AHA.15: Patients with diabetes have increased long-term risk of stroke following CABG

The long-term risk of stroke after patients underwent CABG was significantly higher in patients with type 1 or type 2 diabetes compared with those who did not have diabetes, according to an analysis from Swedish researchers.

The risk of death in combination with stroke was twice as high in patients with type 1 diabetes compared with patients with no diabetes, although the risk of death was similar in patients with type 2 diabetes and those without diabetes.

Lead researcher Thomas Nystrom, MD, PhD, of Karolinska Institutet in Stockholm, Sweden, and colleagues presented their results on Nov. 9 in a poster session at the American Heart Association (AHA) Scientific Sessions. The findings were simultaneously published online in the Journal of the American Heart Association.

“Conclusions regarding the association between type of diabetes and subcategories of stroke must be drawn with caution,” the researchers wrote. “In addition, the point estimate suggested that the association between type 1 diabetes and stroke was stronger than the association between type 2 diabetes and stroke. However, even in this large study population, there were few events among patients with type 1 diabetes that led to confidence intervals being wide and overlapping.”

The researchers analyzed all patients who underwent primary CABG in Sweden from 2000 through 2011 and were included in the SWEDEHEART register. They excluded patients with a history of stroke, prior cardiac surgery or who underwent emergency surgery within 24 hours of the decision to operate as well as those who had a stroke or died within 30 days of surgery.

They defined type 1 diabetes as “onset of diabetes before the age of 30 years and treatment with insulin only” and type 2 diabetes as “diabetes treated with diet or oral hypoglycemic agents alone, or age of ≥40 years at onset of diabetes and treatment with insulin alone or in combination with oral hypoglycemic agents.”

Of the 53,820 patients in the study, 1 percent had type 1 diabetes, 19 percent had type 2 diabetes and 80 percent had no diabetes. Patients with type 1 diabetes were approximately 10 years younger than the other patients and were more often female, more likely to have chronic kidney disease or end-stage renal disease and more likely to have peripheral vascular disease.

After a mean follow-up period of 7.4 years, 8 percent of patients had a stroke, including 7.3 percent of patients with type 1 diabetes, 7.7 percent of patients with no diabetes and 9.1 percent of patients with type 2 diabetes.

In age-adjusted and multivariable analyses, the risk for stroke was 59 percent higher in patients with type 1 diabetes and 32 percent higher in patients with type 2 diabetes compared with patients without diabetes.

In addition, after a mean follow-up period of 7.8 years, 22 percent of patients died, including 22 percent of patients with type 1 diabetes, 22 percent of patients with no diabetes and 21 percent of patients with type 2 diabetes.

The researchers noted this was an observational study, so they may not have been able to adjust for unmeasured risk factors in their statistical models. They also mentioned that the results were not generalizable to patients undergoing PCI or those who had prior cardiac surgery or prior stroke.