MONDAY, Feb. 16, 2004 (HealthDayNews) -- Elderly people whose arteries that feed blood to the brain are blocked face a higher risk not only of stroke, but an inability to think clearly, a new study says.
These large vessels on either side of the neck, called carotid arteries, can become blocked over time as plaque builds up on the artery walls, narrowing the vessels and restricting blood flow. As blood flow in the vessel is slowed, clots can occur. These clots, when pushed though the artery, can block smaller arteries in the brain, causing a stroke.
"But blockages in the carotid arteries are also associated with having trouble with thinking," says lead researcher Dr. S. Claiborne Johnston, an associate professor of neurology and epidemiology at the University of California at San Francisco.
Johnston's research team looked at 4,006 men and women aged 65 and older who were included in the Cardiovascular Health Study. None of these people had had a stroke or a transient ischemic attack (TIA). A TIA is a small stroke that usually lasts for a few minutes, leaving no apparent damage.
The researchers used ultrasound to determine the condition of each patient's left carotid artery.
They also had the subjects take a test, called the Modified Mini-Mental State Examination, which evaluated their cognitive status. The test was repeated annually for up to five years, according to their report in the Feb. 17 issue of the Annals of Internal Medicine.
His team found that, when compared to people with normal carotid arteries, the 32 volunteers who had a severely narrowed neck vessel had significant cognitive decline.
"We don't know why this happens," Johnston says. "The presumption is either that it causes very tiny strokes that are below our ability to detect, or that it happens due to reduced blood flow to the brain."
Johnston believes a series of small, undetectable strokes are the cause. "These patients are already at risk for a major stroke, and this suggests that they are also at risk for having trouble with thinking," he adds.
In addition, Johnston says the decline in thinking caused by these tiny strokes can lead to dementia.
These findings suggest that more people should undergo an operation to open their carotid arteries, Johnston says. The procedure, called a carotid endarterectomy, is usually reserved for patients who have severely narrowed arteries or who have had a stroke or TIA.
Carotid disease may be causing other problems besides stroke and TIA, and doctors and patients need to be aware of that and look for treatments to see if the risk can be reduced without causing other problems, Johnston says.
"The problem right now is that we don't have the data which tells us whether the surgery would eliminate the risk of cognitive decline. We also don't know if the surgery could cause little strokes that cause cognitive decline," Johnston says.
Dr. Henry J.M. Barnett, professor emeritus of medicine at the University of Western Ontario, says that while this study adds knowledge, it fails to show how this cognitive decline affects patients' daily lives.
In his editorial in the same journal issue, he also notes that collateral circulation, which creates new blood vessels to compensate for small vessels that are blocked, may prevent both stroke and cognitive decline.
Barnett goes on to say the reason for cognitive decline seen in some patients might be due to other factors, such as a brain tumor, vitamin B12 deficiency, or disease of the small arteries in the brain.
Moreover, he is afraid these findings may promote carotid endarterectomies solely to prevent cognitive decline. A carotid endarterectomy is a high-risk operation that carries with it the risk of stroke and death, he says.
Barnett also points out that only a very skilled surgeon should perform this procedure. "It would be a pity to see an untoward rush toward doing a whole lot more carotid endarterectomies, using cognitive decline as the reason for operating on an otherwise asymptomatic artery," he says.