Long-Term Diabetes Triples Stroke Risk

Allison Shelley

March 08, 2012

March 8, 2012 — Having diabetes for a decade or more dramatically increases the risk for ischemic stroke, report researchers.

The new study, published online March 1 in the journal Stroke, found diabetes increases risk 3% each year and triples at 10 years.

Dr. Mitchell Elkind

"We were not surprised to see an increased risk," senior investigator Mitchell Elkind, MD, from Columbia University Medical Center in New York City, told Medscape Medical News. "But we were taken aback by how high the risk was."

Using data from the Northern Manhattan Study, investigators looked at 3298 multi-ethnic participants. They found that 22% had diabetes at baseline and another 10% went on to develop the disease over the course of the study. There were 244 ischemic strokes.

"Our study provides evidence that the risk of ischemic stroke increased continuously with duration of diabetes mellitus," the authors explain. This was after controlling for other factors such as age, smoking history, physical activity, history of heart disease, blood pressure, and cholesterol.

"The increase is not as much during the second half of the first decade," they noted, "but it increases steeply as the disease enters its second decade."

Duration of Diabetes and Ischemic Stroke Risk

Diabetes (Years) Hazard Ratio 95% Confidence Interval
0 to 5 1.7 1.1 - 2.7
5 to 10 1.8 1.1 - 3.0
>10 3.2 2.4 - 4.5

Among the nearly 26 million Americans with diabetes, more than half are younger than age 65 years, according to the American Diabetes Association.

"We used to think of type 2 diabetes as a disease people get when they are older, after a lifetime of poor dietary habits," Dr. Elkind said. "But the age at diagnosis is getting younger and younger because of the obesity problem among young people."

The researchers pointed out that diabetes was determined by self-report in this study. "It's possible we missed some cases," Dr. Elkind added during an interview. An estimated one third of diabetes cases may be undiagnosed. It has also been found that true onset of diabetes may be 4 to 7 years earlier than clinical diagnosis.

As the population ages and the elderly live longer, more and more people will live with longer duration of disease, the authors note. "It is important to better understand the dynamics between diabetes, time, and stroke, and to emphasize the importance of interventions to prevent early diabetes. Minimizing the number of years a patient has diabetes would help combat the increase in stroke risk with each year of the disease."

Some of the reasons for increased stroke risk may include an association between longer diabetes duration and thicker plaque in neck arteries and the higher prevalence of hypertension, accelerated vascular complications, and clotting abnormalities.

Northern Manhattan Study

Asked by Medscape Medical News to comment on the findings, Philip Gorelick, MD, from the Hauenstein Neuroscience Institute, in Grand Rapids, Michigan, said the Northern Manhattan Stroke Study has provided a wealth of information about risk factors for stroke over the years. One of the important risk factors for stroke is diabetes.

"In this publication, the authors have shown little incremental value of using diabetes as a time-dependent variable when compared to baseline assessment of diabetes as a risk for stroke. With duration of diabetes, however, the risk of stroke does increase. This is a key take-home message for clinicians as intensification of risk factor management may be very important amongst those who have had diabetes for a longer time period as their relative risk of having a stroke becomes higher with time."

Although tight control of blood glucose may not reduce stroke risk, he pointed out, associated problems such as high blood pressure and dyslipidemia are prime targets for patients with diabetes.

"Young people should be educated about diabetes and how to prevent it," Dr. Elkind added. "Eating a healthy diet, remaining physically active, and avoiding smoking are important."

The Northern Manhattan Study is funded by the National Institute of Neurological Disorders and Stroke. The investigators have disclosed no relevant financial relationships.

Stroke. Published online ahead of print March 1, 2012. Abstract


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