Excess body weight affects HbA1c progression irrespective of baseline HbA1c levels in Japanese individuals: a longitudinal retrospective study

Abstract

Purpose/aim: Obese individuals with normal HbA1c levels and low-body-weight individuals with high-normal HbA1c levels are frequently encountered in clinical settings, but the effects of these phenotypes on the onset of diabetes are poorly understood. Therefore, we addressed this issue in a longitudinal study. Materials and methods: We analyzed clinical parameters, including body mass index (BMI) and HbA1c levels, in 5325 non-diabetic Japanese people aged 20–75 years who underwent four medical checkups between 1999 (baseline) and 2007. The subjects were then classified into six baseline BMI categories, each of which was divided into two HbA1c groups, resulting in a total of 12 groups. Results: In 405 obese subjects with a normal baseline HbA1c (BMI ≥27.0 kg/m², HbA1c 5.2–5.6%), the mean HbA1c level increased during the study period, and 50.9% developed prediabetes/diabetes. In contrast, in 77 low-body-weight subjects with a high-normal baseline HbA1c (BMI ≤18.9 kg/m², HbA1c 5.7–6.4%), the mean HbA1c level remained constant. Similar changes occurred in the other groups during the study, resulting in a linear increase in HbA1c levels with increasing BMI. Conclusion: Our results suggest that approximately half of the obese individuals with HbA1c in the normal range develop prediabetes or diabetes within 8 years, whereas low-body-weight individuals with high-normal HbA1c are less likely to exhibit worsening in glycemia. Thus, excess body weight may be the primary therapeutic target to prevent the early onset of diabetes, regardless of the individual’s HbA1c.

• Body mass index
• diabetes
• HbA1c
• obesity
• prediabetes

Declaration of interest

This research program was not supported by specific grants from any funding agency in the public or commercial sectors. The authors report no potential conflicts of interest. K. N. and K. S. designed the study. K. S. collected the data. K. N. analyzed the data and evaluated the literature. K. N. wrote the first draft of the manuscript. All authors reviewed and edited the manuscript, and approved the final version for publication.