High-Normal Blood Sugar Could Signal Diabetes Risk
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Young men with fasting plasma glucose levels in the high-normal range appear to be at increased risk for type 2 diabetes, especially if they are on the heavy side and have high serum triglyceride levels.
That’s the finding of researchers here who studied more than 13,000 apparently healthy young men in the Israeli defense forces. The investigators found that so-called “normal” test values may actually predict type 2 diabetes. The results of their study were published in today’s issue of the New England Journal of Medicine.
“Higher fasting plasma glucose levels within the normoglycemic range constitute an independent risk factor for type 2 diabetes among young men, and such levels may help, along with body-mass index and triglyceride levels, to identify apparently healthy men at increased risk for diabetes,” wrote Amir Tirosh, M.D., Ph.D., from the Israeli Defense Forces Medical Corps and colleagues at various Israeli institutions.
According to the American Diabetes Association, fasting plasma glucose (FPG) levels below 100 mg/dL (5.55 mmol/L) are considered to be normal, whereas levels between 100 mg/dL and 109 mg/dL signal impairment.
But readings at the upper end of the normal limit - just below the 100 mg/dL threshold - might signal risk for future diabetes, Dr. Tirosh and colleagues reasoned, and could serve as a risk marker.
“In young adults, the absolute incidence of type 2 diabetes is low, but a marked surge in diabetes-associated morbidity has recently been reported,” they wrote. “Better and earlier identification of young adults at risk for the development of diabetes may be warranted, given the success of interventions aimed at delaying the onset of diabetes among high-risk groups.”
To see how things stood with glucose among young Israeli adults, they drew on data from the Metabolic, Lifestyle and Nutrition Assessment in Young Adults study, which tracks all Israeli service personnel older than 25. Participants fill out a detailed demographic, nutrition, lifestyle and medical questionnaire, and have blood samples drawn after a 14-hour fast.
The study included data on 13,163 apparently healthy men ages 26 to 45 years, all of whom had FPG levels of less than 100 mg/dL at baseline.
During a total 74,309 person-years of follow-up (from 1992 through 2004), there were 208 incident cases of type 2 diabetes. The investigators found that the age-adjusted hazard ratios for type 2 diabetes increased with every quintile of FPG levels. Men in the top quintile had a three-fold higher risk for diabetes compared with the lowest quintile (HR 3.05, 95% confidence interval, 1.78 to 5.18, p <0.001).
Using a multivariate model adjusted for age, family history of diabetes, body-mass index, physical-activity level, smoking status, and serum triglyceride levels, the authors found in men with FPG of 87 mg/dL (4.83 mmol/L) or higher there was a progressively greater risk for type 2 diabetes as the FPG values rose, compared with men who had an FPG of less than 81 mg/dL (4.5 mmol/L), p = <0.001.
Another significant risk factor for type 2 diabetes was serum triglyceride levels of 150 mg per deciliter (1.69 mmol/L) or higher, combined with fasting plasma glucose levels of 91 to 99 mg/dL (5.05 to 5.50 mmol/L). The hazard ratio for this combination was 8.23 (95% CI, 3.6 to 19.0) for diabetes, compared with men with a combined triglyceride level of less than 150 mg/dL and FPG and less than 86 mg/dL (4.77 mmol /L).
A similarly large risk was detected in men with a BMI of 30 or more and an FPG level of 91 to 99 mg/dL. The hazard ratio for this infelicitous pairing was 8.29 (95% CI, 3.8 to 17.8), compared with a BMI less than 25 and a FPG less than 86 mg/dL.
The investigators noted that a high-normal FPG value alone may not be a good enough marker for type 2 diabetes risk, since more than half of the subjects in the study had an FPG or more than 90 mg/dL, but the incident rate of diabetes was only 2.3 among this subgroup. Instead, an individualized risk marker that includes FPG, BMI and triglycerides levels might serve as a better screening instrument they suggested.
“Although the study reported by Tirosh et al. deals only with men, there is no reason to believe that the lessons from the study are sex specific,” wrote Ronald A. Arky, M.D., of the Harvard Medical School in an accompanying editorial. “Fasting plasma glucose levels in the high-normal range (91 to 99 mg/dL) in young men and women warrant counseling with regard to weight and lifestyle, as well as an assessment of the lipid profile.”
Primary source: New England Journal of Medicine
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