1-hour glucose value may predict mortality risk

A 1-hour glucose value above 155 mg/dL (≥8.6 mmol/L) predicted mortality even when the 2-hour glucose value was below 140 mg/dL (<7.8 mmol/L), according to a recent study.

Researchers followed 2,138 patients over 33 years for all-cause mortality and used fasting and post-oral glucose tolerance test values to determine glycemic status at baseline. Patients who had diabetes at baseline were excluded. The 4 categories of glycemic status were as follows.

• Group A: 1-hour glucose value ≤155 mg/dL (≤8.6 mmol/L) and 2-hour glucose value <140 mg/dL (<7.8 mmol/L)
• Group B: 1-hour glucose value >155 mg/dL (>8.6 mmol/L) and 2-hour glucose value <140 mg/dL (<7.8 mmol/L)
• Group C: 1-hour glucose value ≤155 mg/dL (≤8.6 mmol/L) and 2-hour glucose value 140 to 199 mg/dL (7.8 to 11.0 mmol/L) (impaired glucose tolerance)
• Group D: 1-hour glucose value >155 mg/dL (>8.6 mmol/L) and 2-hour glucose value 140 to 199 mg/d (7.8 to 11.0 mmol/L) (impaired glucose tolerance)

Patients in group A were the youngest and had the lowest body mass index, and patients in group D were an average of 5 years older and had the highest body mass index. Of the study cohort, 1,112 were in group A, 449 were in group B, 83 were in group C, and 301 were in group D. The study results were published online April 15 by Diabetic Medicine.

Fifty-one percent of the study cohort had died by August 2013. Mortality rates were highest in group D (73.8%), followed by group C (67.5%), group B (57.9%), and group A (41.6%). The researchers controlled for sex, age, smoking, body mass index, and systolic and diastolic blood pressure and found that patients with a normal 2-hour glucose value (<140 mg/dL or <7.8 mmol/L) had a 28% increased risk for death compared with group A if they also had a 1-hour glucose value >155 mg/dL (>8.6 mmol/L). Groups B, C, and D had gradually increased risks for mortality versus group A (hazard ratios, 1.28, 1.60, and 1.76, respectively).

The authors noted that the oral glucose tolerance test was performed only once, at baseline, and that no temporal relationship was seen between abnormal 1-hour and 2-hour glucose values. In addition, they pointed out that the 100-g glucose load, which is no longer used in practice, was still in use when the study was started. However, they wrote, their findings indicate that use of the 1-hour glucose level versus only the 2-hour glucose level might avoid underestimating the severity of glycemic disorders, mortality, and cardiovascular risk factors. “Identifying those at an early point in the evolution to worsening dysglycaemia may, therefore, have the greatest benefit of preserving [beta]-cell function and preventing or reversing a decline towards diabetes and increased mortality,” the authors concluded. They called for further prospective studies to be done on the issue.