Lower Cut-Off Point of Blood Glucose May Define Prediabetes

Doctors define prediabetes as impaired fasting glucose with a higher than normal blood sugar levels after a period of fasting, impaired glucose tolerance with a higher than normal blood sugar levels after eating, or raised glycosylated hemoglobin levels.

Results of studies on the association between prediabetes and risk of cardiovascular disease and all-cause mortality are also inconsistent. Furthermore, whether raised glycosylated hemoglobin levels for defining prediabetes is useful for predicting future cardiovascular disease is unclear.

Scientists affiliated with the Affiliated Hospital at Shunde, (Southern Medical University, Foshan, China) analyzed the results of 53 studies involving over 1.6 million individuals to shed more light on associations between different definitions of prediabetes and the risk of cardiovascular disease, coronary heart disease, stroke, and all-cause mortality.

Prediabetes was defined as impaired fasting glucose according to the criteria of the American Diabetes Association (ADA, Arlington County, VA, USA; IFG-ADA; fasting glucose 5.6-6.9 mmol/L), the World Health Organization expert group (WHO, Geneva, Switzerland; IFG-WHO; fasting glucose 6.1-6.9 mmol/L), impaired glucose tolerance (two hour plasma glucose concentration 7.8-11.0 mmol/L during an oral glucose tolerance test), or raised hemoglobin A1c (HbA1c) of 39-47 mmol/mol (5.7-6.4%) according to ADA criteria or 42-47 mmol/mol (6.0-6.4%).

The scientists found that prediabetes, defined as impaired fasting glucose or impaired glucose tolerance, was associated with an increased risk of cardiovascular disease and all-cause mortality. The risk increased in people with a fasting glucose concentration as low as 5.6 mmol/L (100.8 mg/dL), which was the lower cut-off point according to ADA criteria. Raised HbA1c levels to 39-47 mmol/mol or 42-47 mmol/mol were both associated with an increased risk of composite cardiovascular disease and coronary heart disease but not with an increased risk of stroke and all-cause mortality.

The authors concluded that prediabetes, defined as impaired glucose tolerance, impaired fasting glucose, or raised HbA1c, was associated with an increased risk of cardiovascular disease. The health risk might be increased in people with a fasting glucose concentration as low as 5.6 mmol/L or HbA1c of 39 mmol/mol. The study was published on November 23, 2016, in the journal BMJ.

Related Links:
Southern Medical University
American Diabetes Association
World Health Organization