In a study published in the June, 2008 issue of The American Journal of Medicine the cut-off level for determining diabetes was again challenged. After looking at 46, 578 members of Kaiser Permanente it was found that subjects developed diabetes at a rate of 1% per year. Subjects were assigned to 1 of 4 categories of blood sugar levels (<85, 85-89, 90-94, or 95-99 mg/dl). They were followed for 81 months.
The strong independent association between the level of normal fasting plasma glucose and the incidence of diabetes after controlling for other risk factors (i.e. body mass index, blood pressure, lipids, smoking, cardiovascular disease and hypertension) suggests that diabetes risk increases as fasting plasma glucose increases, even within the currently accepted normal range. For example, for each mg. per deciliter of fasting plasma glucose diabetes risk was increased by 6%. Subjects with glucose levels of 95-99 were 2.33 times more likely to develop diabetes. Subjects in the 90-94 mg/dl group were 49% more likely to progress to diabetes.
The study had several limitations. First, diabetes was defined by a single fasting plasma glucose greater than 125 mg/dl. The American Diabetes Association recommends two fasting blood sugars. Second, they cannot conclude that higher fasting plasma glucose with the normal range actually causes diabetes, they can only report the strong independent association. Third, it is possible that risk factors that were not included such as insulin resistance and family history of diabetes would have accounted for some of the differences seen. Fourth, there was no randomization.
These results demonstrate the increased risk of diabetes extends well below the ADA’s current maximum limit of normal plasma glucose of 99 mg/dl. The study group was large. Future studies need to overcome the identified limitations leading us to a more conclusive cut-off point that represents the greatest risk of diabetes diagnosis.
Kathy Shattler received her Master of Science degree from Michigan State University in E. Lansing Michigan in Human Nutrition. Her twenty-two years of practice includes holding positions as a Lecturer, Chief Clinical Dietitian and Program Manager. Kathy is the Founder of Nutri-Care Consulting and is currently the Nutrition Director of www.CEU4U.COM, an online continuing education management company for Registered Dietitians and Dietetic Technicians.