New research indicates that both insulin-dependent (type 1) diabetes and non-insulin-dependent (type 2) diabetes is associated with substantially increased risks of stroke overall, and most subtypes of stroke.

Strokes occur when the blood flow to the brain stops, causing brain cells to begin dying within minutes. There are two types of strokes. The most frequent kind is called ischemic stroke and is triggered by a blood clot that blocks a blood vessel in the brain. Hemorrhagic stroke is triggered when a blood vessel breaks and bleeds into the brain.

“Our study indicates that women with both type 1 and type 2 diabetes mellitus are at increased risk for ischemic stroke, and type 1 diabetes mellitus is associated with excess risk of Hemorrhagic stroke,” Dr. Mohsen Janghorbani, lead author of the new research, told Reuters Health.

“The risk of stroke is also associated with duration of type 2 diabetes,” Janghorbani of Isfahan University of Medical Sciences in Iran added.

The findings are based on 3,463 strokes documented in more than 116,000 women in the Nurses’ Health Study, Janghorbani and colleagues note in the journal Diabetes Care.

The relative risk of stroke was 4.7-fold higher in women with type 1 diabetes and 1.7-fold higher in those with type 2 diabetes, compared to women without diabetes.

The risk of ischemic stroke was 6.3-fold higher in type 1 diabetes and 2.3-fold higher in type 2 diabetes.

Type 1 diabetes was significantly associated with the risk of Hemorrhagic stroke (relative risk, 3.8). There was no increased risk of Hemorrhagic stroke in type 2 diabetics.

The researchers note that controlling for high blood pressure “modestly attenuated these relationships” but that other variables had little impact.

“With worldwide increasing prevalence of diabetes mellitus, the population attributable risk of stroke will likely increase,” said Janghorbani.

The results also highlight the importance of controlling all known stroke risk factors, especially high blood pressure, in patients with diabetes mellitus, the researcher added.

SOURCE: Diabetes Care July 2007.