Background: Pre-diabetes (pre-DM) increases the risk of developing type 2 diabetes mellitus (T2DM). The incidence of progression from pre-DM to T2DM varies in different ethnic populations.

Objective: To examine the rate of progression from pre-DM to T2DM in a Thai population.

Materials and Methods: This was a cohort study involving participants with pre-DM, diagnosed according to the results of fasting plasma glucose (FPG) and plasma glucose levels two hours after a 75-g oral glucose tolerance test (OGTT) (2-h PG), including IFG+/IGT–, defined by an FPG of 100 to 125 mg/dL (IFG+) and a normal 2-h PG of less than 140 mg/dL (IGT–); IFG–/IGT+, defined by a normal FPG of less than 100 mg/dL (IFG–) and a 2-h PG of 140 to 199 mg/dL (IGT+), and IFG+/IGT+. Each participant was followed-up until diabetes developed or for three years. The incidence of progression to T2DM was calculated every year until the 3-year follow-up period.

Results: Three hundred twenty-five pre-DM participants were enrolled and classified into the following categories: IFG+/IGT– (22.5%), IFG–/IGT+ (44.3%), and IFG+/IGT+ (33.2%). During the 3-year follow-up period, 63 of 325 (19.4%) participants developed T2DM. The incidence of progression to T2DM was 3.1%, 5.7%, and 11.8% at 1, 2, and 3 years, respectively. The mean time to progression to T2DM was 25.5 months. When comparing between subgroups of pre-DM, the IFG–/IGT+ or IFG+/IGT+ subgroups had a higher chance of developing T2DM than the IFG+/IGT– subgroup (p<0.05). Some risk factors, which were a family history of T2DM in first-degree relatives, FPG of 110 mg/dL or more, and an HbA1C of 6.0% or greater were significantly associated with the progression of T2DM in univariate analysis (p<0.05). However moderate-intensity exercise and diabetes self-management education (DSME) attainment were the protective factors (p<0.05).

Conclusion: Almost one-fifth of the participants with pre-DM progressed to T2DM within three years. The annual incidence of DM development was 3.1%, 5.7%, and 11.8% at 1, 2, and 3 years, respectively. People with FPG of 110 mg/dL or more, and an HbA1C of 6.0% or higher, or IGT or combined IGT&IFG should be screened for DM more frequently, using FPG and HbA1C, perhaps every three to six months, especially in those with a family history of T2DM in first-degree relatives. Otherwise, lifestyle modification should be strongly emphasized to prevent development of T2DM in these people.

Keywords: Pre-diabetes, Glucose tolerance test, Diabetes mellitus

DOI: doi.org/10.35755/jmedassocthai.2021.05.12099

Received 27 December 2020 | Revised 21 February 2021 | Accepted 23 February 2021