Incidence and risk factors of type 2 diabetes mellitus in individuals with different fasting plasma glucose levels

OBJECTIVE: Our aim was to examine the incidence and risk factors of type 2 diabetes mellitus (T2DM) among individuals with different fasting plasma glucose (FPG) levels. METHODS: According to the first FPG value recorded between January 2006 and December 2017, individuals without T2DM (FPG <7 mmol/L) were divided into three groups: normal fasting glucose (NFG, FPG < 5.6 mmol/L), slightly impaired fasting glucose (IFG(low), 5.6 mmol/L ⩽ FPG < 6.1 mmol/L), and severely impaired fasting glucose (IFG(high), 6.1 mmol/L ⩽ FPG < 7.0 mmol/L). Physical examination results, blood biochemical indicators, and questionnaire survey data were collected and the T2DM incidence was examined during the follow-up period. A Cox regression model was used to analyze the T2DM risk factors in the three groups. RESULTS: A total of 44,852 individuals (55.33% men) were included in our study. During the follow-up period (mean follow-up time: 3.73 ± 0.01 years), 2912 T2DM cases occurred. The T2DM incidence rate of the NFG, IFG(low), and IFG(high) groups were 1.5%, 22.2%, and 43.8%, respectively (p < 0.05). In the NFG group, the risk factors for T2DM were older age, overweight, obesity, hypertension, hyperuricemia, and increased estimated glomerular filtration rate (eGFR); the protective factors were female sex and high high-density lipoprotein cholesterol (HDL-C). In the IFG(low) group, the risk factors for T2DM were older age, overweight, obesity, hypertension, and high total cholesterol (TC); the protective factors were increased triglyceride, low-density lipoprotein cholesterol (LDL-C), and HDL-C. In the IFG(high) group, the risk factors for T2DM were older age, obesity, high eGFR, and high TC; the protective factors were female sex, hyperuricemia, high LDL-C, and high HDL-C (all, p < 0.05). CONCLUSIONS: The increased T2DM rates were associated with increased FPG. Risk factors for T2DM vary in the NFG, IFG(low), and IFG(high) groups.