Clinical Characteristics of People with Newly Diagnosed Type 2 Diabetes between 2015 and 2016: Difference by Age and Body Mass Index.

Background: We evaluated the clinical characteristics of insulin resistance and β-cell dysfunction in newly diagnosed, drug-naive people with type 2 diabetes by analyzing nationwide cross-sectional data.

Methods: We collected the clinical data of 912 participants with newly diagnosed diabetes from 83 primary care clinics and hospitals nationwide from 2015 to 2016. The presence of insulin resistance and β-cell dysfunction was defined as a homeostatic model assessment of insulin resistance (HOMA-IR) value ≥2.5 and fasting C-peptide levels <1.70 ng/mL, respectively.

Results: A total of 75.1% and 22.6% of participants had insulin resistance and β-cell dysfunction, respectively. The proportion of participants with insulin resistance but no β-cell dysfunction increased, and the proportion of participants with β-cell dysfunction but no insulin resistance decreased as body mass index (BMI) increased. People diagnosed with diabetes before 40 years of age had significantly higher HOMA-IR and BMI than those diagnosed over 65 years of age (HOMA-IR, 5.0 vs. 3.0; BMI, 28.7 kg/m² vs. 25.1 kg/m²). However, the β-cell function indices were lower in people diagnosed before 40 years of age than in those diagnosed after 65 years of age (homeostatic model assessment of β-cell function, 39.3 vs. 64.9; insulinogenic index, 10.3 vs. 18.7; disposition index, 0.15 vs. 0.25).

Conclusion: We observed that the main pathogenic mechanism of type 2 diabetes is insulin resistance in participants with newly diagnosed type 2 diabetes. In addition, young adults with diabetes are more likely to have higher insulin resistance with obesity and have higher insulin secretory defect with severe hyperglycemia in the early period of diabetes than older populations.