THURSDAY, March 1, 2012 (HealthDay News) -- People who've had type 2 diabetes for more than 10 years are three times more likely to have a stroke than people without diabetes, new research suggests.
"The longer people had diabetes, the more likely they were to have a stroke. The risk went up pretty dramatically, to up to a threefold risk for people who've had diabetes more than 10 years," said senior study author Dr. Mitchell Elkind, an associate professor of neurology and associate chair for clinical research and training at Columbia University Medical Center in New York City.
Elkind said the findings point to an even greater need for people to "do everything they can to prevent type 2 diabetes. Get regular exercise, eat a healthy diet, see your physician regularly and avoid smoking."
Results of the study are published in the April issue of Stroke.
This study only looked at the most common type of stroke, called ischemic stroke, which occurs when one or more blood vessels in the brain become blocked by a blood clot, according to the National Stroke Association. When this happens, the area of the brain that's no longer receiving blood and oxygen becomes damaged.
Almost 3,300 people from New York City participated in the study. The average age of the participants was 69, and nearly two-thirds were women. Twenty-one percent were white, 24 percent were black and 52 percent were Hispanic. Forty-four percent of the volunteers had Medicaid or no insurance.
When the study began, 22 percent of the participants had diabetes. The average duration of diabetes for those who had it at the start of the study was 17 years.
Ten percent of those who didn't have diabetes at the start of the study developed the disease during the nine years of follow-up. The average duration of diabetes for this group was 4.5 years.
During the study period, there were 244 ischemic strokes.
The risk of ischemic stroke increased by 3 percent for every year a person had type 2 diabetes, the researchers found.
Someone who's had diabetes less than five years has a 70 percent increased risk of ischemic stroke, while someone who's had diabetes for five to 10 years has an 80 percent increased risk compared to someone without diabetes. A duration of diabetes longer than 10 years was linked to more than a threefold increase in the risk of ischemic stroke, according to the study.
The study authors suggest several reasons why people with type 2 diabetes could have an increased risk of stroke. One is that people with diabetes may have more plaque build-up in their arteries, particularly the carotid artery that supplies blood to the brain. Another reason is that high blood pressure, a known risk factor for stroke, is more prevalent in people with diabetes.
However, while the study uncovered an association between type 2 diabetes and stroke, it did not prove a cause-and-effect relationship.
Elkind said that the study wasn't able to discern whether better blood sugar control would reduce the risk of stroke. Nor did the study look at whether blood pressure and cholesterol management made a difference in the risk of stroke, though Elkind said he suspects they would make a difference.
"Controlling cholesterol and high blood pressure are very important," he said.
Commenting on the study, Dr. Vivian Fonseca, president of medicine and science at the American Diabetes Association, said, "If you have diabetes, you do have an increased risk of stroke, and the risk goes up as the diabetes duration increases."
Fonseca said this study emphasizes the importance of good blood pressure and cholesterol control for people with diabetes. And, while more evidence is needed on good blood sugar control and the risk of stroke, keeping your blood sugar in check can help improve your health in other ways.
Elkind added that "diet and exercise are really powerful ways to help prevent stroke."
Learn more about stroke and diabetes from the American Diabetes Association.