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Prediabetes defined by HbA1c may lead to worse prognosis

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March 13, 2018

Adults with prediabetes defined by HbA1c levels were more likely to have an increased risk for cardiovascular disease or all-cause mortality compared with adults with prediabetes defined by fasting plasma glucose or 2-hour plasma glucose, study data show.

Dorte Vistisen, MSc, PhD, senior research and team leader at the Steno Diabetes Center Copenhagen in Denmark, and colleagues evaluated data from the Whitehall II study on 5,427 adults aged 50 to 79 years without diabetes who were followed for a median of 11.5 years to compare the risks for CVD and all-cause mortality in subgroups of prediabetes defined by FPG, 2-hour plasma glucose or HbA1c.

Prediabetes was defined using WHO/International Expert Committee (IEC) criteria (FPG, 6.1-6.9 mmol/L and/or HbA1c, 6% to 6.4%) and American Diabetes Association criteria (FPG, 5.6-6.9 mmol/L and/or HbA1c, 5.7% to 6.4%). Additional measures of 2-hour plasma glucose were used to define prediabetes in a subset of 4,730 participants.

Overall, 7.4% of participants had prediabetes using WHO/IEC FPG criteria (mean age, 61.8 years; 85.6% men; 90.6% white), 5.3% by WHO/IEC HbA1c criteria (mean age, 65.5 years; 67.3% men; 80.1% white), 26.1% using ADA FPG criteria (mean age, 61.1 years; 83.9% men; 94.5% white) and 17.3% using ADA HbA1c criteria (mean age, 64.8 years; 66.8% men; 83.4% white).

During follow-up, 21.3% of participants with prediabetes defined by WHO/IEC criteria developed CVD or died compared with 18.5% of participants with prediabetes defined by the ADA criteria. The incident rates were 54% higher in participants with prediabetes defined by the WHO/IEC criteria and 37% higher in participants with prediabetes defined by the ADA criteria compared with participants with normoglycemia.

The rate of events was higher in participants with prediabetes defined by the WHO/IEC FPG criteria (19.4 per 1,000 person-years) compared with those with prediabetes defined by ADA FPG criteria (16.5 per 1,000 person-years); after full adjustment, incidence rates were the same level as those of participants with normoglycemia. The event rate was higher in participants with prediabetes defined by the WHO/IEC HbA1c criteria (29.5 per 1,000 person-years) compared with those with prediabetes defined by ADA HbA1c criteria (26 per 1,000 person-years). In the subset of participants with prediabetes defined by 2-hour plasma glucose, the event rate was 44% higher compared with participants with normoglycemia. However, after full adjustment for previous CVD, smoking, total cholesterol, HDL cholesterol, systolic blood pressure and use of antihypertensive treatment, the differences in incidence rates became nonsignificant.

“People with prediabetes are at increased risk of developing CVD or die prematurely. However, the amount of risk depends on how prediabetes is defined,” Vistisen told Endocrine Today. “Among this study population aged 50 to 80 years, prediabetes defined by HbA1c was associated with a higher risk of CVD and premature death than prediabetes defined by fasting glucose or 2-hour glucose following an OGTT. However, in general, the excess risk among people with prediabetes is mainly explained by the clustering of other cardiometabolic risk factors associated with hyperglycemia.”

“[Future] research should focus on evaluating the joint effect of prediabetes with other easily measured CV risk factors on predicting overall risk of CVD and mortality,” she said. – by Amber Cox

For more information:

Dorte Vistisen, MSc, PhD, can be reached at dorte.vistisen@regionh.dk.

Disclosures: Vistisen reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.