Patterns of trajectories of glycated hemoglobin, fasting plasma glucose, and body mass index until the first clinic visit: the real-world history of type 2 diabetes using repeated health checkup data of Japanese workers.

Background: There is a lack of evidence regarding the trajectories of type 2 diabetes until the first clinic visit, including the untreated period after diagnosis.

Objective: We aimed to determine the real-world history of type 2 diabetes until the first clinic visit, including the untreated duration, and to assess the effective timing of the therapeutic intervention.

Methods: A total of 23,622 nondiabetic Japanese workers with a mean (SD) age of 38.8 (11.5) years were retrospectively followed from 2008 to 2022 for annual health checkups. The trajectories of glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), and body mass index (BMI) until the first clinic visit in diabetes individuals were determined. ROC analysis was performed to assess the contribution of each measure to the first visit.

Results: During a median follow-up of 12.0 years, 1,725 individuals developed type 2 diabetes, of whom 532 individuals visited clinics. HbA1c and FPG trajectories steeply rose in the year before the first clinic visit after their progressive upward trends. ROC analysis showed cutoff values for each measure. As the untreated duration increased, glycemia increased and BMI decreased among individuals who visited clinics.

Conclusions: To prevent the initial worsening of diabetes, early therapeutic intervention is necessary during the increasing trends before the steep rise in glycemia, regardless of the degree of obesity. HbA1c ≥6.5% (47.5 mmol/mol) and an HbA1c ≥0.2% (2.2 mmol/mol)/year increase may be an effective timing for therapeutic intervention.