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Elevated 1-hour post-load glucose reliable predictor of prediabetes risk
An elevated 1-hour postload glucose level during an oral glucose tolerance test may better predict prediabetes risk, even when the 2-hour level falls within a normal glucose tolerance range, according to recent study findings.
In an analysis of a large Israeli population assessed for all-cause mortality over more than 30 years, researchers found that an elevated 2-hour glucose level indicated increased mortality risk, independent of the 1-hour level.
“Other studies suggest that the 1-hour glucose level above 155 mg/dL is a better predictor of progression to diabetes than the 2-hour level,” Michael Bergman, MD, FACP, clinical professor of medicine at NYU School of Medicine and director of the NYU Diabetes Prevention Program, told Endocrine Today. “[Our] present findings, in conjunction with the [other] observations, suggest that individuals at high risk for developing diabetes could be identified earlier by measuring the 1-hour postload glucose level.”
Michael Bergman
Bergman and colleagues analyzed data from 2,138 adults without diabetes at baseline from the Israel Study of Glucose Intolerance, Obesity and Hypertension, a study including a random population sample from the Israel Central Population Registry stratified by age, sex and ethnic origin. Patients completed a 2-hour, 100 g OGTT between 1979 and 1984 (baseline); the cohort was followed for all-cause mortality over a 33-year period.
Researchers categorized the cohort by baseline 1- and 2-hour glucose levels: group A (1 hour ≤ 155 mg/dL and 2 hours < 140 mg/dL; n = 1,112); group B (1 hour > 155 mg/dL and 2 hours < 140 mg/dL; n = 449); group C (1 hour ≤ 155 mg/dL and 2 hours 140-199 mg/dL; n = 83); group D (1 hour > 155 mg/dL and 2 hours 140-199 mg/dL; n = 301).
By August 2013, 51% of the study cohort had died. Researchers found group D had the worst prognosis (73.8% mortality), followed by groups C (67.5%), B (57.9%) and A (41.6%).
“In these non-[impaired glucose tolerance] groups, the absolute mortality difference between an elevated and a normal 1-hour glucose approximated 16%, whereas in the IGT groups (group C vs. D), the absolute mortality difference between the 1-hour groups only approximated,” the researchers wrote.
Patients with a 2-hour glucose level less than 140 mg/dL but an elevated 1-hour glucose had a 28% increased mortality risk vs. patients with non-elevated 1- and 2-hour glucose levels, according to researchers. With group A as a reference, researchers found a gradual increased hazard for mortality by study group (HR = 1.28, 1.6 and 1.76, for groups B, C and D, respectively).
“We have previously found that beta-cell function appears to be better preserved in those with a 1-hour level below 155 mg/dL, and declines when the 1-hour value exceeds this value and deteriorates incrementally with IGT and [type 2 diabetes],” Bergman said. “Therefore, a prevention study to determine if therapeutic lifestyle intervention in those with a 1-hour level above 155 mg/dL without IGT is warranted.” – by Regina Schaffer
For more information:
Michael Bergman, MD, FACP, can be reached at the NYU School of Medicine, Division of Endocrinology, Diabetes and Metabolism, Schwartz East- Suite 5E, 530 First Ave., New York, NY 10016; email: Michael.bergman@nyumc.org.
Disclosure: The researchers report no relevant financial disclosures.
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Recently, increasing evidence has suggested that a plasma glucose concentration at least 155 mg/dL at 1 hour during an oral glucose tolerance test (OGTT) can identify individuals at increased risk for future development for type 2 diabetes among those who have normal glucose tolerance (2-hour glucose during OGTT less than 140/mg/dL). Remarkably, subjects with normal glucose tolerance and a 1-hour post-load plasma glucose at least 155 mg/dL are characterized by a cluster of metabolic and cardiovascular abnormalities, including insulin resistance and reduced beta-cell function, and elevated inflammation markers, and have signs of subclinical organ damage, including carotid artery thickness, vascular stiffness, hepatic steatosis, diminished glomerular filtration rate, and left ventricular hypertrophy — all independent predictors of subsequent cardiovascular events. In this study, the authors show that individuals with a 1-hour glucose value at least 155 mg/dL are at increased risk for mortality for any cause, as compared with normal glucose tolerance individuals with a 1-hour glucose value below 155 mg/dL, after adjusting for confounders. The results of this study are similar to those observed in a previous Finnish study and support the notion that hyperglycemia at 1-hour during an OGTT may be a useful tool to identify a subset of individuals conceivably harboring a high risk for developing type 2 diabetes and adverse clinical outcomes.