Re-Defining Future Stroke Risk among Pre-Diabetics

Millions of pre-diabetic Americans may be at increased risk of future stroke, say researchers at the University of California, San Diego School of Medicine in a new meta-analysis of epidemiological studies, but the precise degree of that threat is confounded by differing medical definitions and factors that remain unknown or unmeasured.

“The immediate implication of our findings is that people with pre-diabetes should be aware they are at increased risk of stroke, and that this condition is frequently associated with one or more major risk factors for cardiovascular disease,” said Bruce Ovbiagele, MD, a professor of neurosciences at UC San Diego School of Medicine and the study’s senior author. “Beyond that, there’s a great need to further refine our understanding of that risk and how it’s measured.”

Writing in the June 8 online edition of the British Medical Journal, Ovbiagele and an international team of colleagues reviewed 15 qualifying prospective cohort studies that looked at the association between pre-diabetes and stroke risk. The studies, published between 2004 and 2011, involved 760,925 participants.

Pre-diabetes occurs when blood glucose levels are consistently higher than normal, but not yet high enough to be diagnosed as diabetes. The condition is widespread in the United States: An estimated 35 percent of American adults – approximately 79 million people – are believed to be pre-diabetic, and thus at greater risk of developing full-blown type-2 diabetes, which afflicts roughly 26 million Americans. Diabetes is the seventh leading cause of death in the U.S., and a major risk factor for heart disease and stroke, the first and fourth leading causes of death.

People with pre-diabetes typically have the same risk factors for cardiovascular disease as people with type 2 diabetes – specifically, high blood pressure, high cholesterol levels and obesity – but the condition’s effect on future stroke risk has not been established.

What is prediabetes? A: Prediabetes is when a person's blood glucose levels are higher than normal but not high enough to be type 2 diabetes. People with prediabetes are more likely to develop type 2 diabetes and may have some problems from diabetes already.

Q: If I have prediabetes, will I definitely develop type 2 diabetes?
A: No. Research shows that you can lower your risk for type 2 diabetes by 58% by:

- Losing 7% of your body weight (or 15 pounds if you weigh 200 pounds)
- Exercising moderately (such as brisk walking) 30 minutes a day, five days a week

Don't worry if you can't get to your ideal body weight. Losing just 10 to 15 pounds can make a huge difference. For some people with prediabetes, early treatment can actually return blood glucose levels to the normal range.

Ovbiagele and colleagues found that an association between future stroke risk and pre-diabetes depended upon the definition of the latter. To determine whether someone has pre-diabetes, blood glucose levels are typically measured after a 12-hour fast. According to the 1997 American Diabetes Association (ADA), a normal fasting glucose measurement ranges between 70.2 to 100 milligrams per deciliter (mg/dL). A level between 100 and 126 mg/dL is considered pre-diabetic. A level of 126 mg/dL or above is diabetic.