Impaired fasting glucose: how low should it go?

Area of Science:

• Endocrinology
• Metabolic Disorders
• Epidemiology

Background:

• Impaired fasting glucose (IFG) is a recently defined stage of abnormal carbohydrate metabolism.
• The current glucose limits for IFG (fasting plasma glucose [FPG] 6.1–6.9 mmol/l) lack strong supporting evidence.
• The existence of a clear threshold for IFG remains uncertain.

Purpose of the Study:

• To evaluate if 6.1 mmol/l represents a distinct cutoff for future diabetes risk.
• To determine if 6.1 mmol/l is a threshold for elevated cardiovascular risk factors.
• To explore the utility of lower FPG limits for defining IFG.

Main Methods:

• A population-based survey was conducted in Mauritius in 1987 with a 5-year follow-up.
• Oral glucose tolerance tests and cardiovascular risk factor measurements were performed at both time points.
• Data from 4,721 non-diabetic individuals at baseline and 3,542 at follow-up were analyzed.

Main Results:

• Cardiovascular risk factors (blood pressure, lipids, obesity) increased linearly with FPG at baseline, showing no threshold effect.
• Individuals with baseline FPG ≥ 6.1 mmol/l had a significantly higher risk of developing hypertension at follow-up (P<0.001).
• The risk of developing diabetes increased with higher baseline FPG, with no clear threshold observed near 6.1 mmol/l.

Conclusions:

• Cardiovascular risk and future diabetes risk escalate continuously with increasing FPG, indicating no specific threshold for IFG definition.
• Defining IFG with a lower limit around 5.8 mmol/l would categorize individuals more similarly to those with impaired glucose tolerance regarding prevalence and diabetes risk.