Risk of Future Diabetes in Japanese People with High-normal Fasting Plasma Glucose Levels: A 4-Year Follow-up Study

Objective There is no definite consensus regarding the treatment and guidance for individuals with high-normal fasting plasma glucose levels (FPG;100-109 mg/dL). The present study aimed to determine the risk factors for future diabetes in Japanese people with high-normal FPG. Methods Retrospective cohort studies were conducted from 2008 to 2012, including 15,097 individuals who underwent medical examinations. First, the participants were divided into normal FPG (n=13,065) and high-normal FPG (n=2,032) groups to compare the diabetes incidence. Second, the high FPG group was divided into diabetes onset (n=133) and non-diabetes onset (n=1,899) groups to compare the baseline values. Third, to determine the risk factors for future diabetes in the high-normal FPG group, multivariate analyses were conducted. Results The cumulative incidence during the mean follow-up of 4 years was 94/13,065 (0.72%) and 133/2,032 (6.55%) in the normal FPG and high-normal FPG groups, respectively. Within the high-normal FPG group, the baseline body mass index, waist circumference, triglycerides, FPG, alanine aminotransferase (ALT), and gamma-glutamyl transferase were significantly higher and high-density lipoprotein cholesterol (HDL-C) was significantly lower in the diabetes onset group than in the non-diabetes onset group. Obesity, abdominal obesity, hypertriglyceridemia, low HDL-C, and high ALT were significant risk factors for diabetes according to a multivariate analysis. Conclusion The high-normal FPG group had a higher risk of diabetes than the normal FPG group, particularly when accompanied with obesity, abdominal obesity, hypertriglyceridemia, low HDL-C, and high ALT. Thus, this high risk group should receive appropriate guidance for lifestyle changes to avoid developing diabetes at an early stage.