in mice, I would say, 'very interesting,' " Luepker said. "A study done in healthy humans gets my attention more."
In the mouse study from JAMA, the scientists found that mice breathing polluted air developed far more plaque than those breathing filtered air. Rodents that were exposed to polluted air and a high-fat diet had arteries that were 41.5 percent obstructed with plaque, while the mice exposed to a high-fat diet and filtered air only experienced 26.2 percent blockage in their arteries.
The mice on normal diets also revealed differences in plaque levels, with the mice exposed to polluted air showing 19.2 percent blockage while those exposed to filtered air showing only 13.2 percent blockage. All the mice were genetically prone to develop heart disease.
More information
For more on diesel pollution, head to the U.S. Environmental Protection Agency.
