According to a study published online in British Medical Journal (BMJ), individuals who are pre-diabetic may be at increased risk of stroke.

Almost all people who suffer from type 2 diabetes had pre-diabetes first. Pre-diabetes is characterized by higher than normal blood glucose levels. In the UK, it is estimated that 7 million people are affected by the condition and 79 million people in the United States.

Like people with type 2 diabetes, individuals with pre-diabetes are at risk for high cholesterol, obesity and hypertension. However, researchers do not know how pre-diabetes effects the risk of future stroke.

In order to examine the association between risk of stroke and pre-diabetes, researchers from the University of California analyzed results of 15 studies involving 760,925 participants. The team took into account other cardiovascular risk factors, such as lifestyle and weight.

According to the researchers the association seems to depend on the definition of pre-diabetes. Pre-diabetes is usually characterized as impaired fasting glucose (raised blood glucose levels after a 12-hour fast). A range of 70.2 to 100 mg/dl is normal, while a level of 100 to 126 mg/dl is considered a sign of pre-diabetes.

The team discovered that pre-diabetes based on the 1997 American Diabetes Association (ADA) definition of 110 to 125 mg/dl carried a 21% increased risk of stroke.

However, pre-diabetes was redefined by the ADA in 2003 as an impaired fasting glucose of 100 to 125mg/dL. The researchers found that in studies using this definition, there was no increased risk of stroke.

According to the team, these findings may indicate that the risk of stroke only starts to increase at or above a fasting glucose level of 110 mg/dL.

The researchers note that the quality of evidence was variable and that there may be other factors that explain these results.

They conclude that individuals were at a “modestly higher risk of future stroke” if their fasting glucose was 110 to 125mg/dL/ However, those with the 2003 ADA’s definition (100 to 125mg/dL), are not at increased risk.

Individuals with pre-diabetes “should be aware that they are at increased risk of future stroke,” say the researchers, and that these people should adopt a healthy lifestyle and manage their weight in order to reduce this risk.

In an associated report, Dr. Jonathan Treadwell, from the ECRI Institute in Philadelphia, notes that is impossible to determine the exact size of the association due to unmeasured factors, such as hypertension, age, and obesity. Furthermore, he states that the study is “too simple” to categorize whether an individual has pre-diabetes, diabetes and not diabetes. However, Treadwell commends Lee’s study for thinking “outside of the box of what meta-analysis can achieve,” and notes that “clinical question must drive the research methods.”

Written By Grace Rattue