Trajectories of fasting glucose and glycated haemoglobin in obese and non-obese incident diabetes: Results from two large cohort studies

Abstract

Aims: Diabetes development mechanisms vary by weight status. We aimed to compare cardiometabolic risk and characterize fasting plasma glucose (FPG) and glycated haemoglobin (HbA1c) trajectories before diagnosing type 2 diabetes in individuals with/without obesity. Methods: Data from the China Health and Retirement Longitudinal Study (CHARLS) and English Longitudinal Study of Ageing (ELSA) were analysed. Participants without diabetes and with a body mass index of 18.5-40 kg/m2 at baseline were included. Incident diabetes was ascertained by self-reported physician diagnosis and/or antidiabetic drug use, FPG ≥126 mg/dl and/or HbA1c ≥6.5%. The difference in the FPG/HbA1c trajectory before the diabetes diagnosis in participants with/without obesity was examined using mixed-effects models. Results: Among 11 925 eligible participants, 1361 incident diabetes cases (mean age: 61.4 years; male: 46.2%) were identified within 15 years of follow-up. Obese diabetes showed higher levels of diastolic blood pressure and C-reactive protein at diagnosis than non-obese diabetes. Mixed-effects models indicated the difference in the FPG trajectory before diagnosis by weight status was non-significant with a slope difference of 0.149 mg/dl (SE = 0.642, p =.816, CHARLS) and 0.013 mg/dl (SE = 0.013, p =.337, ELSA). However, obese diabetes showed a steep increase in HbA1c before diagnosis with a slope difference of 0.036% (SE = 0.016, p =.021) in the CHARLS and 0.032% (SE = 0.014, p =.027) in the ELSA, respectively. Sex-stratified analyses showed that the difference in HbA1c trajectory before the diabetes diagnosis by weight status was only significant in males. Conclusions: Obese and non-obese diabetes developments may share a similar FPG but distinct HbA1c trajectory. Obese diabetes interventions require more attention to cardiometabolic risks. Moreover, studies addressing weight/sex-related differences in diabetes aetiologies and treatments are warranted.