Having Diabetes for a Decade Triples Stroke Risk

Having diabetes for a decade or more dramatically increases the risk for ischemic stroke 3% each year and triples at 10 years....

Senior investigator Mitchell Elkind, MD, from Columbia University Medical Center in New York, stated that, "We were not surprised to see an increased risk, 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.

The authors explained, "Our study provides evidence that the risk of ischemic stroke increased continuously with duration of diabetes mellitus." "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. Dr. Elkind said, "We used to think of type 2 diabetes as a disease people get when they are older, after a lifetime of poor dietary habits, 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.