One-Hour Glucose Concentration May Help Predict Type 2 Diabetes

A 1-hour plasma glucose concentration higher than 155 mg/dL measured during an oral glucose tolerance test, plus the presence of the metabolic syndrome, strongly predicts future risk for type 2 diabetes in subjects with normal glucose tolerance, according to the results of a large population-based epidemiologic study.

Reliable models for identifying people at risk for the development of type 2 diabetes are essential, because lifestyle changes and pharmacologic interventions can reduce the likelihood that the disease will develop, according to the study, which was published in Diabetes Care.

The researchers used a classification tree model that can stratify risk for nondiabetics with risk factors such as obesity, dyslipidemia, and hypertension based on their 1-hour glucose concentration. The model was previously demonstrated to be a better predictor for future type 2 diabetes than fasting plasma glucose or the 2-hour plasma glucose concentration, according to Dr. Muhammad A. Abdul-Ghani and colleagues in the divisions of diabetes and epidemiology, University of Texas Health Science Center at San Antonio.

They tested the model in a study population of 1,611 adults from the population-based San Antonio Heart Study. All patients had oral glucose tolerance tests at baseline and again at follow-up, 7–8 years later.

None had diabetes at baseline, but 90 had impaired fasting glucose (IFG), 220 had impaired glucose tolerance (IGT), and 51 of the 220 with IGT also had IFG and were designated as having combined glucose intolerance (CGI).

During the 7- to 8-year follow-up period, the conversion rate to diabetes was 5% for those who had normal glucose tolerance at baseline, 26.1% for those with IFG, 30.9% for those with IGT, and 82.3% for those with CGI.

Patients were partitioned in the classification tree according to whether their 1-hour plasma glucose concentration was above or below 155 mg/dL, and stratified as being at low risk for future diabetes, with an annual risk below 0.5%; at intermediate risk, with an annual risk of 1–2%; or at high risk, with an annual risk greater than 4%.

Analysis revealed that in patients with normal glucose tolerance, the annual risk for future type 2 diabetes was significantly higher, at 2.2%, in those whose 1-hour plasma glucose concentration was higher than 155 mg/dL, than for those with concentrations below this level, whose risk was 0.39% per year.

For those with normal glucose tolerance whose glucose concentration was higher than 155 mg/dL and who also had metabolic syndrome, the annual risk was very high, at 4.3%.

Their odds ratio for developing diabetes, at 15.2, is double that of patients with IGT whose 1-hour plasma glucose is below 155 mg/dL. “This group of high-risk individuals [with normal glucose tolerance] could benefit from an intervention program employing diet, exercise, and pharmacotherapy (metformin) to reduce future risk for diabetes,” Dr. Abdul-Ghani and colleagues wrote (Diabetes Care 2008;31:1650–5).

The investigators also noted that their model is better at predicting risk than is the American Diabetes Association criteria of IGT or IFG. “About 17% of normal glucose-tolerant subjects, who have immediate and high risk for future type 2 diabetes and who were identified with the 1-h plasma glucose plus metabolic syndrome, would have been missed with the American Diabetes Association criteria alone,” they wrote.

A 1-hour plasma glucose concentration higher than 155 mg/dL measured during an oral glucose tolerance test, plus the presence of the metabolic syndrome, strongly predicts future risk for type 2 diabetes in subjects with normal glucose tolerance, according to the results of a large population-based epidemiologic study.

Reliable models for identifying people at risk for the development of type 2 diabetes are essential, because lifestyle changes and pharmacologic interventions can reduce the likelihood that the disease will develop, according to the study, which was published in Diabetes Care.

The researchers used a classification tree model that can stratify risk for nondiabetics with risk factors such as obesity, dyslipidemia, and hypertension based on their 1-hour glucose concentration. The model was previously demonstrated to be a better predictor for future type 2 diabetes than fasting plasma glucose or the 2-hour plasma glucose concentration, according to Dr. Muhammad A. Abdul-Ghani and colleagues in the divisions of diabetes and epidemiology, University of Texas Health Science Center at San Antonio.

They tested the model in a study population of 1,611 adults from the population-based San Antonio Heart Study. All patients had oral glucose tolerance tests at baseline and again at follow-up, 7–8 years later.

None had diabetes at baseline, but 90 had impaired fasting glucose (IFG), 220 had impaired glucose tolerance (IGT), and 51 of the 220 with IGT also had IFG and were designated as having combined glucose intolerance (CGI).

During the 7- to 8-year follow-up period, the conversion rate to diabetes was 5% for those who had normal glucose tolerance at baseline, 26.1% for those with IFG, 30.9% for those with IGT, and 82.3% for those with CGI.

Patients were partitioned in the classification tree according to whether their 1-hour plasma glucose concentration was above or below 155 mg/dL, and stratified as being at low risk for future diabetes, with an annual risk below 0.5%; at intermediate risk, with an annual risk of 1–2%; or at high risk, with an annual risk greater than 4%.

Analysis revealed that in patients with normal glucose tolerance, the annual risk for future type 2 diabetes was significantly higher, at 2.2%, in those whose 1-hour plasma glucose concentration was higher than 155 mg/dL, than for those with concentrations below this level, whose risk was 0.39% per year.

For those with normal glucose tolerance whose glucose concentration was higher than 155 mg/dL and who also had metabolic syndrome, the annual risk was very high, at 4.3%.

Their odds ratio for developing diabetes, at 15.2, is double that of patients with IGT whose 1-hour plasma glucose is below 155 mg/dL. “This group of high-risk individuals [with normal glucose tolerance] could benefit from an intervention program employing diet, exercise, and pharmacotherapy (metformin) to reduce future risk for diabetes,” Dr. Abdul-Ghani and colleagues wrote (Diabetes Care 2008;31:1650–5).

The investigators also noted that their model is better at predicting risk than is the American Diabetes Association criteria of IGT or IFG. “About 17% of normal glucose-tolerant subjects, who have immediate and high risk for future type 2 diabetes and who were identified with the 1-h plasma glucose plus metabolic syndrome, would have been missed with the American Diabetes Association criteria alone,” they wrote.

A 1-hour plasma glucose concentration higher than 155 mg/dL measured during an oral glucose tolerance test, plus the presence of the metabolic syndrome, strongly predicts future risk for type 2 diabetes in subjects with normal glucose tolerance, according to the results of a large population-based epidemiologic study.

Reliable models for identifying people at risk for the development of type 2 diabetes are essential, because lifestyle changes and pharmacologic interventions can reduce the likelihood that the disease will develop, according to the study, which was published in Diabetes Care.

The researchers used a classification tree model that can stratify risk for nondiabetics with risk factors such as obesity, dyslipidemia, and hypertension based on their 1-hour glucose concentration. The model was previously demonstrated to be a better predictor for future type 2 diabetes than fasting plasma glucose or the 2-hour plasma glucose concentration, according to Dr. Muhammad A. Abdul-Ghani and colleagues in the divisions of diabetes and epidemiology, University of Texas Health Science Center at San Antonio.

They tested the model in a study population of 1,611 adults from the population-based San Antonio Heart Study. All patients had oral glucose tolerance tests at baseline and again at follow-up, 7–8 years later.

None had diabetes at baseline, but 90 had impaired fasting glucose (IFG), 220 had impaired glucose tolerance (IGT), and 51 of the 220 with IGT also had IFG and were designated as having combined glucose intolerance (CGI).

During the 7- to 8-year follow-up period, the conversion rate to diabetes was 5% for those who had normal glucose tolerance at baseline, 26.1% for those with IFG, 30.9% for those with IGT, and 82.3% for those with CGI.

Patients were partitioned in the classification tree according to whether their 1-hour plasma glucose concentration was above or below 155 mg/dL, and stratified as being at low risk for future diabetes, with an annual risk below 0.5%; at intermediate risk, with an annual risk of 1–2%; or at high risk, with an annual risk greater than 4%.

Analysis revealed that in patients with normal glucose tolerance, the annual risk for future type 2 diabetes was significantly higher, at 2.2%, in those whose 1-hour plasma glucose concentration was higher than 155 mg/dL, than for those with concentrations below this level, whose risk was 0.39% per year.

For those with normal glucose tolerance whose glucose concentration was higher than 155 mg/dL and who also had metabolic syndrome, the annual risk was very high, at 4.3%.

Their odds ratio for developing diabetes, at 15.2, is double that of patients with IGT whose 1-hour plasma glucose is below 155 mg/dL. “This group of high-risk individuals [with normal glucose tolerance] could benefit from an intervention program employing diet, exercise, and pharmacotherapy (metformin) to reduce future risk for diabetes,” Dr. Abdul-Ghani and colleagues wrote (Diabetes Care 2008;31:1650–5).

The investigators also noted that their model is better at predicting risk than is the American Diabetes Association criteria of IGT or IFG. “About 17% of normal glucose-tolerant subjects, who have immediate and high risk for future type 2 diabetes and who were identified with the 1-h plasma glucose plus metabolic syndrome, would have been missed with the American Diabetes Association criteria alone,” they wrote.