Stroke: Diabetes duration ups risk of ischemic stroke
Does duration of diabetes impact a patient's risk for ischemic stroke? Yes, said researchers from Columbia University when they found that the risk of ischemic stroke increases 3 percent each year and triples when diabetes is present for 10 years or more. The study results were published March 1 in Stroke.

“Diabetes increases stroke risk, but whether diabetes status immediately before stroke improves prediction and whether duration is important are less clear,” wrote Chirantan Banerjee, MBBS, MPH, of Columbia University in New York City, and colleagues.

And to better understand whether there is a link between ischemic stroke risk and diabetes, Banerjee and colleagues analyzed patient data from 3,298 stroke-free patients included in the Northern Manhattan Study to determine incidence of diabetes. The authors looked at whether patients had diabetes at baseline and reported the patient's age at diagnosis.

Patients included in the study had a mean age of 69 years; 62.8 percent were female. Additionally, 52.3 percent were Hispanic, 20.9 percent were non-Hispanic white and 24.3 percent were non-Hispanic black.

At baseline, 574 patients self-reported diabetes and 142 patients had a fasting blood glucose level of less than 126 mg/dL. Therefore, it was reported that 716 total patients had diabetes at baseline. Of the 2,582 patients who did not have diabetes at baseline, 338 patients reported new-onset of diabetes during a mean of nine years of follow-up.

The researchers reported 244 ischemic strokes. Additionally, the authors said that baseline diabetes was linked to the risk of stroke. Even when the new onset of diabetes was taken into consideration, diabetes was still found to be associated with a risk of ischemic stroke.

As for the duration of diabetes, the researchers reported that mean duration among people who self-reported diabetes at baseline was 17.3 years. And, among the 338 patients with diabetes who were diagnosed during follow-up, the mean duration of diabetes was recorded to be 4.5 years. As the years of diabetes increased, ischemic stroke risk increased 3 percent.

“Our findings suggest that there is marginal incremental value to including further assessments of diabetes during follow-up in analyses of its effect on stroke risk,” the authors wrote. The researchers said that an implication of the research could be the fact that potential cost savings could be avoided through less lengthy interviews and assessments of risk factors during follow-up. However, the authors said it remains unknown whether these findings are transferable to other risk factors and CV outcomes.

The authors included several explanations as to why there was an absence of additional information from follow-up assessments in the analysis including:

  • The CV risk factor burden carried by patients at baseline could be high enough that the development of diabetes during follow-up did not confer added information;
  • Patients with newly diagnosed diabetes could be more compliant with treatments, which can be beneficial for primary stroke prevention;
  • The median duration for follow-up for those with diabetes at baseline was 13.7 years, but only 4.2 years for patients who developed diabetes after baseline. This may not be sufficient to manifest cerebrovascular events; and
  • Self-reported and lab results were used to identify diabetes at baseline.
For patients diagnosed with diabetes for 10 years or more, ischemic stroke risk was three times that of those without diabetes.

“Our study provides evidence that the risk of ischemic stroke increased continuously with duration of diabetes mellitus,” the researchers wrote. “The increase is not as much during the second half of the first decade, but it increases steeply as the disease enters its second decade. This must, however, be interpreted keeping in mind that true onset of diabetes may be four to seven years earlier than clinical diagnosis.”

The authors said that one explanation that could explain the linkage between diabetes and ischemic stroke found in the study could be the association between diabetes duration and atherosclerotic lesions, which includes intimal medial thickness and thin cap fibroatheromas.

Because of the aging baby boomer population, the authors said that it will be important to understand the dynamics between diabetes duration and stroke, as patients are now living longer.

“As more people have development of diabetes earlier and live longer, this relationship assumes public health importance and warrants steps to institute long-standing and sustainable lifestyle changes for primary prevention and appropriate long-term management after diagnosis,” the authors summed.