Trends of HbA1c and BMI in People with Type 2 Diabetes: A Japanese Claims-Based Study.

Introduction: Obesity prevalence has increased in Japan in recent years. Given the strong association of obesity with poor glycemic control, and increased risk of type 2 diabetes (T2D) with central obesity, this study describes the current trends and relationships between glycated hemoglobin (HbA1c), body mass index (BMI), and waist circumference in the Japanese people with T2D.

Methods: This was a retrospective, cross-sectional study of people with T2D who had at least one recorded HbA1c and BMI (or waist circumference) value in the Japan Medical Data Center Claims database. Five annual cohorts of the study population were formed between January 2017 and December 2021. Annual trends of HbA1c across BMI categories (obesity class I [≥ 25 ~  < 30 kg/m²]-IV [≥ 40 kg/m²]) and in people with central obesity (waist circumference: ≥ 85 cm in men; ≥ 90 cm in women) were described by sex and age groups.

Results: Overall, 106,089 people with T2D (HbA1c and BMI data: 106,079; HbA1c and waist circumference data: 105,424) were included, with the majority of people belonging to obesity class I (range: 39.7-40.6%) and obesity class II (range: 16.2-17.7%) categories across all annual cohorts. People in higher BMI categories had higher mean HbA1c, with > 50% of people with T2D in obesity class I-IV (54.8-56.5%) having HbA1c ≥ 7%. Between 2017 and 2021, BMI and waist circumference increased in the age group 18-44 years. More than 50% of people with T2D and central obesity in both sexes and people of age group 18-44 years across obesity class I-IV or with central obesity had HbA1c ≥ 7%.

Conclusion: More than half of the people with T2D belonging to obesity class I-IV or central obesity had poor glycemic control (HbA1c ≥ 7%), especially in the 18-44 age group. This highlights the need for body weight management for better glycemic control in relatively young Japanese people with T2D and obesity.